Abstract
[Background] Several vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are in use worldwide. However, their efficacy and safety in the elderly have not been fully assessed.
[Methods] The SARS-CoV-2 IgG II Quant assay (Abbott Diagnostics;positive threshold 50 AU/mL) was used to measure the IgG antibod- ies against SARS-CoV-2 of 185 participants (79 nursing home residents or inpatients of long- term care units 60 years or older, 62 outpa- tients 60 years or older, and 44 medical staff younger than 60 years). Measurement was done before their first and second vaccinations and one month after the second vaccination. [Results] After the first vaccination, only half of the nursing home residents or inpatients became positive for IgG, while 80% of the outpatients and 100% of the medical staff became positive. After being fully vaccinated, 90% of the nursing home residents or inpatients became positive for IgG, as did 100% of the outpatients and medical staff. However, the median IgG level one month after the second vaccination in the nursing home residents or npatients was only 16% and that of the outpatients was only 38% that of the medical staff.
[Conclusions] Vaccines against SARS-CoV-2 are less effective in the elderly;the continua- tion of infection prevention is necessary even after vaccination.
