Diversity in antibody titer at an average of 87 days after the second dose of BNT162b2 mRNA coronavirus disease 2019 vaccine: data from a predominantly elderly population in a practice in Tokyo
It is very important for the elderly, who tend to have serious COVID-19 infection and high mortality rates, to maintain sufficient immunity. We reviewed the medical charts of predominantly elderly population to obtain the data on serum anti-SARS-CoV-2S antibody titer after complete vaccination with the BNT162b2 mRNA vaccine (two doses) and evaluated the background factors associated with the titer. We enrolled 230 participants (101 men and 129 women). Their average age was 71.9 (SD 12.5) years, and median was 72 years. The anti-SARS-CoV-2S antibody titer varied from 0.55 U/mL to 4920 U/mL. We found that the value of the titer varied widely. The value of the titer was negatively associated with age, alcohol consumption, time elapsed from second vaccine dose, and use of immunosuppressive medication. The result that the titer was negatively associated with aging suggests that the timing of additional shot should be carefully determined especially among elderly population.