Mark Jit

Chair and Professor of the Department of Global and Environmental Health

Professional overview

Mark Jit is the inaugural chair and a professor in the Department of Global and Environmental Health. He was formerly head of the Department of Infectious Disease Epidemiology & Dynamics and co-director of the Global Health Economics Centre (GHECO) at the London School of Hygiene & Tropical Medicine (LSHTM). He holds honorary appointments at LSHTM as well as the University of Hong Kong (HKU) and the National University of Singapore (NUS).

Dr. Jit’s research focuses on epidemiological and economic modeling of vaccines to support evidence-based public health decision making. He has published papers covering a range of vaccine-preventable or potentially vaccine-preventable diseases including COVID-19, measles, HPV, pneumococcus, rotavirus, influenza, Group B Streptococcus, dengue, EV71 and RSV as well as methodological papers advancing the ways vaccines are evaluated. This work has influenced many of the major changes to immunization policy in countries around the world. Dr. Jit has served on a number of expert advisory committees in the UK as well as for international organizations such as the World Health Organization. He also organises or contributes to academic and professional courses on vaccine modeling, economics and decision science around the world.

Dr. Jit received his BSc and PhD in Mathematics from University College London, specializing in mathematical biology, and a Master of Public Health degree from King’s College London.

Visit Dr. Jit's Google Scholar's page to learn more about his research portfolio.

Education

BSc, Mathematics, University College London

PhD, Mathematics, University College London

MPH, Public Health, King's College London

Honors and awards

Clarivate Highly Cited Researcher (20222023)

Fellow of the Academy of Medical Sciences (2023)

Training Fund Award, Health Protection Agency (2007)

Andrew Rosen Prize, University College London (1999)

Institute of Mathematics and its Applications Award (1998)

Departmental Research Studentship, University College London (1998)

Student Union Commendation, University College London (1997)

Fillon Prize, University College London (1996)

Pathfinder Award, University College London (1995)

Publications

Publications

A systematised review and evidence synthesis on the broader societal impact of vaccines against Salmonella

Demirtas, E. D., Barnard, R., Lee, J., & Jit, M. (n.d.).

Publication year

2025

Journal title

npj Vaccines

Volume

10

Issue

1

10.1038/s41541-024-01034-4

Abstract

Abstract

Vaccines against Salmonella Typhi are available, while vaccines against invasive non-typhoidal Salmonella are in development. Investments in vaccine development and introduction need to be informed by a full value of vaccines assessment, including consideration of broader societal impacts of salmonellae disease. We reviewed literature on these broader impacts in low- and middle-income countries to inform a conceptual framework. We found 16 studies relevant to Salmonella, but only one study on non-typhoidal Salmonella. Despite variations in study design, methodology, and study quality, salmonellae infections were largely associated with negative broader societal impacts, including detriments in childhood physical development (very weak association), childhood educational development (strong to very strong association), household security (moderate association), public health spending (moderate association), and national income (moderate to strong association). Study quality was low for all impacts except childhood physical development. There were no studies measuring economic impact of antimicrobial resistance, changes in household behaviour or health inequalities.

A vaccine chatbot intervention for parents to improve HPV vaccination uptake among middle school girls: a cluster randomized trial

Hou, Z., Wu, Z., Qu, Z., Gong, L., Peng, H., Jit, M., Larson, H. J., Wu, J. T., & Lin, L. (n.d.).

Publication year

2025

Journal title

Nature Medicine

10.1038/s41591-025-03618-6

Abstract

Abstract

Conversational artificial intelligence, in the form of chatbots powered by large language models, offers a new approach to facilitating human-like interactions, yet its efficacy in enhancing vaccination uptake remains under-investigated. This study assesses the effectiveness of a vaccine chatbot in improving human papillomavirus (HPV) vaccination among female middle school students aged 12–15 years across diverse socioeconomic settings in China, where HPV vaccination is primarily paid out-of-pocket. A school-based cluster randomized trial was conducted from 18 January to 31 May 2024. The study included 2,671 parents from 180 middle school classes stratified by socioeconomic setting, school and grade level in Shanghai megacity, and urban and rural regions of Anhui Province. Participants were randomly assigned to either the intervention group (90 classes, 1,294 parents), which engaged with the chatbot for two weeks, or the control group (90 classes, 1,377 parents), which received usual care. The primary outcome was the receipt or scheduled appointment of the HPV vaccine for participants’ daughters. In intention-to-treat analyses, 7.1% of the intervention group met this outcome versus 1.8% of the control group (P < 0.001) over a two-week intervention period. In addition, there was a statistically significant increase in HPV vaccination-specific consultations with health professionals (49.1% versus 17.6%, P < 0.001), along with enhanced vaccine literacy (P < 0.001) and rumor discernment (P < 0.001) among participants using the chatbot. These findings indicate that the chatbot effectively increased vaccination and improved parental vaccine literacy, although further research is necessary to scale and sustain these gains. Clinical trial registration: NCT06227689.

Cost-effectiveness analysis of switching from a bivalent to a nonavalent HPV vaccination programme in China: a modelling study

Gao, M., Hu, S., Zhao, X., You, T., Hong, Y., Liu, Y., Qiao, Y., Jit, M., Zhao, F., & Wang, C. (n.d.).

Publication year

2025

Journal title

The Lancet Regional Health - Western Pacific

Volume

56

10.1016/j.lanwpc.2025.101499

Abstract

Abstract

Background: Several domestically-manufactured nonavalent HPV vaccine candidates are in phase III clinical trials and their future availability may address the current dilemma of insufficient supply and high price of the overseas-manufactured nonavalent HPV vaccine in China. We compare the population-level effectiveness and cost-effectiveness of switching to nonavalent HPV vaccination in China. Methods: We used a previously validated transmission model to project the lifetime costs and effectiveness of five same-vaccine and two mixed-vaccine strategies. Nonavalent HPV vaccines were assumed to be available and meet the production requirements for national vaccination between 2030 and 2050. All women living or projected to be born in China during 2023–2100 were considered. We adopted a societal perspective and determined optimal strategies using cost-effectiveness efficiency frontiers. Findings: Under our pricing assumptions, switching to nonavalent vaccination was always cost-saving compared with maintaining the current bivalent vaccination programme, irrespective of the screening scenarios and the year when nonavalent vaccine was assumed to become available (status quo screening: net cost saving $2589–5211 million; improved screening: net cost saving $1852–3789 million). In the same-vaccine strategies, the optimal strategy changed from “routine nonavalent HPV vaccination with catch-up to age 18” to “switching from bivalent to nonavalent HPV vaccination” if nonavalent vaccination is available after 2035. Compared with the optimal same-vaccine strategy, adopting mixed schedules with bivalent and nonavalent vaccines would further save $1336–4280 million net costs and gain 87,000–833,000 QALYs, depending on the screening scenario and the year when nonavalent vaccine becomes available. Interpretation: Switching from bivalent to nonavalent HPV vaccination is likely to be cost-saving and have a significant impact on reducing the cervical cancer burden in China. Funding: Bill & Melinda Gates Foundation (INV-031449 and INV-003174) and CAMS Innovation Fund for Medical Sciences (CIFMS) (2021-I2M-1-004).

