Analysis of Antibody Responses of Vaccinated Persons with Coronavac

Author(s): Aydin BALCI, Muhammed Emin DÜZ, Sibel Günay

Introduction: Vaccination is the most efficient method available to combat the COVID-19 pandemic. However, vaccine production and logistics problems bring the dose-comparing approach to mind to protect the most people in the shortest time.

Method: Day one (believed to be first dose-dependent), day 14, day 21, and 3 months after 2nd dose anti-SARS-COV-2 anti-spike IgG and IgM responses of one and two doses of CoronaVac (Sinovac Life Sciences, Beijing, China) COVID-19 vaccine in 80 healthcare workers without a history of COVID-19 were investigated.

Result: There was a statistically significant difference between day one (median:7.13) and day 14 (median:10.18) and day 21 (median:11.75) and between day 14 and day 21 in terms of mean IgG values (p<0.0001, p<0.0001, and p=0.005, respectively). Also, a significant correlation was found between day 14 and day 21 in terms of IgM values (r=0.888, p<0.001), and a robust correlation were found between day one and day 14 and between day 14 and day 21 in IgG values (r=0.798, p< 0.001 and r=0.947, p<0.001). Considering the 3rd-month data (IgG median:5.235, and IgM median:0.301), we observed that the antibody levels decreased significantly compared to the 21st and 14th days (p:0.031 for IgG, and p:0.042 for IgM).

Conclusion: Dose-comparing strategy can provide a certain level of protection and slow down the pandemic by delaying viral mutations at least until the second dose of vaccine, especially those living and working in crowded places. T and B cell memory efficiency should be kept in the foreground instead of thinking that individuals with low antibody responses are vulnerable to COVID-19. The long-term protection of the Coronavac vaccine is questionable, and a booster may be required at certain intervals until the pandemic is over.