The impact of climate and demographic changes on future chikungunya burden and the potential role of vaccines: a mathematical modelling study

BackgroundChikungunya virus (CHIKV) is an Aedes transmitted arbovirus. Demographic changes coupled with the expanding footprint of the mosquito from climate change have the potential to shift the global burden from the virus. MethodsHere we use projections of human demography and Aedes mosquitoes distribution to estimate baseline and future burden from CHIKV under different climate change scenarios in 178 countries. We then estimate the potential of vaccines to mitigate the growing burden. FindingsWe found that under RCP2.6 (an optimistic climate change scenario), the global population at risk from CHIKV will increase by 30.2% to 5.4 billion individuals. We estimated a 35% increase in annual infections, 49% increase in cases and a 128% increase in deaths. A similar impact was found under the more pessimistic RCP8.5 climate change scenario. In Europe and the Americas, the growing presence of Aedes will drive the growing case burden, with increases in human population size being key elsewhere. Ageing populations will result in major increases in the number of CHIKV-related deaths in all continents outside Africa. Vaccinating 50% of individuals aged 12y+ with a vaccine providing 70% protection against disease and 40% protection against infection would avert 29% of cases and 31% of deaths. InterpretationThese findings highlight how climate change will expand the footprint of CHIKV circulation, while demographic changes will lead to substantially increased case burden in affected countries. Vaccines will be critical to minimising this changing global burden. FundingCEPI