Quantifying the Impact of Targeted Vaccine Distribution on Polio Outbreak Response Outcomes

Abstract

Polio, a paralytic infectious disease, remains a pressing global health issue, particularly with the rise of circulating vaccine-derived poliovirus (cVDPV) and recurrent outbreaks in regions with under-immunized children. Prior research has indicated that prioritizing vaccination for under-immunized children during outbreak responses can significantly reduce the incidence of paralytic cases and curtail outbreaks with fewer vaccination rounds compared to a generalized approach targeting children regardless of immunity levels. However, individuals’ immunity levels are challenging to observe in practice, which presents a challenge for prioritizing vaccine allocation. Instead, prioritizing vaccines based on vaccination history, while an imperfect measure of immunity, may be a practical and promising strategy. In this study, we systematically assess the effects of vaccine distribution strategies based on children’s vaccination histories on polio outbreak outcomes. Using a compartmental simulation model, we project poliovirus transmission dynamics across varying scenarios, including distinct vaccine allocation schemes by vaccination history, vaccination campaign coverage (i.e., proportion of the target population planned for vaccination), and vaccination campaign timeliness (i.e., time elapsed between outbreak detection and vaccination initiation). We will compare outcomes in terms of (i) outbreak size (i.e., cumulative paralytic cases within the prediction period), (ii) time to outbreak resolution, and (iii) total vaccine doses required to achieve containment. Additionally, we evaluate the potential added value of using vaccination history as a guiding metric for vaccine allocation, relative to an ideal scenario where immunity levels are assumed to be known.