Antibody Response After First and Second BNT162b2 Vaccination to Predict the Need for Subsequent Injections in Nursing Home Residents

Objectives: A massive immunization program was initiated in France in older adults. The aim of the study was to assess the antibody response following BNT162b2 vaccination in nursing home (NH) residents. Methods: Three hundred and sixty-nine NH residents who received two vaccine doses were tested for antibody vaccine response three weeks after the first dose and six weeks after the second dose. We assessed IgG level against SARS-CoV-2 Receptor-Binding Domain (RBD-IgG) and nucleoprotein-IgG (SARS-CoV-2 IgG II Quant and SARS-CoV-2 IgG Alinity assays, Abbott Diagnostics). Results: In NH residents with prior SARS-CoV-2 infection, high RBD-IgG levels (≥ 4,160 AU/mL) were observed after the first dose in 99/129 (76.9%), with no additional antibody gain after the second dose in 74 (74.7%). However, a low RDB-IgG level (