Background and objectives: Pandemics have serious adverse impacts on public health, economy, social structure, and overall growth and development of a nation. Such impacts can be mitigated by timely introduction of effective vaccination programs. This was successfully achieved in India. This study was performed to compare the anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin G (IgG) responses after first and second dose of coronavirus disease 2019 (COVID-19) vaccination. Methods: This cross-sectional study included 60 people who were vaccinated with the AstraZeneca vaccine at Karnataka Institute of Medical Sciences, Hubballi, India. The subjects were divided into two groups. Group I included 30 people who had received a single dose of the vaccine, and group II included 30 people who had received two doses of the vaccine. Exclusion criteria included having a history of influenza like illness/severe acute respiratory infection/proven COVID-19 infection in past 6 months. The antibody response was measured by the Anti-SARS-CoV-2 IgG test using the VITROS Anti-SARS-CoV-2 IgG Reagent Pack. Results: We observed that 97% of the subjects had reactive IgG antibodies after receiving two doses of the vaccine, whereas only 83% of the subjects developed antibodies after a single dose of the vaccine. A positive correlation was observed between the development of reactive antibodies and the duration between the first dose and the second dose (r=0.24). Conclusion: Based on the results, the two-dose vaccination with the AstraZeneca vaccine is beneficial over the single-dose vaccination for protection against COVID-19. Moreover, increasing the duration between doses might improve the antibody response.
