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LONDON, March 26 (Reuters) - One dose of Pfizer
COVID-19 vaccine offers an immune response similar to that
generated by infection and could also offer protection from
variants to people who have previously had the virus, a British
study said on Friday.
Britain in December opted to extend the gap between doses in
its vaccine rollout to up to 12 weeks, with officials saying
they were confident in their analysis that initial doses of
Pfizer and AstraZeneca vaccines generated some
protection.
The study, led by Sheffield and Oxford Universities with
support from the UK Coronavirus Immunology Consortium, and
released as a pre-print on Friday, found 99% of people generate
strong immune responses after one dose of the Pfizer-Biontech
vaccine.
It backs up real-world data on Britain's vaccine rollout
from a study called SIREN which has found that one shot of
either vaccine reduces severe disease.
"SIREN is actually showing very high vaccine effectiveness
against hospitalisation after a single dose, with the majority
of these people having not had infection before. So what we're
trying to do is look at the mechanisms for that," Susanna
Dunachie of the University of Oxford's Nuffield Department of
Medicine, told reporters.
"We are seeing T-cell and antibody responses after one dose
in people who have not had infection before. So we find that
quite reassuring."
The study is the largest real world study on T-cell and
antibody responses from Britain's vaccine rollout, and looked at
healthcare workers, mainly women, who were given one dose of the
Pfizer shot.
The researchers analysed blood samples from 237 people, and
found that the antibody and T-cell responses in those who had
not previously had COVID-19 resembled those generated by natural
infection.
Those who had been previously infected generated a stronger
and broader immune response, with a T-cell response that was
around six times higher than those who had not been infected.
Thushan de Silva, study author from the University of
Sheffield, also said that boosting pre-existing antibody
responses could provide protection against coronavirus variants,
including the one first discovered in South Africa which has
been shown to reduce the efficacy of existing vaccines.
(Reporting by Alistair Smout. Editing by Jane Merriman)
