Vaccination to mitigate climate-driven disruptions to malaria control in Madagascar

INTRODUCTION: Extreme weather events, such as tropical cyclones, interrupt public health activities, threatening global progress toward malaria control. The increasing intensity of tropical cyclones makes this a growing challenge, as malaria-endemic countries include large cyclone-vulnerable populations. Limited data, however, are available to assess the impacts of these disruptions on disease burden. RATIONALE: Using data from a prospective cohort study in southeast Madagascar with malaria infection observations before and after major tropical cyclones in 2022 and 2023 (n = 20,718), we derived estimates of the force of infection in the aftermath of these storms across localities reflecting a range of infection intensity. We then used mathematical models parameterized with estimates of the duration and efficacy of the range of available malaria control tools (e.g., mass drug administration or seasonal malaria chemoprophylaxis) to quantify the potential for applying additional prevention strategies, including vaccination, to mitigate climate-mediated disruptions. RESULTS: Because of their shorter half-life, we find that brief (i.e., <1 month) discontinuities in standard intervention activities such as chemoprophylaxis result in rapid rebounds in infection, an outcome that is robust to sources of uncertainty in estimates of infection rate. Among intervention options, vaccination—newly available for malaria—can be particularly effective at mitigating the impacts of temporal gaps in the coverage of other prevention interventions. By modeling the deployment of antimalarial vaccination in a cyclone-vulnerable setting, we identified an approximate halving of the number of symptomatic infections expected in the wake of a disruption when sufficient coverage (e.g., >70%) is attained for a vaccine with efficacy similar to that reported for the recently approved R21 malaria vaccine. CONCLUSION: Our results demonstrate the benefit of considering disruptions to malaria control measures when evaluating intervention recommendations in high malaria burden, climate-vulnerable geographies. We quantified the effects of a range of available interventions for malaria and identified newly available malaria vaccines as having considerable potential in mitigating these risks. Our data suggest that the effects of climate on disease burden via disruption of health care will be an important element of how climate change shapes global health and emphasize the importance of discontinuities as a challenge to global health progress generally.