2022 Volume 49 Issue 4 Pages 462-469
Objective: We measured the antibody levels in our staff members over time after coronavirus disease 2019 (COVID-19) vaccination and examined changes in antibody levels after administration of the booster vaccination. We also examined the incidence of adverse reactions after three doses of the vaccine.
Methods: The subjects were 137 employees of our corporation who received two doses of COVID-19 vaccine by Pfizer-BioNTech or Moderna between May and July 2021 and who were subsequently administered COVID-19 antibody testing over time. The antibody levels were measured by quantification of spike protein-specific IgG antibodies and were measured three times in total. The changes in the antibody levels were investigated in two groups who received an additional vaccine dose before the third antibody measurement or not. The incidence rates of adverse reactions were also evaluated.
Results: In case who did not receive the additional vaccine dose, the mean antibody level decreased by 92% at 180 days after the first measurement was performed. On the other hand, in case who received the additional vaccine dose, the antibody level after the additional vaccine dose was 39-fold higher than that in those who were not vaccinated at the same time.
Incidence of all adverse reactions was higher at the second and third measurements than at the first measurement.
Conclusions: These results demonstrated that the antibody level declined considerably with time after vaccination. However, its levels increased sufficiently again after the additional doses. We emphasize that the additional vaccine doses are significant for preventing COVID-19 infection.
