SARS-CoV-2 IgG Antibody Levels After Inactivated Vaccine (CoronaVac) among Elderly.

We aimed to describe the antibody response against SARS-CoV-2 after inactivated COVID-19 vaccine in elderly individuals. SARS-CoV-2 IgG levels were measured in the blood samples of 126 volunteers over the age of 60. The antibody positivity rate was 42.8% after the first dose and 96.8% after the second dose of the vaccine. The median antibody titers after two vaccine doses were 561.3AU/mL and 43AU/mL, respectively( p <0.001). After vaccination, 22.2% of the participants had antibodies equivalent to 1:80 dilutions in plaque reduction neutralization test (PNRT). We believe that the booster dose is needed to continue the protective immune response in especially elderly groups.