Lancet
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In the UK, booster COVID-19 vaccinations have been recommended biannually to people considered immune vulnerable. We investigated, at a population level, whether the absence of detectable anti-SARS-CoV-2 spike protein IgG antibody (anti-S Ab) following three or more vaccinations in immunosuppressed individuals was associated with greater risks of infection and severity of infection. ⋯ UK Research and Innovation, Kidney Research UK, Blood Cancer UK, Vasculitis UK, and Cystic Fibrosis Trust.