Vaccines targeting the highly transmissible delta variant may now be needed given its ability to infect people with fading immunity and potentially increased severity, researchers leading a large English study of COVID-19 shots have said.
A third wave of English cases has been driven by the delta strain among both unvaccinated people — especially those between the ages of 12 and 24 — as well as some people who had received COVID-19 shots, according to 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-19 symptoms was 59%, down from 83%.
"Development of vaccines against delta may be warranted,” in the light of evidence that the strain’s spike protein has mutated to a point where antibodies raised by current shots are becoming less effective, the researchers said.