Global socioeconomic inequalities in vaccination coverage, supply, and confidence

Wang, Q., Leung, K., Jit, M., Wu, J. T., & Lin, L. (n.d.).

Publication year

2025

Journal title

npj Vaccines

Volume

10

Issue

1

10.1038/s41541-025-01143-8

Abstract

Abstract

Sustainable Development Goal (SDG) adopted in 2015 aim to reduce inequalities and achieve universal health coverage, including access to essential vaccines for all. Using data from WHO, the Vaccine Confidence Project™, World Bank, and UNDP, we analyzed between-country inequalities in coverage of four vaccines (DTP1, DTP3, MCV1, and POL3), vaccine stock-outs, and vaccine confidence. Economic- and education-related inequalities in coverage (measured by the concentration index) declined from 2015 to 2019, increased in 2020, peaked in 2021, and have declined again since 2022. Inequalities increased continuously in the Region of the Americas. Over 2015–2022, 94 countries/territories reported at least one national level DTP-containing vaccine stock-out. Countries/territories with higher income or education attainment showed lower vaccine confidence. Our study underscores the decrease of inequalities in vaccination coverage following the SDG adoption in most regions, and emphasizes the need to address vaccine stock-outs and strength the vaccine confidence.

Health impact and economic evaluation of the Expanded Program on Immunization in China from 1974 to 2024: a modelling study

Wang, C., Lai, X., Abbas, K., Pouwels, K. B., Zhang, H., Jit, M., & Fang, H. (n.d.).

Publication year

2025

Journal title

The Lancet Public Health

10.1016/S2468-2667(25)00039-8

Abstract

Abstract

Background: The Expanded Program on Immunization (EPI), initiated by WHO in 1974, is a cornerstone of public health. China's EPI covers more than a sixth of the world's population and includes eight routine vaccines with high coverage rates. This study aimed to estimate health and economic impacts of China's EPI over the past 50 years (1974–2024). Methods: This study mathematically modelled the impact of all eight routine vaccines in China's EPI against eight pathogens (measles, pertussis, hepatitis B, tuberculosis, hepatitis A, Japanese encephalitis, meningitis A, and poliomyelitis) based on data availability and their substantial disease burden, particularly accounting for non-linearities in vaccine impact. Health and economic outcomes were determined using mathematical models between a counterfactual scenario without vaccination (vaccine coverage set to zero) and the current vaccination scenario (routine vaccination scheduled at age 0–6 years), based on calendar year and birth cohort approaches. The health impact of China's EPI from 1974 to 2024 was measured in the number of cases, deaths, and disability-adjusted life-years (DALYs) averted. Findings: We estimated that China's EPI averted 703·02 million cases (95% credible interval 699·51–722·80) and 2·48 million deaths (2·14–2·97) in 1974–2024 based on the calendar year approach, equivalent to averting an estimated 160·22 million DALYs (145·05–196·99). Using the birth cohort approach, we predicted 707·41 million cases (703·93–727·03) and 7·01 million deaths (6·95–7·87) averted over the lifetime, corresponding to 279·02 million DALYs (265·78–316·12). From a societal perspective, the aggregated cost of vaccination was estimated to be US$124·06 billion (120·49–127·49), although the benefits amounted to $2417·85 billion (2359·38–2710·35). China's EPI yielded an aggregate benefit–cost ratio of 19·48 (18·82–22·08) from the societal perspective and 8·02 (7·64–8·80) from the provider's perspective. Interpretation: China's EPI has shown remarkable health and economic achievements, contributing to worldwide EPI success in the past 50 years. Further investment in EPI is warranted to sustain coverage and expand vaccine inclusion in China and globally. Funding: Beijing Natural Science Foundation. Translation: For the Chinese translation of the abstract see Supplementary Materials section.

Identification and sizing of the current use cases for seasonal influenza vaccines

Soble, A., Malhame, M., Malvolti, S., Mantel, C., Jit, M., Koh, M., Lambach, P., & Bresee, J. (n.d.).

Publication year

2025

Journal title

Vaccine

10.1016/j.vaccine.2025.127233

Abstract

Abstract

Introduction: Influenza disease continues to have significant global burden. Despite broader use of seasonal influenza vaccines in high resource settings, our understanding of use cases for seasonal influenza vaccines, their relative size, and their relationship to the barriers to adoption in different populations and settings, is limited. This study is a first attempt to identify the use cases for seasonal influenza vaccines to support the design of global influenza vaccination strategies that are better tailored to different implementation contexts and the development of improved influenza vaccines that are more aligned with the different user needs. Methods: By applying a design-based user-centric approach, we implemented a process, including a desk review, a survey, and interviews, to define the current use cases for seasonal influenza vaccines. Results: Nine use cases have been identified as relevant across all different countries and immunization programme designs and validated by experts. Discussion: The identified use cases of seasonal influenza vaccines can support the optimization of vaccination programmes to increase their public health impact. The use cases identified through this work can help signal to policymakers the most important populations and delivery channels to increase the impact of seasonal influenza vaccination programmes and help estimate programmatic requirements necessary for the supportive policy recommendations. The use cases can also support the design of measures aimed at increasing access in low resource settings and coverage in settings where seasonal vaccines are widely used. The use cases can also help to inform the development, of improved influenza vaccines by highlighting the specific product characteristics relevant to their most impactful uses in different programmatic settings.

Population-Wide Depression Incidence Forecasting Comparing Autoregressive Integrated Moving Average and Vector Autoregressive Integrated Moving Average to Temporal Fusion Transformers: Longitudinal Observational Study

Yang, D., Tang, Y., Chan, V. K. Y., Fang, Q., Chan, S. S. M., Luo, H., Wong, I. C. K., Ou, H. T., Chan, E. W. Y., Bishai, D. M., Chen, Y., Knapp, M., Jit, M., Craig, D., & Li, X. (n.d.).

