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By Alistair Smout
LONDON, June 28 (Reuters) - A mixed schedule of vaccines
where a shot of Pfizer's COVID-19 vaccine is given four
weeks after a AstraZeneca shot will produce better
immune responses than giving another dose of the AstraZeneca
shot, an Oxford study said on Monday.
The study, called Com-COV, compared mixed two-dose schedules
of Pfizer and AstraZeneca vaccines, and found that in any
combination, they produced high concentrations of antibodies
against the coronavirus spike protein.
The data provides support for the decision of some European
countries that have started offering alternatives to AstraZeneca
as a second shot after the vaccine was linked to rare blood
clots.
Matthew Snape, the Oxford professor behind the trial, said
that the findings could be used to give flexibility to vaccine
rollouts, but was not large enough to recommend a broader shift
away from clinically approved schedules on its own.
"It's certainly encouraging that these antibody and T-cell
responses look good with the mixed schedules, but I think your
default has to stay, unless there's a very good reason
otherwise, to what is proven to work," he told reporters.
The highest antibody response was seen in people receiving
two doses of Pfizer vaccine, with both mixed schedules producing
better responses than two doses of AstraZeneca vaccine.
An AstraZeneca shot followed by Pfizer produced the best
T-cell responses, and also a higher antibody response than
Pfizer followed by AstraZeneca.
The results were for combinations of vaccines given at four
week intervals to 830 participants.
(Reporting by Alistair Smout; editing by Michael Holden/Guy
Faulconbridge)
