Assessment of Post-Vaccination Immunologic Responses in Inactivated Virus COVID-19 Respondents

Introduction: The Indonesian Government's plan to contain the COVID-19 pandemic, aside from implementing health protocols, also involves vaccinating everyone with the inactivated SARS CoV2 vaccine until herd immunity is reached. The aim of this study was to assess the post-vaccination immune response to inactivated SARS CoV2 vaccine, namely Sinovac/Sinopharm, by measuring the antibodies (IgM and IgG) in subjects after their second dose of vaccination. Materials and Methods: The design of the study was a cohort study using simple random sampling with 51 respondents aged 18-56 years who had received two doses of inactivated SARS-CoV-2 vaccine. All respondents were screened for SARS-CoV-2 infection prior to inclusion. Serum IgM and IgG antibodies were detected using a specific and sensitive automated chemiluminescent immunoassay (CLIA). CLIA uses the Cut Off Point (COI) value of >1 AU/ml for IgM and the Reactive Value of >10 AU/ml for IgG. Results: This study showed that the IgM levels using a reactive Cut Off Point (COI) >1 were 18% in the first month, 14% in the third month, and 10% in the sixth month. There was a constant decline in the third comparison. Meanwhile, compared to the first month, 59% of respondents had IgG levels with reactive values over 10 AU/ml, which after decreasing by 35% in the third month, the number increased by 47% in the sixth month. Conclusion: It has been evident that IgG and IgM antibody response could be induced by inactivated SARS-CoV-2 vaccine which can be influenced by age and detection time after the second dose of vaccination. Boosters, however, must be given after six months of the second dose, since antibody levels were seen to decrease after this period.