Optimal annual COVID-19 vaccine boosting dates following previous booster vaccination or breakthrough infection

COVID-19 booster vaccinations mitigate transmission and reduce the morbidity and mortality associated with infection. However, the optimal date for booster administration remains uncertain. Geographic variation in infection rates throughout the year make it challenging to intuit the best yearly booster administration date to effectively prevent infection, and also challenging to provide best guidance in how to alter booster administration in response to a breakthrough infection. Therefore, we leverage longitudinal antibody and reinfection probabilities with spatiotemporal projections of COVID-19 incidence to develop a geographically-informed approach to optimizing the timing of booster vaccination. Additionally, we assess the delay in booster vaccination that is warranted following breakthrough infections whenever they occur during the year, enabling an approach that acknowledges and respects diverse immune statuses, thereby addressing a substantial barrier to uptake. Our results provide guidance for individual decision-making and healthcare provider recommendations, as well as optimal public health policies.