Gokhan Tut, Tara Lancaster, Panagiota Sylla, David Bone, Christopher Bentley, Azar Jadir, Rachel Bruton, Katie Spencer, Soumyajit Mallick, Ahmed Elzaidi, Alexander Dowell, Mary Wu, Ruth Harvey, Edward Carr, Rupert Beale, Maria Krutikov, Oliver Stirrup, Borscha Azmi, Andrew Hayward, Andrew Copas, Laura Shallcross, Paul Moss, Crick COVID Immunity Pipeline
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.