Comparison of Covid-19 IgG Anti-Spike Antibody Titer after Vaccination with Sputnik V in Seropositive and Naïve Vaccinees

Introduction: Immunity to SARS-CoV-2 has shown to reduce the risk of having a severe infection and initiate a good degree of disease protection. Studies assessing the antibody titer after vaccination can be very helpful to see whether previously infected individuals have better immunological response as compared to uninfected or antibody naïve individuals. Aims & Objectives: Comparison of Anti-spike IgG antibody among vaccinees with or without previous exposure to COVID-19. To determine whether single dose regimen can produce significant antibody titer amongst previously infected cases and design vaccine dosage regimens accordingly. Place and duration of study: This study was conducted at Chughtai Institute of Pathology from April 2021 to June 2021. Material & Methods: Blood samples were collected from 83 adult male and female vaccinees at baseline, 3 weeks after the first dose and finally 7 days after the second dose. Previously infected individuals’ record was noted separately. Samples were immediately analyzed using Abbott SARS-CoV-2 IgG II quant two step immunoassay. Data was analyzed using SPSS 23.0. A p-value of <0.05 was considered significant.Results: Majority of the candidates (57 %) were females and on analysis it was found that 42% of the patients were seropositive whereas 58% of the patients were antibody naïve before receiving the first dose of vaccine. There was a significant difference between mean antibody titer of seropositive and seronegative study participants at day 0, day 21 and finally on day 28 (p value <0.001) with seropositive individuals having higher antibody titers even after first vaccine shot. Conclusion: Post vaccination immunological response was higher in seropositive individuals as compared to the antibody naïve and this finding can help the policy makers to design a single dose vaccine regimen for the former category.