Successful phase 3 trial outcomes have been reported for numerous vaccines that induce robust humoral and cellular immune responses against the SARS-CoV-2 spike protein.1–6 To gain rapid control of accelerating cases and maximise public health impact, the UK Government has adopted the strategy of delaying second vaccination to 12 weeks. 21 (29%) participants had evidence of previous SARS-CoV-2 infection: 16 with positive baseline serology, and five further with strong T-cell responses to non-spike antigens post-vaccination (>100 spot forming units SFU per 106 peripheral blood mononuclear cells PBMC). ...those with serological evidence of previous disease at baseline mount robust antibody and T-cell responses after a single dose of vaccine.