Robust sars‐cov‐2 antibody responses in asian covid‐naïve subjects 180 days after two doses of bnt162b2 mrna covid‐19 vaccine

Abstract

Background: Subjects with previous COVID‐19 have augmented post‐vaccination re-sponses. However, the antibody response in COVID‐naïve subjects from Southeast Asia is not well known. Methods: 77 COVID‐naïve vaccinees were tested with a full antibody panel [spike antibodies (total (T‐Ab), IgG, IgM) and neutralizing antibodies (N‐Ab)] pre‐vaccination, 10 days after dose 1, and 20/40/60/90/120/150/180 days after dose 2. Results: 10 days after dose 1, 67.6% (48/71)/69.0% (49/71) were T‐Ab/IgG positive; only 15.5% (11/71)/14.1% (10/71) were N‐Ab/IgM positive. While all (100%) subjects had brisk T‐Ab, IgG and N‐Ab antibody responses 20 days after complete vaccina-tion, only 79.1% (53/67) were IgM positive. At 180 days (n = 8), T‐Ab/IgG/N‐Ab were still reactive (lowest T‐Ab 186 U/mL, IgG 617 AU/mL, N‐Ab 0.39 μg/mL), but IgM was negative in all samples. Spike antibody thresholds of T‐Ab 74.1 U/mL (r = 0.95) and IgG 916 AU/mL (r = 0.95) corresponded to N‐Ab reactivity (>0.3 μg/mL). Non‐linear regression analysis showed that N‐Ab would decrease to 0.3 μg/mL by 241 days, whereas T‐Ab/IgG would need 470/163 days to reach titers of T‐Ab/IgG associated with a N‐Ab 0.3 μg/mL (76.4 U/mL and 916 AU/mL respectively). Conclusions: The antibody responses of T‐Ab, IgG and N‐Ab remain high and durable even at 180 days. N‐Ab titers are expected to remain reactive up to 241 days post‐vaccination.