Severe Acute Respiratory Syndrome Coronavirus 2 Infection History and Antibody Response to 3 Coronavirus Disease 2019 Messenger RNA Vaccine Doses.

This article focuses on the kinetics of antibody responses to messenger RNA (mRNA) COVID-19 vaccines among frontline workers with varying histories of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The study found that antibody levels waned over time after the second vaccine dose regardless of prior infection, but individuals with previous infection maintained higher antibody levels longer than those vaccinated only. A third mRNA vaccine dose significantly boosted antibody levels in participants without recent infection, including those with prior infection or breakthrough infection occurring more than 90 days before the booster; however, individuals infected within 90 days before the third dose showed no significant antibody increase post-booster. These findings suggest that timing of booster doses relative to infection history may influence humoral immune responses and support waiting at least three months post-infection to maximize booster effectiveness.