The impact of SARS-CoV-2 vaccines on antibody responses in the general population in the United Kingdom
Analysis of data from the UK Covid-19 Infection Survey (n=45,695) found that in those without prior Covid-19 infection, antibody responses to a single dose of the AstraZeneca or Pfizer vaccine were lower in older people, especially those aged over 60 years.
Source:
Oxford University
SPS commentary:
This study compared how antibody concentrations changed after a single dose of either the AstraZeneca or Pfizer vaccine, or after two doses of the Pfizer vaccine (generally given 21-42 days apart), among 45,965 people in the survey. Two doses of the Pfizer vaccine were associated with higher antibody responses across all ages, particularly increasing seroconversion in older people, to similar levels to those achieved followed by a single dose in those with prior infection. The authors suggest that where supplies are limited, vaccines should be prioritised for those not previously infected, and second doses to individuals >60y.
Antibody levels rose more slowly and to lower levels following a single dose of the Oxford-AstraZeneca vaccine than with the Pfizer vaccine, but waned following a single Pfizer dose. However, a linked study reported that one dose of the AstraZeneca or Pfizer Covid-19 vaccines reduced the odds of a new Covid-19 infection by 65% (95% CI 60-70%; p<0.001), with no evidence that benefits varied between the two vaccines.
An investigator for the UK Covid-19 Infection Survey commented: “We don’t yet know exactly how much of an antibody response, and for how long, is needed to protect people against getting covid-19 in the long term—but over the next year information from the survey should help us to answer these questions.”