The MIDAS Webinar Series features research by MIDAS members, and is open to the public.
Date: Friday, December 15, 2023
Speaker: Sophie Larsen
Bio:
Sophie Larsen is a PhD. Candidate in the Program in Ecology, Evolution, and Conservation Biology at the University of Illinois at Urbana-Champaign, working under the guidance of Pamela Martinez. Their research focuses on the impact of host heterogeneity on infectious disease dynamics at the population level. Previously, they earned a Master of Science in Mathematics from the University of Illinois and a Bachelor of Science in Mathematics from the University of Washington.
Abstract:
SARS-CoV-2 vaccines were developed at unprecedented speed, yet rollout disparities and the impact on disease control are not well characterized. In the context of socioeconomic (SES) disparity, the immune landscape of the population may be diverse in both vaccine history and variants of concern. Considering this heterogeneity is crucial because prior exposure could impact adaptive immune response to new infections. We aimed to understand impacts on disease control from (1) first-dose vaccination trends and disparities at a global scale and (2) booster vaccination with bivalent or monovalent formulations in low and middle income countries (LMICs). Using data from 161 countries/territories and 58 states, we first characterized temporal trends of vaccination at the national and subnational level and evaluated the impact on disease outcomes using mathematical models. We then implemented variant- and vaccine-specific SES-stratified transmission models for three LMICs: India, Ecuador, and Malaysia. We tracked immune history of individual hosts through historical SARS-CoV-2 waves, culminating in a booster campaign. Our results show that there are widespread national and subnational SES vaccination disparities. Unexpectedly, timing of initial rollout affects disease outcomes more substantially than final coverage or degree of SES disparity – and timing is not associated with wealth inequality or GDP per capita. Using the variant-specific model, we also characterized the historical landscape of immunity in India, Ecuador, and Malaysia in the context of different booster formulations, finding that deaths averted from boosting have limited sensitivity to booster design and efficacy. We conclude that improving early rollout timing is accessible for most countries, compared to increasing overall coverage or mitigating SES disparities. As booster vaccines are developed, rapid rollout should be prioritized over the type of booster implemented. In regions where acquiring new vaccine stock is challenging, boosters tailored towards historical variants can still avert a considerable portion of cases and deaths.