The latest on the Covid-19 pandemic as Olympics approach
Researchers in Britain reported Tuesday they had found more evidence that two doses of Pfizer’s and AstraZeneca’s coronavirus vaccines protect people well against the Delta variant of coronavirus.
But a single dose of either vaccine provides very little protection against Delta, also known as B.1.617.2, the researchers reported in the New England Journal of Medicine.
The team looked at overall vaccine efficacy in England first when the Alpha variant, known also as B.1.1.7, was the predominate variant, and then when Delta took over.
The vaccines being given in England are Pfizer’s two-dose vaccine and AstraZeneca’s two-dose vaccine.
“Effectiveness after one dose of vaccine was notably lower among persons with the Delta variant than among those with the Alpha variant; the results were similar for both vaccines,” Dr. Jamie Lopez Bernat of Public Health England and colleagues wrote. Against Delta, a single dose of either vaccine was only about 30% effective, they found.