Age-specific chikungunya outbreak response immunisation strategies in Brazil: a modelling study

Sep 29, 2026

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Age-specific chikungunya outbreak response immunisation strategies in Brazil are evaluated using an age-structured transmission dynamic model calibrated with state-level surveillance data. Two licensed vaccines, Ixchiq and Vimkunya, are assessed for strategies targeting ages 1–11, 12–17, 18–59, and ≥60 years across 11 of 27 states. Outcomes include symptomatic cases, deaths, DALYs averted, and NNV under disease-only versus disease-and-infection blocking mechanisms. Results indicate broadly similar vaccine impacts, with adolescents prioritized first and greater symptomatic reductions from vaccinating adults 18–59 years.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages13

Reading Time33 min

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Methods

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Articles Age-specific chikungunya outbreak response immunisation strategies in Brazil: a modelling study Hyolim Kang,a,b,c,∗ Ahyoung Lim,a Andrew Clark,d Felipe J. Colón González,e Hannah Eleanor Clapham,f Jean-Paul Carrera,g,h Jong-Hoon Kim,i Megan Auzenbergs,j Preethi Lakshminarayanan,a Sandra López-Vergès,k So Yoon Sim,l Su Myat Han,b,c Thiago Cerqueira-Silva,a,m Timothy Endy,n Zulma M. Cucunubá,o W John Edmunds,a,b,c Sushant Sahastrabuddhe,c,i,p,q Oliver J. Brady,a,t and Kaja Abbasa,b,c,r,s,t aDepartment of Infectious Disease Epidemiology and Dynamics, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK bSchool of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan cInstitute of Tropical Medicine, Nagasaki University, Nagasaki, Japan dDepartment of Health Services Research and Policy, Faculty of Public Health and Policy, London School of Hygiene & Tropical Medicine, London, UK eData for Science and Health, Wellcome Trust, London, UK fSaw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore gCarson Centre for Health and Ecosystems Research, Darien, Panama hDepartment of Biology, University of Oxford, Oxford, UKiInternational Vaccine Institute, Seoul, South Korea jImperial College London, London, UK kGorgas Memorial Institute for Health Studies, Panama City, Panama lDepartment of Immunization, Vaccines, and Biologicals, World Health Organization, Geneva, Switzerland mLaboratório de Medicina e Saúde Pública de Precisão - Fundação Oswaldo Cruz, Salvador, Brazil nCoalition for Epidemic Preparedness Innovations, Washington, DC, USA oInstitute of Public Health, Pontificia Universidad Javeriana, Colombia pDepartment of Microbiology, College of Medicine, Yonsei University, Seoul, South Korea qCentre International de Recherche en Infectiologie, Université Jean Monnet, Université Claude Bernard Lyon 1, France rPublic Health Foundation of India, New Delhi, India sNational Institute of Infectious Diseases, Japan Institute for Health Security, Tokyo, Japan Summary Background Two chikungunya vaccines, Ixchiq and Vimkunya are licensed. In April 2025, Brazil is the first endemic country to license Ixchiq, but optimal age groups for vaccination remain unclear. Our aim is to model the public health impact of age-specific chikungunya outbreak response immunisation strategies in Brazil and infer broader implications for vaccine use case scenarios in outbreak prone regions. Methods We developed an age-structured transmission dynamic model calibrated with state-level Brazilian surveillance data for 2022 and long-term average annual force of infections. We simulated outbreak response immunisation strategies targeting ages 1–11, 12–17, 18–59, and ≥60 years for Ixchiq and Vimkunya across 11 out of 27 states in Brazil. We assessed vaccine impact by symptomatic cases, deaths, and disability-adjusted life years (DALYs) averted and number needed to vaccinate (NNV) based on vaccine protection against disease only and against both disease and infection. Findings Ixchiq and Vimkunya showed similar vaccine impact. Across strategies, vaccinating children 1–11 years yielded the lowest NNV for both vaccines, whereas vaccinating adults 18–59 years achieved the greatest absolute reduction in symptomatic cases, averting 62.5%(95% Uncertainty Intervals [UI]: 54.2–84.1) of total symptomatic cases with Vimkunya and 66.2%(58.2–86.0) with Ixchiq, under disease and infection blocking mechanism. Vaccinating adults 18–59 years with Ixchiq or Vimkunya yielded similar efficiency, with NNVs to avert a DALY of 339 (39–3412) and 361 (40–3777) respectively, under disease and infection-blocking mechanism. Interpretation Under current licensure, vaccinating adolescents aged 12–17 years first, followed by 18–59 years are efficient strategies, with similar NNVs for both Ixchiq and Vimkunya. If eligibility e

FAQs

Which chikungunya vaccines are evaluated in this modelling study?

The study evaluates two licensed vaccines: Ixchiq and Vimkunya.

How were age groups and outcomes assessed?

Age-specific strategies targeting 1–11, 12–17, 18–59, and ≥60 years were simulated, and impact was measured using symptomatic cases, deaths, DALYs averted, and number needed to vaccinate (NNV).

What vaccination strategy is considered efficient under current licensure?

Under current licensure, vaccinating adolescents aged 12–17 years first, followed by adults aged 18–59 years, is described as an efficient strategy with similar NNVs for both vaccines.

Sep 29, 2026

Uploaded by Aran