An analysis by Public Health England (PHE) suggests that two doses of COVID-19 vaccines from Pfizer/BioNTech and AstraZeneca are "highly effective" against the B.1.617.2 coronavirus variant first identified in India, the UK government announced on Saturday. Mary Ramsay, head of immunisation at PHE, said the data "provides reassurance that two doses of either vaccine offer high levels of protection against symptomatic disease from the B.1.617.2 variant," adding that "we expect the vaccines to be even more effective at preventing hospitalisation and death."
The study included 12,675 genome-sequenced cases of COVID-19 in England, with 1054 of these cases confirmed as having the B.1.617.2 variant. The analysis included data for all age groups from April 5 to cover the period since the B.1.617.2 variant emerged.
The study found that from April 5 to May 16, Pfizer/BioNTech's COVID-19 vaccine Comirnaty, also known as BNT162b2, was 87.9% effective against symptomatic disease from the B.1.617.2 variant two weeks after the second dose, compared with 93.4% effectiveness against the B.1.1.7 variant, which was first identified in Kent and is the dominant strain in the UK. Meanwhile two doses of AstraZeneca's Vaxzevria, formerly known as AZD1222, were 59.8% effective against the B.1.617.2 variant and 66.1% effective against the B.1.1.7 variant.
"The difference in effectiveness between the vaccines after two doses may be explained by the fact that rollout of second doses of AstraZeneca was later than for the Pfizer/BioNTech vaccine, and other data on antibody profiles show it takes longer to reach maximum effectiveness with the AstraZeneca vaccine," PHE explained.
Results also showed that both vaccines were 33.5% effective against symptomatic disease from B.1.617.2 three weeks after the first dose, compared with 51.1% effectiveness against the B.1.1.7 variant. PHE indicated that it will continue to evaluate the effectiveness of the vaccines on severe outcomes "over the coming weeks."
Jamie Lopez Bernal, lead author of the study, noted that there was more confidence in the data from the first vaccine dose compared with that from the second. "There are bigger numbers that have been vaccinated with one dose. So I think we classify that as moderate certainty around the first dose, but low levels of confidence around the second dose," he said.
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