Comparative immunogenicity and safety of Gam-COVID-Vac and Sinopharm BBIBP-CorV vaccines: results of a pilot clinical study

Introduction: There are few comparative studies on efficiency of broad range COVID19 vaccination strategy. This pilot aims to describe the effect of mixed COVID19 vaccination on vaccination adoption and subsequent total immunity, Conducted in Republic of Belarus, this pilot clinical study shows varying immunogenic responses to Sputnik V (Gam-COVID-Vac), Russian Federation (RF) and Sinopharm (BBIBP-CorV), People's Republic of China (PRC) vaccines.Objective: To compare the immunogenicity and reactogenicity of Sputnik V (Gam-COVID-Vac) and Sinopharm (BBIBP-CorV) vaccines in vaccinated individuals. Materials and MethodsA total of 60 adults participated in the present study. The immune response after vaccination was assessed using enzyme immunoassay. IgG levels were measured in all participants at three time points: before vaccination, on the 42nd day after the first vaccine dose, and in 6 months after the first vaccine dose. Age, sex of participants, vaccine type, history of COVID-19/IgG seropositivity were included in the multivariate analysis. The results of the SARS-CoV-2 infection antibody test were quantified according to the WHO First International Standard (NIBSC code:20/136) and measured in international units (BAU/ml).Results: The study participants (n = 60) were divided into two groups where 50 % (n = 30) were vaccinated with Sputnik V (Gam-COVID-Vac), and 50 % (n = 30) were vaccinated with Sino-pharm (BBIBP-CorV). Women represented 63 % and 77 % of Sputnik V and Sinopharm groups, respectively. The IgG levels on day 42 after the first vaccine dose were: Sputnik V (Gam-COVID-Vac): Me = 650.4 (642.2-669.4); Sinopharm (BBIBP-CorV: Me = 376.5 (290.9-526.4) (UMann--Whitney = 164, p = 0.000024). The IgG levels in 6 months after the first vaccine dose were: Sputnik V (Gam-COVID-Vac)Me = 608.7 (574.6-647.1); Sinopharm (BBIBP-CorV) Me = 106.3 (78.21-332.4); (UMann-Whitney = 172.5, p-value = 0.000042)). In a multivariate model Sputnik V vaccine type and IgG seropositivity at the baseline were significantly associated with higher levels of IgG both at 42 days and 6 months post-vaccination. Reactions after vaccination appeared in 27 vaccinated people (45 %).Conclusion: This pilot study demonstrated that Sputnik V (Gam-COVID-Vac) vaccine was more immunogenic than Sinopharm (BBIBP-CorV) vaccine. IgG levels in vaccinated individuals who previously recovered from SARS-CoV-2 infection (hybrid immunity) were higher than in SARS-CoV-2 infection immunenaive people. Reactions after vaccines administration were mild to moderate.