A new study out Wednesday found that two doses of Pfizer and AstraZeneca's COVID-19 vaccines offer strong protection against the Delta variant, almost as much as the previously dominant Alpha strain.
Based on real world data, the New England Journal of Medicine study confirms Public Health England's earlier findings about the efficacy of Pfizer and AstraZeneca's vaccines.
Wednesday's study found that two doses of Pfizer's shot were about 88% effective at preventing symptomatic disease from the Delta variant, compared to 93.7% against the Alpha variant.
Meanwhile, two shots of the AstraZeneca vaccine were 67% effective against Delta, and 74.5% effective against Alpha.
Data from Israel, which has one of the highest vaccination rates in the world, had estimated Pfizer's effectiveness against symptomatic disease to be even lower, but suggests protection against severe disease remains high.
Officials say vaccines are highly effective against Delta, now the dominant variant worldwide, but the study reiterates that just one dose of the vaccines is not enough for high protection.
Public Health England had previously said that a first dose of either vaccine was around 33% effective against symptomatic disease from the Delta variant.
Wednesday's study found that one dose of Pfizer's shot was 36% effective, while one dose of AstraZeneca was around 30% effective.