Publication year

2025

Journal title

Journal of medical Internet research

Volume

27

Issue

1

10.2196/67156

Abstract

Abstract

Background: Accurate prediction of population-wide depression incidence is vital for effective public mental health management. However, this incidence is often influenced by socioeconomic factors, such as abrupt events or changes, including pandemics, economic crises, and social unrest, creating complex structural break scenarios in the time-series data. These structural breaks can affect the performance of forecasting methods in various ways. Therefore, understanding and comparing different models across these scenarios is essential. Objective: This study aimed to develop depression incidence forecasting models and compare the performance of autoregressive integrated moving average (ARIMA) and vector-ARIMA (VARIMA) and temporal fusion transformers (TFT) under different structural break scenarios. Methods: We developed population-wide depression incidence forecasting models and compared the performance of ARIMA and VARIMA-based methods to TFT-based methods. Using monthly depression incidence from 2002 to 2022 in Hong Kong, we applied sliding windows to segment the whole time series into 72 ten-year subsamples. The forecasting models were trained, validated, and tested on each subsample. Within each 10-year subset, the first 7 years were used for training, with the eighth year for setting hold-out validation, and the ninth and tenth years for testing. The accuracy of the testing set within each 10-year subsample was measured by symmetric mean absolute percentage error (SMAPE). Results: We found that in subsamples without significant slope or trend change (structural break), multivariate TFT significantly outperformed univariate TFT, vector-ARIMA (VARIMA), and ARIMA, with an average SMAPE of 11.6% compared to 13.2% (P = .01) for univariate TFT, 16.4% (P = .002) for VARIMA, and 14.8% (P = .003) for ARIMA. Adjusting for the unemployment rate improved TFT performance more effectively than VARIMA. When fluctuating outbreaks happened, TFT was more robust to sharp interruptions, whereas VARIMA and ARIMA performed better when incidence surged and remained high. Conclusions: This study provides a comparative evaluation of TFT and ARIMA and VARIMA models for forecasting depression incidence under various structural break scenarios, offering insights into predicting disease burden during both stable and unstable periods. The findings support a decision-making framework for model selection based on the nature of disruptions and data characteristics. For public health policymaking, the results suggest that TFT may be a more suitable tool for disease burden forecasting during periods of stable burden level or when sudden temporary interruption, such as pandemics or socioeconomic variation, impacts disease occurrence.

Social contact patterns and their impact on the transmission of respiratory pathogens in rural China

Liang, Y., You, Q., Wang, Q., Yang, X., Zhong, G., Dong, K., Zhao, Z., Liu, N., Yan, X., Lu, W., Peng, C., Zhou, J., Lin, J., Litvinova, M., Jit, M., Ajelli, M., Yu, H., & Zhang, J. (n.d.).

Publication year

2025

Journal title

Infectious Disease Modelling

Volume

10

Issue

2

Page(s)

439-452

10.1016/j.idm.2024.12.006

Abstract

Abstract

Introduction: Social contact patterns significantly influence the transmission dynamics of respiratory pathogens. Previous surveys have quantified human social contact patterns, yielding heterogeneous results across different locations. However, significant gaps remain in understanding social contact patterns in rural areas of China. Methods: We conducted a pioneering study to quantify social contact patterns in Anhua County, Hunan Province, China, from June to October 2021, when there were minimal coronavirus disease-related restrictions in the area. Additionally, we simulated the epidemics under different assumptions regarding the relative transmission risks of various contact types (e.g., indoor versus outdoor, and physical versus non-physical). Results: Participants reported an average of 12.0 contacts per day (95% confidence interval: 11.3–12.6), with a significantly higher number of indoor contacts compared to outdoor contacts. The number of contacts was associated with various socio-demographic characteristics, including age, education level, income, household size, and travel patterns. Contact patterns were assortative by age and varied based on the type of contact (e.g., physical versus non-physical). The reproduction number, daily incidence, and infection attack rate of simulated epidemics were remarkably stable. Discussion: We found many intergenerational households and contacts that pose challenges in preventing and controlling infections among the elderly in rural China. Our study also underscores the importance of integrating various types of contact pattern data into epidemiological models and provides guidance to public health authorities and other major stakeholders in preparing and responding to infectious disease threats in rural China.

Vaccination strategies against wild poliomyelitis in polio-free settings: Outbreak risk modelling study and cost-effectiveness analysis

Auzenbergs, M., Abbas, K., Peak, C. M., Voorman, A., Jit, M., & O’Reilly, K. M. (n.d.).

Publication year

2025

Journal title

BMJ Global Health

Volume

10

Issue

3

10.1136/bmjgh-2024-016013

Abstract

Abstract

The 2021 importation of wild poliovirus serotype 1 (WPV1) into Malawi with subsequent international spread represented the first WPV1 cases in Africa since 2016. Preventing importations and spread of WPV1 is critical and dependent on population immunity provided through routine immunisation (RI) and supplementary immunisation activities (SIAs). We aim to estimate outbreak risk and costs, given the importation of WPV1 for non-endemic countries in the WHO Africa region. We developed a stochastic mathematical model of polio transmission dynamics to evaluate the probability of an outbreak, expected number of poliomyelitis cases, costs and incremental cost-effectiveness ratios under different vaccination strategies. Across variable RI coverage, we explore three key strategies: RI+outbreak SIAs (oSIAs), RI+oSIAs+annual preventative SIAs (pSIAs) and RI+oSIAs+biennial pSIAs. Results are presented in 2023 USD over a 5year-time horizon from the Global Polio Eradication Initiative (GPEI) and health system perspectives. The annual pSIA strategy has the greatest probability of no outbreaks in comparison to other strategies: under our model assumptions, annual pSIAs result in an 80% probability of no outbreaks when RI coverage is ≥50%. The biennial pSIA strategy requires RI coverage ≥65% to achieve an equivalent risk of no outbreaks. The strategy with no pSIAs requires ≥75% RI coverage to achieve an equivalent risk of no outbreaks. For the health system, when RI coverage is between 35% and 60%, both pSIA strategies are cost-saving. For the GPEI, below 65% RI pSIA strategies are cost-effective, but the biennial pSIA strategy incurs higher costs in comparison to annual pSIAs due to more oSIAs required to stop outbreaks. Prioritisation of pSIAs must balance outbreak risk against implementation costs, ideally favouring the smallest manageable outbreak risk compatible with elimination. We infer that there are few short-Term risks due to population immunity from RI, but without pSIAs, long-Term risks accumulate and can result in outbreaks with the potential for international spread.

