Comparison of the Immune Responses to COVID-19 Vaccines in Bangladeshi Population

Background: The adaptive immune response is a crucial component of the protective immunity against SARS-CoV-2, generated after infection or vaccination. Methods: We studied antibody titers, neutralizing antibodies and cellular immune responses to four different COVID-19 vaccines, namely Pfizer-BioNTech, Moderna Spikevax, AstraZeneca and Sinopharm vaccines in the Bangladeshi population (n = 1780). Results: mRNA vaccines Moderna (14,655 +/- 11.3) and Pfizer (13,772 +/- 11.5) elicited significantly higher anti-Spike (S) antibody titers compared to the Adenovector vaccine AstraZeneca (2443 +/- 12.8) and inactivated vaccine Sinopharm (1150 +/- 11.2). SARS-CoV-2-specific neutralizing antibodies as well as IFN-gamma-secreting lymphocytes were more abundant in Pfizer and Moderna vaccine recipients compared to AstraZeneca and Sinopharm vaccine recipients. Participants previously infected with SARS-CoV-2 exhibited higher post-vaccine immune responses (S-specific and neutralizing antibodies, IFN-gamma-secreting cells) compared to uninfected participants. Memory B (B-MEM), total CD8(+)T, CD4(+) central memory (CD4(CM)(+)) and T-regulatory (T-REG) cells were more numerous in AstraZeneca vaccine recipients compared to other vaccine recipients. Plasmablasts, B-regulatory (B-REG) and CD4(+) effector (CD4(EFF)(+)) cells were more numerous in mRNA vaccine recipients. Conclusions: mRNA vaccines generated a higher antibody response, while a differential cellular response was observed for different vaccine types, suggesting that both cellular and humoral responses are important in immune monitoring of different types of vaccines.