Early Pfizer Covid-19 Vaccine Elicited Spike Antibody (total, IgG, IgM) Responses Compared to Chemiluminescent Neutralizing Antibodies

Responses Compared to Chemiluminescent Neutralizing Antibodies. Abstract Introduction: We compared the total, IgG and IgM spike antibodies (S-Ab) to neutralizing antibody (N-Ab) responses in seronegative subjects after the first and second doses of the BNT162b2 mRNA COVID-19 vaccine. Methods: sixty-five volunteers were tested pre-vaccination, 10 days after the first dose of vaccine, and 20 days after dose two (17 males, 48 females, mean age 41.5 ± 14.1-years). Total/IgG/IgM were assessed with Roche and Abbott immunoassays, with N-Ab using the Snibe Maglumi SARS-CoV-2 immunoassay. Results: Ten days after first vaccination, 64.6% (n = 42) and 66.2% (n = 43) were S-Ab (total and IgG) positive; however, only 13.8% (n = 9) and 10.8% (n = 7) were IgM and N-Ab positive. Younger patients (< 50-years-old) had significantly higher S-Ab responses after the first vaccine dose (difference between age groups: total 1.12 BAU/mL, 95% CI 0-3.69, p = 0.02; IgG 11.4 BAU/mL, 95% CI 2.72-37.1, p = 0.01; IgM COI 0.24, 95% CI 0.05-0.52, p = 0.01). 20 days after second vaccination, ALL participants had high antibodies - IgG (265-7764 BAU/mL), total (274-6127 BAU/mL) and N-Ab (0.51-15.7 ug/mL). In total, females displayed greater IgG (52.5 BAU/mL, 95% CI 2.47-912, p = 0.02) and N-Ab (0.1 ug/mL, 95% CI 0.01-1.26, p = 0.03) responses than males. Total and IgG displayed better correlation with N-Ab after vaccination than IgM (total and IgG Pearson correlation coefficient both r = 0.96, IgM r = 0.78). Conclusion: In seronegative subjects, S-Ab or N-Ab may not be reactive 10 days after a single dose of vaccine, especially males ≥ 50-years-old. However, all subjects had high total, IgG and N-Ab positive 20 days after 2 vaccinations.