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

Longitudinal tracing of antibody responses to the ChAdOx1 and the BNT162b2 COVID-19 vaccines in 45,965 adults from the United Kingdom give indications for vaccine prioritization. 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.

Automated summary

A longitudinal study on 45,965 adults in the UK revealed that older individuals, especially those aged >60 years, had lower antibody levels after a single dose of ChAdOx1 or BNT162b2 COVID-19 vaccines. Prioritizing vaccine allocation for those not previously infected and older individuals for the second dose is recommended based on the findings. Further data is needed to fully understand the relationship between quantitative antibody responses and vaccine-mediated protection.