A Third Dose of mRNA COVID-19 Vaccine Significantly Enhances Anti–SARS-CoV-2 Spike IgG Response in Nursing Home Residents in Italy

A rapid development of effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and their deployment has proved to be a highly successful strategy to reduce the impact of the COVID-19 pandemic.1 Several studies have suggested a waning of humoral responses after primary vaccination.2–4 A third dose of the mRNA vaccine was shown to increase neutralizing antibody levels and prevent severe outcomes.5,6 However, data on the response to third dose of SARS-CoV-2 vaccine in the frail and complex population in Nursing Homes (NHs) are still limited.