Factors associated with the decay of anti-SARS-CoV-2 neutralizing antibodies among recipients of an adenoviral vector-based AZD1222 and a whole-virion inactivated (BBV152) vaccine in Chennai, India: a cross-sectional cohort study (preprint)

ABSTRACT

Background: The SARS-CoV-2 has caused high rates of morbidity and mortality and is spreading globally, including in populations with high rates of vaccination. The magnitude of protection conferred after recovery from natural infection or by vaccine administration, and the duration of protective immunity developed post-vaccination, remains ambiguous. Methods: We 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 at the State Public Health Laboratory, and the Government Corona Hospital, Chennai, India from March 2021. Blood samples were collected during regular follow-up post-infection/vaccination and tested for their levels of anti-SARS-CoV-2 IgG. Blood collected were tested for their levels of anti-SARS-CoV-2 IgG by a commercial automated chemiluminescent immunoassay (CLIA). Findings: Age 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. Participants who were >60 years of age had an accelerated IgG decay rate, where each day of lapse was associated with a decrease by 23 units. Each month of lapse was associated with an increased risk of contracting a breakthrough infection and hospitalization by 0.85 and 0.85, respectively. Interpretation: Our findings advocate that the elderly with underlying comorbidities represent a high-risk group warranting more medical attention, and measures to boost anti-SARS-CoV-2 immune responses such as administering a second booster dose with both the vaccines, viz., AZD1222 and BBV152 are urgently warranted.