High rates of SARS-CoV-2 reinfection in residents of long term care facilities despite robust spike-specific immunity following serial vaccination.

Older adult residents of long-term care facilities (LTCFs) suffered high rates of mortality during the initial stages of the COVID-19 pandemic but their clinical risk has decreased markedly following vaccination. Here we determined humoral and cellular immunity following delivery of a 5th vaccine dose, an mRNA spike B1:BA.1 bivalent vaccine, to care home residents. The delivery of a 5th vaccine elicited a plateau of spike-specific immunity that remained broadly stable over 100 days in almost all people. Despite this, 15% of residents had a primary infection and 30% became reinfected during 6-months of follow up. These findings reveal that serial vaccine delivery can establish robust systemic spike-specific immune responses in frail older people but that this does not reliably prevent SARS-CoV-2 reinfection. As such, additional approaches should be considered to reduce reinfection risk in this vulnerable population group.