LONDON (Reuters) – People in England who have received two doses of Pfizer’s (NYSE:PFE) COVID-19 vaccine produce strong antibody responses as the shot is rolled out, researchers said on Thursday, adding that confidence in vaccines is high.
A study from Imperial College London showed that 87.9% of people over 80 tested positive for antibodies after two doses of Pfizer-BioNTech’s vaccine, compared with 95.5% of those under 60 and 100% of those under 30.
“Although there is some drop-off in positivity with age, in all age groups we get a very good response to two doses of the vaccine,” Paul Elliott, chair of epidemiology and public health medicine at Imperial College London, told reporters.
Antibody levels are only part of the immunity picture, as the vaccines also produce strong T-cell protection.
Nearly 95% of those younger than 30 tested positive for antibodies 21 days after a dose, but that figure dropped in older groups.
However, the U.K. Joint Committee on Vaccination and Immunization (JCVI) has previously found high protection from Pfizer’s vaccine after one dose, even when antibody levels are lower.
The U.K. has extended the interval between vaccine doses to 12 weeks, although Pfizer has pointed out that there are only clinical efficacy data at a three-week interval between vaccinations.
More than 154,000 participants took part in the Imperial Home Surveillance Study for COVID-19 antibodies between Jan. 26 and Feb. 8, which monitors antibody levels in natural infections as well as in vaccinated individuals.
The survey also examined confidence in vaccines and showed it to be high, with 92% having accepted or planning to accept an offer of vaccination, although confidence was lower among blacks, dropping to 72.5%.