A health technology assessment of COVID-19 vaccination for Nigerian decision-makers: Identifying stakeholders and pathways to support evidence uptake

Uzochukwu, B. S., Okeke, C., Shuaib, F., Torres-Rueda, S., Vassall, A., Jit, M., Nonvignon, J., Uzochukwu, A. C., & Ruiz, F. (n.d.).

Publication year

2024

Journal title

Health Research Policy and Systems

Volume

22

Issue

1

10.1186/s12961-024-01158-y

Abstract

Abstract

Background: Nigeria commenced rollout of vaccination for coronavirus disease 2019 (COVID-19) in March 2021 as part of the national public health response to the pandemic. Findings from appropriately contextualized cost–effectiveness analyses (CEA) as part of a wider process involving health technology assessment (HTA) approaches have been important in informing decision-making in this area. In this paper we outline the processes that were followed to identify COVID-19 vaccine stakeholders involved in the selection, approval, funding, procurement and rollout of vaccines in Nigeria, and describe the process routes we identified to support uptake of HTA-related information for evidence-informed policy in Nigeria. Methods: Our approach to engaging with policy-makers and other stakeholders as part of an HTA of COVID vaccination in Nigeria consisted of three steps, namely: (i) informal discussions with key stakeholders; (ii) stakeholder mapping, analysis and engagement; and (iii) communication and dissemination strategies for the HTA-relevant evidence produced. The analysis of the stakeholder mapping uses the power/interest grid framework. Results: The informal discussion with key stakeholders generated six initial policy questions. Further discussions with policy-makers yielded three suitable policy questions for analysis: which COVID-19 vaccines should be bought; what is the optimal mode of delivery of these vaccines; and what are the cost and cost–effectiveness of vaccinating people highlighted in Nigeria’s phase 2 vaccine rollout prioritized by the government, especially the inclusion of those aged between 18 and 49 years. The stakeholder mapping exercise highlighted the range of organizations and groups within Nigeria that could use the information from this HTA to guide decision-making. These stakeholders included both public/government, private and international organizations The dissemination plan developed included disseminating the full HTA results to key stakeholders; production of policy briefs; and presentation at different national and international conferences and peer-reviewed publications. Conclusions: HTA processes that involve stakeholder engagement will help ensure important policy questions are taken into account when designing any HTA including any underpinning evidence generation. Further guidance about stakeholder engagement throughout HTA is required, especially for those with low interest in vaccine procurement and use.

A Scoping Review and Taxonomy of Epidemiological-Macroeconomic Models of COVID-19

Bonnet, G., Pearson, C. A., Torres-Rueda, S., Ruiz, F., Lines, J., Jit, M., Vassall, A., & Sweeney, S. (n.d.).

Publication year

2024

Journal title

Value in Health

Volume

27

Issue

1

Page(s)

104-116

10.1016/j.jval.2023.10.008

Abstract

Abstract

Objectives: The COVID-19 pandemic placed significant strain on many health systems and economies. Mitigation policies decreased health impacts but had major macroeconomic impact. This article reviews models combining epidemiological and macroeconomic projections to enable policy makers to consider both macroeconomic and health objectives. Methods: A scoping review of epidemiological-macroeconomic models of COVID-19 was conducted, covering preprints, working articles, and journal publications. We assessed model methodologies, scope, and application to empirical data. Results: We found 80 articles modeling both the epidemiological and macroeconomic outcomes of COVID-19. Model scope is often limited to the impact of lockdown on health and total gross domestic product or aggregate consumption and to high-income countries. Just 14% of models assess disparities or poverty. Most models fall under 4 categories: compartmental-utility-maximization models, epidemiological models with stylized macroeconomic projections, epidemiological models linked to computable general equilibrium or input-output models, and epidemiological-economic agent-based models. We propose a taxonomy comparing these approaches to guide future model development. Conclusions: The epidemiological-macroeconomic models of COVID-19 identified have varying complexity and meet different modeling needs. Priorities for future modeling include increasing developing country applications, assessing disparities and poverty, and estimating of long-run impacts. This may require better integration between epidemiologists and economists.

An Application of an Initial Full Value of Vaccine Assessment Methodology to Measles-Rubella MAPs for Use in Low- and Middle-Income Countries

Ko, M., Frivold, C., Mvundura, M., Soble, A., Gregory, C., Christiansen, H., Hasso-Agopsowicz, M., Fu, H., Jit, M., Hsu, S., Mistilis, J. J., Scarna, T., Earle, K., Menozzi-Arnaud, M., Giersing, B., Jarrahian, C., Yakubu, A., Malvolti, S., & Amorij, J. P. (n.d.).

Publication year

2024

Journal title

Vaccines

Volume

12

Issue

9

10.3390/vaccines12091075

Abstract

Abstract

Measles and rubella micro-array patches (MR-MAPs) are a promising innovation to address limitations of the current needle and syringe (N&S) presentation due to their single-dose presentation, ease of use, and improved thermostability. To direct and accelerate further research and interventions, an initial full value vaccine assessment (iFVVA) was initiated prior to MR-MAPs entering phase I trials to quantify their value and identify key data gaps and challenges. The iFVVA utilized a mixed-methods approach with rapid assessment of literature, stakeholder interviews and surveys, and quantitative data analyses to (i) assess global need for improved MR vaccines and how MR-MAPs could address MR problem statements; (ii) estimate costs and benefits of MR-MAPs; (iii) identify the best pathway from development to delivery; and (iv) identify outstanding areas of need where stakeholder intervention can be helpful. These analyses found that if MR-MAPs are broadly deployed, they can potentially reach an additional 80 million children compared to the N&S presentation between 2030–2040. MR-MAPs can avert up to 37 million measles cases, 400,000 measles deaths, and 26 million disability-adjusted life years (DALYs). MR-MAPs with the most optimal product characteristics of low price, controlled temperature chain (CTC) properties, and small cold chain volumes were shown to be cost saving for routine immunization (RI) in low- and middle-income countries (LMICs) compared to N&S. Uncertainties about price and future vaccine coverage impact the potential cost-effectiveness of introducing MR-MAPs in LMICs, indicating that it could be cost-effective in 16–81% of LMICs. Furthermore, this iFVVA highlighted the importance of upfront donor investment in manufacturing set-up and clinical studies and the critical influence of an appropriate price to ensure country and manufacturer financial sustainability. To ensure that MR-MAPs achieve the greatest public health benefit, MAP developers, vaccine manufacturers, donors, financiers, and policy- and decision-makers will need close collaboration and open communications.

