Immune Responses and Breakthrough Infections After COVID-19 Vaccination

Coronavirus diseases 2019 (COVID-19) vaccines have demonstrated high efficacy and effectiveness in preventing SARS-CoV-2 infection and reducing the risk of emergency room visits, hospitalizations, intensive care unit admissions, and deaths due to symptomatic COVID-19, especially severe and critical COVID-19.1 However, concerns have been raised about the occurrence of breakthrough infections mainly due to the waning of protection over time after vaccination and the appearance of viral variants. To address the waning immunity after vaccination, booster dose of COVID-19 vaccines was introduced. A BNT162b2 booster after either the ChAdOx1 or BNT162b2 primary series substantially increased protection, but that protection waned over time as well.2 Differences in immune response and effectiveness between ChAdOx1 and BNT162b2 based vaccination programs have not yet been consistently observed. © 2023 The Korean Academy of Medical Sciences.