Background: SARS-CoV-2 is a highly contagious virus that elicits COVID-19, a respiratory illness with a range of symptoms that can progress systemically and prove fatal. Vaccine development against the virus has been a crucial advance in combatting the pandemic, with vaccine efficacy being evaluated through analysis of antibody response. However, the magnitude of antibody response varies by vaccine and individual immunological status. Although even suboptimal antibody response may provide protection, COVID-19 immunity is a multi-factorial process that includes other immune components.

Objective: To measure changes in IgGSP antibody levels in response to the COVID-19 Sputnik vaccine, as analyzed by three serum samples collected at different time points in both seropositive and seronegative individuals.

Methods: A pre-post interventional study was carried on 324 military HCWs administering the Sputnik Vaccine at the Military Central COVID-19 Vaccination Unit from March till the end of July 2021.

Results: Participants were divided into seropositive and seronegative groups based on SARS-CoV-2 antibody levels. The seropositive group had a greater increase in IgGSP antibody titer after one vaccine dose. Both groups showed a significant decline in IgGSP levels after 12 weeks of complete vaccination, but the decline was less prominent in the seropositive group. This suggests the need for booster doses every six months to strengthen the immune system after the decline.

Conclusion: IgGSP antibodies are effective against SARS-CoV-2, but the minimum level for protection is unclear and requires further research to establish a cut-off point.