Real-world effectiveness and antibody responses of BNT162b2 vaccination in long-term care residents: A retrospective case-control study

OBJECTIVES: Older adults in long-term care (LTC) facilities are at high risk for COVID-19-related morbidity and mortality, yet real-world evidence on vaccine effectiveness and immunogenicity in very old populations remains limited. This study evaluated the effectiveness of BNT162b2 vaccination against SARS-CoV-2 infection and assessed post-vaccination antibody responses among institutionalised older adults, including residents aged ≥95 years. METHODS: A retrospective case-control study was conducted in a geriatric LTC facility in Vienna, Austria. Thirty-eight residents with confirmed SARS-CoV-2 infection were matched to 76 non-infected controls by age, sex, and nutritional risk. Vaccine effectiveness (VE) was estimated using odds ratios (ORs) for infection. Antibody concentrations were analysed in vaccinated residents without prior infection, with adequate response defined as ≥120.1 AU/ml. RESULTS: Vaccination was associated with a significantly reduced risk of infection (OR 0.20; 95% CI: 0.07-0.55), corresponding to a VE of 80%. Among residents aged ≥95 years, VE was 94% (95% CI: 28-99%). Overall, 82.8% of vaccinated residents achieved adequate antibody concentrations, with no significant association between age and antibody levels. Among those aged ≥95 years, 90.9% reached adequate antibody concentrations. CONCLUSIONS: BNT162b2 vaccination provided substantial protection and robust antibody responses among LTC residents, including those of very advanced age, supporting the effectiveness of mRNA vaccination in highly vulnerable institutionalised populations.