Rebound in epidemic control: How misaligned vaccination timing amplifies infection peaks

TL;DR

This paper investigates how poorly timed vaccination campaigns can unintentionally cause larger subsequent infection peaks, emphasizing the importance of strategic timing in epidemic control.

Contribution

It reveals the counter-intuitive rebound phenomenon caused by misaligned vaccination timing and identifies optimal vaccination strategies for COVID-19.

Findings

Improper vaccination timing can lead to more severe second infection peaks.

Two optimal vaccination strategies are identified: early rapid vaccination and delayed slower vaccination.

Strategic timing of vaccination is crucial for effective epidemic control.

Abstract

In this study, we explore the dynamic interplay between the timing of vaccination campaigns and the trajectory of disease spread in a population. Through comprehensive data analysis and modeling, we have uncovered a counter-intuitive phenomenon: initiating a vaccination process at an inopportune moment can paradoxically result in a more pronounced second peak of infections. This "rebound" phenomenon challenges the conventional understanding of vaccination impacts on epidemic dynamics. We provide a detailed examination of how improperly timed vaccination efforts can inadvertently reduce the overall immunity level in a population, considering both natural and vaccine-induced immunity. Our findings reveal that such a decrease in population-wide immunity can lead to a delayed, yet more severe, resurgence of cases. This study not only adds a critical dimension to our understanding of vaccination strategies in controlling pandemics but also underscores the necessity for strategically timed interventions to optimize public health outcomes. Furthermore, we compute which vaccination strategies are optimal for a COVID-19 tailored mathematical model, and find that there are two types of optimal strategies. The first type prioritizes vaccinating early and rapidly to reduce the number of deaths, while the second type acts later and more slowly to reduce the number of cases; both of them target primarily the elderly population. Our results hold significant implications for the formulation of vaccination policies, particularly in the context of rapidly evolving infectious diseases.