ABSTRACT
BackgroundThe magnitude of protection conferred after recovery from COVID-19 or by vaccine administration, and the duration of protective immunity developed, remains ambiguous. MethodsWe investigated the factors associated with antibody decay in 519 individuals who received treatment for COVID-19-related illness or received COVID-19 vaccination with two commercial vaccines, viz., an adenoviral vector-based (AZD1222) and a whole-virion-based inactivated (BBV152) vaccine in Chennai, India from March 2021. Blood samples collected during regular follow-up post-infection/vaccination andwere examined for anti-SARS-CoV-2 IgG by a commercial automated chemiluminescent immunoassay (CLIA). ResultsAge and underlying comorbidities were the two variables that were independently associated with the development of breakthrough infection. Individuals who were >60 years of age with underlying comorbid conditions had a [~]15 times and [~]10 times greater risk for developing a breakthrough infection and hospitalization, respectively. The time elapsed since the first booster dose was associated with attrition in anti-SARS-CoV-2 IgG, where each month passed was associated with an ebb in the neutralizing antibody levels by a coefficient of -6 units. ConclusionsOur findings advocate that the elderly with underlying comorbidities require a second booster dose with AZD1222 and BBV152.
