Quantitative Estimation of Anti-Spike SARS-CoV-2 IgG Antibody Response After Covishield Vaccination in Healthcare Workers

ABSTRACT

Background: Most studies of COVID vaccination focused on cell-mediated immunity and serum IgG antibodies, overlooking the role of anti-Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) neutralizing IgA antibodies in preventing viral infection. SARS-CoV-2 vaccine generates variable Anti-Spike IgG responses following one or two vaccine doses in almost all individuals for protection. Aim: The study aimed to quantify and estimate the Anti-Spike SARS-CoV-2 IgG antibody response after the second dose of the Covishield vaccine in healthcare workers (HCWs) over the time frame of one, three, and six months. Material and Methods: 30 HCWs who had received both doses of the Covishield vaccine were selected and divided into three groups based on the time elapsed after the second dose of vaccine for serological analysis. Post-vaccination antibody responses were measured using the SARS-CoV-2 IgG Quantitative assay (detection threshold & GE;50 AU/ml) using chemiluminescent microparticle immunoassay (CMIA). Data were analyzed using the Kolmogorov-Smirnov test, Kruskal-Walli's test, and Mann-Whitney U test. Result: Vaccination leads to measurable anti-spike IgG antibodies in HCWs. Only 1 individual was seronegative. The highest antibody titer was reported after one month of the second dose (3615.3 AU/ml). The lowest antibody titer (491.5 AU/ml) was seen after six months of the second dose of Covishield is statistically significant. Conclusion: Anti-Spike SARS-CoV-2 IgG antibody determination is necessary for an immune response after vaccination. This titer decreases with time consequently as the duration after the second dose of the Covishield vaccine increases. This helps assess the requirement of a booster dose for effective immunity against coronavirus.