An overview of the perspectives used in health economic evaluations

Sittimart, M., Rattanavipapong, W., Mirelman, A. J., Hung, T. M., Dabak, S., Downey, L. E., Jit, M., Teerawattananon, Y., & Turner, H. C. (n.d.).

Publication year

2024

Journal title

Cost Effectiveness and Resource Allocation

Volume

22

Issue

1

10.1186/s12962-024-00552-1

Abstract

Abstract

The term ‘perspective’ in the context of economic evaluations and costing studies in healthcare refers to the viewpoint that an analyst has adopted to define the types of costs and outcomes to consider in their studies. However, there are currently notable variations in terms of methodological recommendations, definitions, and applications of different perspectives, depending on the objective or intended user of the study. This can make it a complex area for stakeholders when interpreting these studies. Consequently, there is a need for a comprehensive overview regarding the different types of perspectives employed in such analyses, along with the corresponding implications of their use. This is particularly important, in the context of low-and-middle-income countries (LMICs), where practical guidelines may be less well-established and infrastructure for conducting economic evaluations may be more limited. This article addresses this gap by summarising the main types of perspectives commonly found in the literature to a broad audience (namely the patient, payer, health care providers, healthcare sector, health system, and societal perspectives), providing their most established definitions and outlining the corresponding implications of their uses in health economic studies, with examples particularly from LMIC settings. We then discuss important considerations when selecting the perspective and present key arguments to consider when deciding whether the societal perspective should be used. We conclude that there is no one-size-fits-all answer to what perspective should be used and the perspective chosen will be influenced by the context, policymakers'/stakeholders’ viewpoints, resource/data availability, and intended use of the analysis. Moving forward, considering the ongoing issues regarding the variation in terminology and practice in this area, we urge that more standardised definitions of the different perspectives and the boundaries between them are further developed to support future studies and guidelines, as well as to improve the interpretation and comparison of health economic evidence.

Between now and later: a mixed methods study of HPV vaccination delay among Chinese caregivers in urban Chengdu, China

Yim, V. W. C., Wang, Q., Li, Y., Qin, C., Tang, W., Tang, S., Jit, M., Smith, J. S., Larson, H. J., Tucker, J. D., Li, J., Lin, L., & Wu, D. (n.d.).

Publication year

2024

Journal title

BMC public health

Volume

24

Issue

1

10.1186/s12889-024-17697-6

Abstract

Abstract

Background: Adolescent girls in China have a low HPV vaccination rate. Although vaccination is recommended by the Chinese health authorities, the cost is not covered by the national immunisation programme. Vaccination delay, among other reasons such as supply shortage and poor affordability, may contribute to low uptake. This sequential mixed methods study aimed to identify potential factors of delayed HPV vaccination among Chinese adolescent girls. Methods: Quantitative data about the attitudes and perceptions of HPV vaccination were collected from 100 caregivers of 14–18-year-old girls using an online survey in Chengdu, China. The survey data informed a subsequent qualitative study using four focus group discussions. We conducted a descriptive analysis of the survey data and a thematic analysis of the qualitative data. The findings were interpreted using a health behaviour model adapted from the Health Belief Model and the Andersen’s Behavioural Model for Health Services Use. Results: A total of 100 caregivers – 85 were mothers and 15 were fathers – participated in the survey; 21 caregivers joined focus group discussions. When asked about their intended course of action if the 9vHPV vaccine was out-of-stock, 74% chose to delay until the 9vHPV vaccine is available while 26% would consider 2vHPV or 4vHPV vaccines or seek alternative ways to procure the vaccine. Qualitative results confirmed that caregivers preferred delaying HPV vaccination for adolescent girls. The intent to delay was influenced by systemic barriers such as supply shortage and individual-level factors such as a preference for the 9vHPV vaccine, safety concerns, inadequate health communication, and the belief that adolescents were unlikely to be sexually active. Conclusion: In urban areas, Chinese caregivers’ intent to delay vaccination in favour of 9vHPV vaccine over receiving the more accessible options was influenced by a mix of individual and contextual factors. Focussed health communication strategies are needed to accelerate HPV vaccination among adolescents.

Clinical coding of long COVID in primary care 2020–2023 in a cohort of 19 million adults: an OpenSAFELY analysis

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Publication year

2024

Journal title

EClinicalMedicine

Volume

72

10.1016/j.eclinm.2024.102638

Abstract

Abstract

Background: Long COVID is the patient-coined term for the persistent symptoms of COVID-19 illness for weeks, months or years following the acute infection. There is a large burden of long COVID globally from self-reported data, but the epidemiology, causes and treatments remain poorly understood. Primary care is used to help identify and treat patients with long COVID and therefore Electronic Health Records (EHRs) of past COVID-19 patients could be used to help fill these knowledge gaps. We aimed to describe the incidence and differences in demographic and clinical characteristics in recorded long COVID in primary care records in England. Methods: With the approval of NHS England we used routine clinical data from over 19 million adults in England linked to SARS-COV-2 test result, hospitalisation and vaccination data to describe trends in the recording of 16 clinical codes related to long COVID between November 2020 and January 2023. Using OpenSAFELY, we calculated rates per 100,000 person-years and plotted how these changed over time. We compared crude and adjusted (for age, sex, 9 NHS regions of England, and the dominant variant circulating) rates of recorded long COVID in patient records between different key demographic and vaccination characteristics using negative binomial models. Findings: We identified a total of 55,465 people recorded to have long COVID over the study period, which included 20,025 diagnoses codes and 35,440 codes for further assessment. The incidence of new long COVID records increased steadily over 2021, and declined over 2022. The overall rate per 100,000 person-years was 177.5 cases in women (95% CI: 175.5–179) and 100.5 in men (99.5–102). The majority of those with a long COVID record did not have a recorded positive SARS-COV-2 test 12 or more weeks before the long COVID record. Interpretation: In this descriptive study, EHR recorded long COVID was very low between 2020 and 2023, and incident records of long COVID declined over 2022. Using EHR diagnostic or referral codes unfortunately has major limitations in identifying and ascertaining true cases and timing of long COVID. Funding: This research was supported by the National Institute for Health and Care Research (NIHR) (OpenPROMPT: COV-LT2-0073).

Contribution of vaccination to improved survival and health: modelling 50 years of the Expanded Programme on Immunization

Shattock, A. J., Johnson, H. C., Sim, S. Y., Carter, A., Lambach, P., Hutubessy, R. C., Thompson, K. M., Badizadegan, K., Lambert, B., Ferrari, M. J., Jit, M., Fu, H., Silal, S. P., Hounsell, R. A., White, R. G., Mosser, J. F., Gaythorpe, K. A., Trotter, C. L., Lindstrand, A., … Bar-Zeev, N. (n.d.).

