Levin EG, Lustig Y, Cohen C, et al. - An increasing incidence of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been observed in Israel despite high vaccine coverage and effectiveness. This study suggested a substantial reduction in humoral response after 6 months of receiving the second dose of the BNT162b2 vaccine.

• This is a 6-month longitudinal prospective study of vaccinated health care workers who underwent monthly testing for the presence of anti-spike IgG and neutralizing antibodies. A total of 4,868 participants were involved, with inclusion of 3,808 in the linear mixed-model analyses.

• There appeared a reduction in the level of IgG antibodies at a consistent rate, whereas reduction in the neutralizing antibody level occurred rapidly for the first 3 months with a relatively slow decrease thereafter.

• Although there was a high correlation between IgG antibody levels and neutralizing antibody titers, the time since receipt of the second vaccine dose appeared influencing the regression relationship between the IgG and neutralizing antibody levels.

• At 6 months following receipt of the second dose, neutralizing antibody titers lowered substantially especially among men, among persons 65 years of age or older, and among persons with immunosuppression.