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LONDON, July 21 (Reuters) - Two doses of Pfizer or
AstraZeneca's COVID-19 vaccine are nearly as effective
against the highly transmissible Delta coronavirus variant as
they are against the previously dominant Alpha variant, a study
published on Wednesday showed.
Officials say vaccines are highly effective against the
Delta variant, now the dominant variant worldwide, though the
study reiterated that one shot of the vaccines is not enough for
high protection.
The study, published in the New England Journal of Medicine,
confirms headline findings given by Public Health England in May
about the efficacy of COVID-19 vaccines made by Pfizer-BioNTech
and Oxford-AstraZeneca, based on real-world
data.
Wednesday's study found that two doses of Pfizer's shot was
88% effective at preventing symptomatic disease from the Delta
variant, compared to 93.7% against the Alpha variant, broadly
the same as previously reported.
Two shots of AstraZeneca vaccine were 67% effective against
the Delta variant, up from 60% originally reported, and 74.5%
effective against the Alpha variant, compared to an original
estimate of 66% effectiveness.
"Only modest differences in vaccine effectiveness were noted
with the Delta variant as compared with the Alpha variant after
the receipt of two vaccine doses," Public Health England
researchers wrote in the study.
Data from Israel has estimated lower effectiveness of
Pfizer's shot against symptomatic disease, although protection
against severe disease remains high.
PHE had previously said that a first dose of either vaccine
was around 33% effective against symptomatic disease from the
Delta variant.
The full study published on Wednesday found that one dose of
Pfizer's shot was 36% effective, and one dose of AstraZeneca's
vaccine was around 30% effective.
"Our finding of reduced effectiveness after the first dose
would support efforts to maximise vaccine uptake with two doses
among vulnerable groups in the context of circulation of the
Delta variant," the authors of the study said.
(Reporting by Alistair Smout; editing by Barbara Lewis)
