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Background Two mRNA vaccines, Pfizer-BNT162b2 and Moderna-mRNA-1273, obtained the Emergency Use Listing (EUL) by WHO for preventing COVID-19. However, little is known about the difference in antibody responses induced by these two mRNA vaccines in naïve and previously infected (PI) individuals. Method We investigated the levels of anti-S-RBD (total, IgG, and IgA) levels in naïve and PI individuals, 1–13 (median = 6) weeks following the second dose of either vaccine. Results In the naïve-vaccinated group, the mRNA-1273 vaccine induced significantly higher levels of anti-S-RBD total antibodies (3.5-fold; p < 0.001), IgG (2-fold-p < 0.01), and IgA (2.1-fold, p < 0.001) as compared to the BNT162b2 vaccine. In addition, both vaccines produced significantly higher anti-S-RBD total antibody levels in the PI- group compared to naïve-vaccinated group. The PI group elicited a higher level of anti-S-RBD IgG than the naïve-BNT162b2 (p = 0.05), but not more than the naïve-mRNA-1273 (p = 0.9) group. Interestingly, the PI vaccinated group elicited a comparable level of IgA ratio to the naïve-mRNA-1273 group but significantly higher than the naïve-BNT162b2 group (1.6-fold, p < 0.001). Conclusion Our results showed that the PI vaccinated group produces a higher level of antibodies than the naïve vaccinated group, particularly for those vaccinated with BNT162b2.

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