Immunogenicity trends 1 and 3 months after second BNT162B2 vaccination among healthcare workers in Israel

We evaluated the antibody response to the BNT162B2 vaccine among healthcare workers (HCWs) to identify factors associated with decreased immunogenicity.

This prospective cohort study included consenting HCWs who completed a questionnaire regarding background illnesses, medications, and post-vaccination allergic reactions or rash. All HCWs were tested for anti-spike antibodies (LIAISON SARS-CoV-2 S1/S2 IgG assay) 1 and 3 months after the second vaccine dose. A multivariate mixed linear model was adjusted to participants' data and fit to predict antibody levels after the second BNT162B2 vaccine dose, based on antibody levels at 1 month and the slope between 3 months and 1 month. Multivariate analyses identified factors associated with lower antibody levels.

In total 1506 HCWs were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. Older age was associated with lower mean antibody levels (-1.22 AU/mL, p < 0.001, 95%CI -1.43 to -1.01). In addition, male sex (-22.16 AU/mL, p < 0.001, 95%CI -27.93 to -16.39), underlying condition (-10.86 AU/mL, p 0.007, 95%CI -18.81 to -2.91) and immunosuppressive treatment (-28.57 AU/mL, p 0.002, 95%CI -46.85 to -10.29) were associated with significantly lower mean antibody levels. Allergic reactions after vaccine administration or peri-vaccination glucocorticosteroid treatment were not correlated with antibody levels.

Most HCWs had measurable antibodies at 3 months. Risk factors for lower antibody levels were older age, male sex, underlying condition, and immunosuppressive treatment. These factors may be considered when planning booster doses during vaccine shortages.