Comparative Analysis of IgG Antibody Titers Induced by Three Different SARS-COV-2 Vaccines in Healthy Adults of Pakistan.

Covid-19 is a contagious disease caused by severe acute respiratory syndrome corona virus 2 (SARS-CoV-2). In order to control this disease, different effective vaccines have been developed. This study is an attempt to determine the strength and duration of immunogenicity of various established vaccines. This cross-sectional, observational study was conducted to compare the efficacy of three different vaccines; Pfizer BNT 162b2, Sinovac, and CanSino, respectively, after a duration of 3 months, in the healthy adult population of Pakistan. In this study 371 healthy participants (aged 12-25 years) of both genders (male and females) were enrolled. The blood sample was drawn 90 days after the complete vaccination process. The humoral response (IgG) was analyzed by electrochemiluminescence immunoassay (ECLIA) method with Roche Anti-SARS-CoV-2 S analyzer kit. Descriptive statistical analysis was performed using IBM SPSS statistics version 22 and P < 0.05 was considered significant. The mean antibody titer in Pfizer-group was 12,536.35 U/mL, followed by 5168.68 U/mL in the Sinovac group and 4284.32 U/mL in the CanSino group. The Pfizer-group showed gender-specific significant differences, with higher antibody levels in males (P = 0.006) as compared to Sinovac and Cansino groups. The Mean IgG antibody levels of the Pfizer-vaccinated group were significantly higher than the Sinovac-vaccinated group and the CanSino-vaccinated group (P = 0.000, each). However, the mean difference between the Sinovac-vaccinated group and the CanSino-vaccinated group was not significant. Vaccine-induced seropositivity was found in the whole cohort. The mRNA-based vaccine produced the highest immune response, and thus, it is recommended for future application.