Publication year

2024

Journal title

The Lancet

Volume

403

Issue

10441

Page(s)

2307-2316

10.1016/S0140-6736(24)00850-X

Abstract

Abstract

Background: WHO, as requested by its member states, launched the Expanded Programme on Immunization (EPI) in 1974 to make life-saving vaccines available to all globally. To mark the 50-year anniversary of EPI, we sought to quantify the public health impact of vaccination globally since the programme's inception. Methods: In this modelling study, we used a suite of mathematical and statistical models to estimate the global and regional public health impact of 50 years of vaccination against 14 pathogens in EPI. For the modelled pathogens, we considered coverage of all routine and supplementary vaccines delivered since 1974 and estimated the mortality and morbidity averted for each age cohort relative to a hypothetical scenario of no historical vaccination. We then used these modelled outcomes to estimate the contribution of vaccination to globally declining infant and child mortality rates over this period. Findings: Since 1974, vaccination has averted 154 million deaths, including 146 million among children younger than 5 years of whom 101 million were infants younger than 1 year. For every death averted, 66 years of full health were gained on average, translating to 10·2 billion years of full health gained. We estimate that vaccination has accounted for 40% of the observed decline in global infant mortality, 52% in the African region. In 2024, a child younger than 10 years is 40% more likely to survive to their next birthday relative to a hypothetical scenario of no historical vaccination. Increased survival probability is observed even well into late adulthood. Interpretation: Since 1974 substantial gains in childhood survival have occurred in every global region. We estimate that EPI has provided the single greatest contribution to improved infant survival over the past 50 years. In the context of strengthening primary health care, our results show that equitable universal access to immunisation remains crucial to sustain health gains and continue to save future lives from preventable infectious mortality. Funding: WHO.

Cost-effectiveness of COVID rapid diagnostic tests for patients with severe/critical illness in low- and middle-income countries: A modeling study

Bonnet, G., Bimba, J., Chavula, C., Chifamba, H. N., Divala, T. H., Lescano, A. G., Majam, M., Mbo, D., Suwantika, A. A., Tovar, M. A., Yadav, P., Ekwunife, O., Mangenah, C., Ngwira, L. G., Corbett, E. L., Jit, M., & Vassall, A. (n.d.).

Publication year

2024

Journal title

PLoS Medicine

Volume

21

Issue

7

10.1371/journal.pmed.1004429

COVID-19-related health utility values and changes in COVID-19 patients and the general population: a scoping review

Mao, Z., Li, X., Jit, M., & Beutels, P. (n.d.).

Publication year

2024

Journal title

Quality of Life Research

Volume

33

Issue

6

Page(s)

1443-1454

10.1007/s11136-023-03584-x

Abstract

Abstract

Purpose: To summarise the diverse literature reporting the impact of COVID-19 on health utility in COVID-19 patients as well as in general populations being affected by COVID-19 control policies. Methods: A literature search up to April 2023 was conducted to identify papers reporting health utility in COVID-19 patients or in COVID-19-affected general populations. We present a narrative synthesis of the health utility values/losses of the retained studies to show the mean health utility values/losses with 95% confidence intervals. Mean utility values/losses for categories defined by medical attendance and data collection time were calculated using random-effects models. Results: In total, 98 studies—68 studies on COVID-19 patients and 30 studies on general populations—were retained for detailed review. Mean (95% CI) health utility values were 0.83 (0.81, 0.86), 0.78 (0.73, 0.83), 0.82 (0.78, 0.86) and 0.71 (0.65, 0.78) for general populations, non-hospitalised, hospitalised and ICU patients, respectively, irrespective of the data collection time. Mean utility losses in patients and general populations ranged from 0.03 to 0.34 and from 0.02 to 0.18, respectively. Conclusions: This scoping review provides a summary of the health utility impact of COVID-19 and COVID-19 control policies. COVID-19-affected populations were reported to have poor health utility, while a high degree of heterogeneity was observed across studies. Population- and/or country-specific health utility is recommended for use in future economic evaluation on COVID-19-related interventions.

Effectiveness and efficiency of immunisation strategies to prevent RSV among infants and older adults in Germany: a modelling study

Krauer, F., Guenther, F., Treskova-Schwarzbach, M., Schoenfeld, V., Koltai, M., Jit, M., Hodgson, D., Schneider, U., Wichmann, O., Harder, T., Sandmann, F. G., & Flasche, S. (n.d.).

Publication year

2024

Journal title

BMC Medicine

Volume

22

Issue

1

10.1186/s12916-024-03687-3

Abstract

Abstract

Background: Recently, several novel RSV immunisation products that protect infants and older adults against RSV disease have been licensed in Europe. We estimated the effectiveness and efficiency of introducing these RSV immunisation strategies in Germany. Methods: We used a Bayesian framework to fit a deterministic age-structured dynamic transmission model of RSV to sentinel surveillance and RSV-specific hospitalisation data in Germany from 2015 to 2019. The calibrated model was used to evaluate different RSV intervention strategies over 5 years: long-acting, single-dose monoclonal antibodies (mAbs) in high-risk infants aged 1–5 months; long-acting mAbs in all infants aged 1–5 months; seasonal vaccination of pregnant women and one-time seasonal vaccination of older adults (75 + /65 + /55 + years). We performed sensitivity analysis on vaccine uptake, seasonal vs. year-round maternal vaccination, and the effect of under-ascertainment for older adults. Results: The model was able to match the various RSV datasets. Replacing the current short-acting mAB for high-risk infants with long-acting mAbs prevented 1.1% of RSV-specific hospitalisations in infants per year at the same uptake. Expanding the long-acting mAB programme to all infants prevented 39.3% of infant hospitalisations per year. Maternal vaccination required a larger number to be immunised to prevent one additional hospitalisation than a long-acting mAB for the same uptake. Vaccination of adults older than 75 years at an uptake of 40% in addition to Nirsevimab in all infants prevented an additional 4.5% of all RSV hospitalisations over 5 years, with substantial uncertainty in the correction for under-ascertainment of the RSV burden. Conclusions: Immunisation has the potential to reduce the RSV disease burden in Germany.

Effects of sequential vs single pneumococcal vaccination on cardiovascular diseases among older adults: a population-based cohort study

Tong, X., Gao, L., Wong, I. C., Chan, V. K., Wong, A. Y., Mak, J. C., Yuen, J. K., Jit, M., Hung, I. F., Yiu, K. H., & Li, X. (n.d.).

