Antibody responses to SARS-CoV-2 vaccines in 45,965 adults from the general population of the United Kingdom

Wei, Jia; Stoesser, Nicole; Matthews, Philippa C.; Ayoubkhani, Daniel; Studley, Ruth; Bell, Iain; Bell, John I.; Newton, John N.; Farrar, Jeremy; Diamond, Ian; Rourke, Emma; Howarth, Alison; Marsden, Brian D.; Hoosdally, Sarah; Jones, E. Yvonne; Stuart, David I.; Crook, Derrick W.; Peto, Tim E. A.; Pouwels, Koen B.; Eyre, David W.; Walker, A. Sarah

We report that in a cohort of 45,965 adults, who were receiving either the ChAdOx1 or the BNT162b2 SARS-CoV-2 vaccines, in those who had no prior infection with SARS-CoV-2, seroconversion rates and quantitative antibody levels after a single dose were lower in older individuals, especially in those aged >60 years. Two vaccine doses achieved high responses across all ages. Antibody levels increased more slowly and to lower levels with a single dose of ChAdOx1 compared with a single dose of BNT162b2, but waned following a single dose of BNT162b2 in older individuals. In descriptive latent class models, we identified four responder subgroups, including a ‘low responder’ group that more commonly consisted of people aged >75 years, males and individuals with long-term health conditions. Given our findings, we propose that available vaccines should be prioritized for those not previously infected and that second doses should be prioritized for individuals aged >60 years. Further data are needed to better understand the extent to which quantitative antibody responses are associated with vaccine-mediated protection.