Humoral response is enhanced after ipsilateral double intramuscular injection of BNT162b2 COVID-19 vaccine

Abstract

Background: Although the utility of vaccines in combating coronavirus disease 2019 (COVID-19) cannot be overstated, the intensity and duration of immune response play a key role in maintaining their efficacy. This retrospective observational study therefore investigated whether ipsilateral or contralateral injection of two doses of vaccine can elicit a different humoral response.