Study finds optimal timing of annual COVID-19 booster depends on regional transmission patterns and if/when breakthrough infection has occurred.
Jeffrey Townsend, PhD
An annual COVID-19 vaccination booster that precedes the highest anticipated prevalence in a region but is postponed in the event of a breakthrough infection was calculated to provide a 3-4-fold increase in protection from infection over less tailored seasonal recommendations, in a multi-country analysis incorporating longitudinal antibody and reinfection probabilities with regional projections of COVID-19 incidence.1
"Our analysis demonstrated that optimally timing booster shots can provide a major boost in protection, helping to keep people safer when they're most at risk" said Jeffrey Townsend, PhD, lead study author and Elihu professor of Biostatistics and professor of Ecology and Evolutionary Biology, Yale School of Public Health, New Haven, CT, in a released statement.2
"Breakthrough infections complicate booster timing, but our findings offer a clear solution, added Hayley Hassler, co-author of the study and PhD candidate, School of Chemistry & Biochemistry, Georgia Tech, Atlanta, GA.2
The investigators note that, unlike influenza booster vaccination timed to meet seasonal surges associated with climate, COVID-19 does not follow endemic seasonality."Instead (COVID-19 infections) have been characterized by pandemic surges driven by historical contingencies, early saltations of viral evolution, and wholly naive versus differentially exposed immunological states of population.
"Therefore, an alternate approach to evaluating optimal timing is necessary until there is sufficient accumulation of long-term empirical data on seasonality," Townsend and colleagues propose.
The investigators characterize their study as the first continuous assessment of risk of infection with respect to annual booster vaccination for both people whose most recent exposure is a scheduled booster or a breakthrough infection.The investigators quantified relative monthly probabilities of infection based on seasonal incidence predictions for endemic COVID-19 for 12 regions in the Northern Hemisphere.Their analysis accounted for a lowered risk following vaccination, informed by data on antibody waning associated with the Pfizer-BioNtech booster (BNY162b2).The cumulative yearly probability of infection was calculated for each day of the year.
Annual COVID-19 booster vaccinations timed approximately 2.7 months before the highest anticipated regional prevalence significantly increase protection (3-4 fold) compared to less tailored schedules.
For those experiencing breakthrough infections near their scheduled booster date, delaying the next booster by over 9 months can optimize protection.
The study emphasizes a tailored approach that considers individual infection histories and regional incidence predictions.
"The booster vaccination date on which the cumulative yearly probability of infection is at its lowest represent the optimal year booster vaccination date," Townsend and colleagues report.They calculated that the optimal booster date is 2.7 months prior to a region's highest anticipated prevalence.
They qualify this, however, in the event of a break-through infection, and sought to ascertain optimal time for delaying booster in that event. For individuals who are infected just prior to the next optimal yearly booster vaccination date, they calculated the optimal delay should exceed 9 months. For those experiencing an unlikely, but possible infection just subsequent to receiving a booster on the optimal date, they advise staying on the optimal annual scheduled date.Those with breakthrough infection 6 months after receiving an optimally timed booster vaccination are advised to delay receipt of the next annual booster by several months.
Study co-author Alex Dornburg, PhD, assistant professor of Bioinformatics and Genomics, University of North Carolina at Charlotte, remarked on this aspect of the study, in the released statement.2
"Considering an individual's infection history and adjusting timing based on expected incidence levels isn't something we've done before in vaccination campaigns," Dornburg said. "This tailored approach will have a significant impact on how we manage not only COVID-19, but also other circulating vaccine-targetable diseases."
