British researchers found two doses of either the Pfizer-BioNTech vaccine or the AstraZeneca one were only slightly less effective at blocking symptomatic illness from the COVID-19 delta variant than from earlier mutations – and importantly, remain hugely protective at preventing hospitalization.
But there’s an important catch: Just one dose proved far less effective against the delta variant than against earlier versions of the virus. That has prompted Britain, which originally extended the gap between doses, to speed up second shots.
Experts say the Moderna vaccine, the same type as Pfizer’s, should be similarly protective.
Johnson & Johnson is still studying how its one-dose vaccine fares against the variant. The company notes its shot does protect against a different worrisome mutant – the so-called beta variant that emerged in South Africa and is still considered the biggest challenge for today’s COVID-19 vaccines.