Publication year

2024

Journal title

International Journal of Epidemiology

Volume

53

Issue

1

10.1093/ije/dyae005

Abstract

Abstract

Background: Recommendations around the use of 23-valent pneumococcal polysaccharide vaccine (PPSV23) and 13-valent pneumococcal conjugate vaccine (PCV13) seldom focus on potential benefits of vaccine on comorbidities. We aimed to investigate whether sequential vaccination with PCV13 and PPSV23 among older adults would provide protection against cardiovascular diseases (CVD) compared with using a single pneumococcal vaccine. Methods: We conducted a Hong Kong-wide retrospective cohort study between 2012 and 2020. Adults aged ≥65 years were identified as receiving either a single or sequential dual vaccination and followed up until the earliest CVD occurrence, death or study end. To minimize confounding, we matched each person receiving a single vaccination to a person receiving sequential vaccination according to their propensity scores. We estimated the hazard ratio (HR) of CVD risk using Cox regression and applied structural equation modelling to test whether the effect of sequential dual vaccination on CVD was mediated via the reduction in pneumonia. Results: After matching, 69 390 people remained in each group and the median (interquartile range) follow-up time was 1.89 (1.55) years. Compared with those receiving a single vaccine, those receiving sequential dual vaccination had a lower risk of CVD [HR (95% CI): 0.75 (0.71, 0.80), P < 0.001]. Post-hoc mediation analysis showed strong evidence that the decreased CVD risk was mediated by the reduction in all-cause pneumonia. Conclusions: Sequential dual pneumococcal vaccination was associated with lower risk of CVD compared with single-dose PCV13 or PPSV23 in older adults. Such additional CVD benefits should be considered when making decisions about pneumococcal vaccination.

Equity impact of HPV vaccination on lifetime projections of cervical cancer burden among cohorts in 84 countries by global, regional, and income levels, 2010–22: a modelling study

Abbas, K., Yoo, K. J., Prem, K., & Jit, M. (n.d.).

Publication year

2024

Journal title

EClinicalMedicine

Volume

70

10.1016/j.eclinm.2024.102524

Abstract

Abstract

Background: While human papillomavirus (HPV) vaccines have been available since 2006, the coverage has varied among countries. Our aim is to analyse the equity impact of HPV vaccination on the lifetime projections of cervical cancer burden among vaccinated cohorts of 2010–22 in 84 countries. Methods: We used WHO and UNICEF estimates of national immunisation coverage for HPV vaccination in 84 countries during 2010–22. We used PRIME (Papillomavirus Rapid Interface for Modelling and Economics) to estimate the lifetime health impact of HPV vaccination on cervical cancer burden in terms of deaths, cases, and disability-adjusted life years (DALYs) averted by vaccination in their respective countries. We generated concentration indices and curves to assess the equity impact of HPV vaccination across 84 countries. Findings: The health impact of HPV vaccination varied across the 84 countries and ranged from Switzerland to Tanzania at 2 to 34 deaths, 4 to 47 cases, and 40 to 735 DALYs averted per 1000 vaccinated adolescent girls over the lifetime of the vaccinated cohorts of 2010–22. The concentration index for the distribution of average coverage during 2010–22 among the 84 countries ranked by vaccine impact was 0.33 (95% CI: 0.27–0.40) and highlights the wide inequities in HPV vaccination coverage. Interpretation: Our findings suggested that countries with a relatively higher cervical cancer burden and thereby a relatively higher need for HPV vaccination had relatively lower coverage during 2010–22. Further, there were significant inequities in HPV vaccination coverage within the Americas, Europe, and Western Pacific regions, and in high- and low-income countries with a pro-advantaged and regressive distribution favouring countries with lower vaccine impact. Funding: Gavi, the Vaccine Alliance; Bill & Melinda Gates Foundation.

Estimating the health effects of COVID-19-related immunisation disruptions in 112 countries during 2020–30: a modelling study

Hartner, A. M., Li, X., Echeverria-Londono, S., Roth, J., Abbas, K., Auzenbergs, M., De Villiers, M. J., Ferrari, M. J., Fraser, K., Fu, H., Hallett, T., Hinsley, W., Jit, M., Karachaliou, A., Moore, S. M., Nayagam, S., Papadopoulos, T., Perkins, T. A., Portnoy, A., … Gaythorpe, K. A. (n.d.).

Publication year

2024

Journal title

The Lancet Global Health

Volume

12

Issue

4

Page(s)

e563-e571

10.1016/S2214-109X(23)00603-4

Abstract

Abstract

Background: There have been declines in global immunisation coverage due to the COVID-19 pandemic. Recovery has begun but is geographically variable. This disruption has led to under-immunised cohorts and interrupted progress in reducing vaccine-preventable disease burden. There have, so far, been few studies of the effects of coverage disruption on vaccine effects. We aimed to quantify the effects of vaccine-coverage disruption on routine and campaign immunisation services, identify cohorts and regions that could particularly benefit from catch-up activities, and establish if losses in effect could be recovered. Methods: For this modelling study, we used modelling groups from the Vaccine Impact Modelling Consortium from 112 low-income and middle-income countries to estimate vaccine effect for 14 pathogens. One set of modelling estimates used vaccine-coverage data from 1937 to 2021 for a subset of vaccine-preventable, outbreak-prone or priority diseases (ie, measles, rubella, hepatitis B, human papillomavirus [HPV], meningitis A, and yellow fever) to examine mitigation measures, hereafter referred to as recovery runs. The second set of estimates were conducted with vaccine-coverage data from 1937 to 2020, used to calculate effect ratios (ie, the burden averted per dose) for all 14 included vaccines and diseases, hereafter referred to as full runs. Both runs were modelled from Jan 1, 2000, to Dec 31, 2100. Countries were included if they were in the Gavi, the Vaccine Alliance portfolio; had notable burden; or had notable strategic vaccination activities. These countries represented the majority of global vaccine-preventable disease burden. Vaccine coverage was informed by historical estimates from WHO–UNICEF Estimates of National Immunization Coverage and the immunisation repository of WHO for data up to and including 2021. From 2022 onwards, we estimated coverage on the basis of guidance about campaign frequency, non-linear assumptions about the recovery of routine immunisation to pre-disruption magnitude, and 2030 endpoints informed by the WHO Immunization Agenda 2030 aims and expert consultation. We examined three main scenarios: no disruption, baseline recovery, and baseline recovery and catch-up. Findings: We estimated that disruption to measles, rubella, HPV, hepatitis B, meningitis A, and yellow fever vaccination could lead to 49 119 additional deaths (95% credible interval [CrI] 17 248–134 941) during calendar years 2020–30, largely due to measles. For years of vaccination 2020–30 for all 14 pathogens, disruption could lead to a 2·66% (95% CrI 2·52–2·81) reduction in long-term effect from 37 378 194 deaths averted (34 450 249–40 241 202) to 36 410 559 deaths averted (33 515 397–39 241 799). We estimated that catch-up activities could avert 78·9% (40·4–151·4) of excess deaths between calendar years 2023 and 2030 (ie, 18 900 [7037–60 223] of 25 356 [9859–75 073]). Interpretation: Our results highlight the importance of the timing of catch-up activities, considering estimated burden to improve vaccine coverage in affected cohorts. We estimated that mitigation measures for measles and yellow fever were particularly effective at reducing excess burden in the short term. Additionally, the high long-term effect of HPV vaccine as an important cervical-cancer prevention tool warrants continued immunisation efforts after disruption. Funding: The Vaccine Impact Modelling Consortium, funded by Gavi, the Vaccine Alliance and the Bill & Melinda Gates Foundation. Translations: For the Arabic, Chinese, French, Portguese and Spanish translations of the abstract see Supplementary Materials section.

