Quantitative neutralizing antibody using chemiluminescence assay for evaluating antibody response following inoculation of inactivated vaccine among healthcare workers in Surabaya, Indonesia

The primary objective of this study is to assess the quantifiable neutralizing antibody (NAb) levels and the concentration of immunoglobulin G against the spike receptor-binding domain (sRBD IgG) of the SARS-CoV-2 virus post-vaccination. This observational research was carried out within the premises of Dr. Soetomo Hospital, situated in Surabaya, Indonesia, and targeted healthcare professionals. A cohort of 50 healthcare workers was selected for participation. Blood specimens were gathered on five separate occasions from each participant. The initial sample was procured before the initial dose of the CoronaVac inactivated vaccine was administered, while the subsequent samples were taken at intervals of 14, 28, 90, and 180 days after the second dose. Quantitative evaluations of NAb and sRBD IgG levels were executed employing a chemiluminescent immunoassay using the Autobio AutoLumo A1000 analyser. The zenith of both NAb and sRBD IgG levels occurred at the 14-day mark, subsequently displaying a decline after 28 days post the second vaccine administration. The concordance between sRBD IgG and NAb levels exhibited a moderate correlation (kappa = 0.600). No statistically noteworthy disparity was detected in sRBD IgG and NAb levels by the 90th day of observation or before participants encountered instances of COVID-19 infection. The peak concentrations of NAb and sRBD IgG were attained at the 14-day milestone yet experienced a descent commencing 28 days after the second inactivated vaccine dose administration.