Researchers say vaccines targeting the highly transmissible delta variant may now be needed, given its ability to infect people with fading immunity and potentially increased severity.
A third wave of English cases has been driven by the delta strain among both unvaccinated people — especially those aged 12 to 24 — as well as some people who had received Covid shots.
This was revealed by authors of a study of samples from about 98,000 people in England.
The effectiveness of vaccines at stopping infection during the study period fell to 49%, the researchers estimated, down from 64% in a month earlier.
Vaccines’ protection against development of Covid symptoms was 59%, down from 83%.
The US, UK and Israel are among the most fully vaccinated countries in the world, yet all have seen surges in Covid cases and hospitalizations linked to the delta strain.