Estimating the impact of vaccination: lessons learned in the first phase of the Vaccine Impact Modelling Consortium

Gaythorpe, K. A., Li, X., Clapham, H., Dansereau, E., Fitzjohn, R., Hinsley, W., Hogan, D., Jit, M., Mengistu, T., Perkins, T. A., Portnoy, A., Vynnycky, E., Woodruff, K., Ferguson, N. M., & Trotter, C. L. (n.d.). In Gates Open Research (1–).

Publication year

2024

Volume

8

10.12688/gatesopenres.15556.1

Abstract

Abstract

Estimates of the global health impact of immunisation are important for quantifying historical benefits as well as planning future investments and strategy. The Vaccine Impact Modelling Consortium (VIMC) was established in 2016 to provide reliable estimates of the health impact of immunisation. In this article we examine the consortium in its first five-year phase. We detail how vaccine impact was defined and the methods used to estimate it as well as the technical infrastructure required to underpin robust reproducibility of the outputs. We highlight some of the applications of estimates to date, how these were communicated and what their effect were. Finally, we explore some of the lessons learnt and remaining challenges for estimating the impact of vaccines and forming effective modelling consortia then discuss how this may be addressed in the second phase of VIMC. Modelled estimates are not a replacement for surveillance; however, they can examine theoretical counterfactuals and highlight data gaps to complement other activities. VIMC has implemented strategies to produce robust, standardised estimates of immunisation impact. But through the first phase of the consortium, critical lessons have been learnt both on the technical infrastructure and the effective engagement with modellers and stakeholders. To be successful, a productive dialogue with estimate consumers, producers and stakeholders needs to be underpinned by a rigorous and transparent analytical framework as well as an approach for building expertise in the short and long term.

Evaluating Scope and Bias of Population-Level Measles Serosurveys: A Systematized Review and Bias Assessment

Sbarra, A. N., Cutts, F. T., Fu, H., Poudyal, I., Rhoda, D. A., Mosser, J. F., & Jit, M. (n.d.).

Publication year

2024

Journal title

Vaccines

Volume

12

Issue

6

10.3390/vaccines12060585

Abstract

Abstract

Background: Measles seroprevalence data have potential to be a useful tool for understanding transmission dynamics and for decision making efforts to strengthen immunization programs. In this study, we conducted a systematized review and bias assessment of all primary data on measles seroprevalence in low- and middle-income countries (as defined by World Bank 2021 income classifications) published from 1962 to 2021. Methods: On 9 March 2022, we searched PubMed for all available data. We included studies containing primary data on measles seroprevalence and excluded studies if they were clinical trials or brief reports, from only health-care workers, suspected measles cases, or only vaccinated persons. We extracted all available information on measles seroprevalence, study design, and seroassay protocol. We conducted a bias assessment based on multiple categories and classified each study as having low, moderate, severe, or critical bias. This review was registered with PROSPERO (CRD42022326075). Results: We identified 221 relevant studies across all World Health Organization regions, decades, and unique age ranges. The overall crude mean seroprevalence across all studies was 78.0% (SD: 19.3%), and the median seroprevalence was 84.0% (IQR: 72.8–91.7%). We classified 80 (36.2%) studies as having severe or critical overall bias. Studies from country-years with lower measles vaccine coverage or higher measles incidence had higher overall bias. Conclusions: While many studies have substantial underlying bias, many studies still provide some insights or data that could be used to inform modelling efforts to examine measles dynamics and programmatic decisions to reduce measles susceptibility.

Global vaccine coverage and childhood survival estimates: 1990–2019

Zhang, H., Patenaude, B., Zhang, H., Jit, M., & Fang, H. (n.d.).

Publication year

2024

Journal title

Bulletin of the World Health Organization

Volume

102

Issue

4

Page(s)

276-287

10.2471/BLT.23.290129

Abstract

Abstract

Objective To quantify the association between reduction in child mortality and routine immunization across 204 countries and territories from 1990 to 2019. Methods We used child mortality and vaccine coverage data from the Global Burden of Disease Study. We used a modified child survival framework and applied a mixed-effects regression model to estimate the reduction in deaths in children younger than 5 years associated with eight vaccines. Findings Between 1990 and 2019, the diphtheria–tetanus–pertussis (DTP), measles, rotavirus and Haemophilus influenzae type b vaccines were significantly associated with an estimated 86.9 (95% confidence interval, CI: 57.2 to 132.4) million fewer deaths in children younger than 5 years worldwide. This decrease represented a 24.2% (95% CI: 19.8 to 28.9) reduction in deaths relative to a scenario without vaccines. The DTP and measles vaccines averted 46.7 (95% CI: 30.0 to 72.7) million and 37.9 (95% CI: 25.4 to 56.8) million deaths, respectively. Of the total reduction in child mortality associated with vaccines, 84.2% (95% CI: 83.0 to 85.1) occurred in 73 countries supported by Gavi, the Vaccine Alliance, with an estimated 45.4 (95% CI: 29.8 to 69.2) million fewer deaths from 2000 to 2019. The largest reductions in deaths associated with these four vaccines were in India, China, Ethiopia, Pakistan and Bangladesh (in order of the size of reduction). Conclusion Vaccines continue to reduce childhood mortality significantly, especially in Gavi-supported countries, emphasizing the need for increased investment in routine immunization programmes.