The omicron variant of coronavirus can partially evade the protection afforded by vaccines, according to laboratory tests conducted in South Africa that give one of the first indications of vaccine effectiveness against the variant, but scientists say the shots should still defend those inoculated from severe disease.
Scientists at the Africa Health Research Institute in South Africa tested the blood of 12 people vaccinated with the shot developed by Pfizer Inc. PFE, +0.47% and Germany’s BioNTech SA BNTX, +8.17% against the omicron variant to determine how effectively it neutralized the virus.
They found the vaccine generated one-fortieth of the infection-fighting antibodies against omicron compared with its performance against the original version of the virus. That is a big reduction but doesn’t mean the variant can escape vaccines completely, said Alex Sigal, the virologist who led the study.
“The vaccine takes a hit but it is not a completely different ballgame,” he said on a video call with reporters. He said the findings are preliminary and estimates of effectiveness may change as more data becomes available. His team’s experiment didn’t study other types of immune responses that scientists say are critical in determining vaccines’ overall potency against disease.
The results, published late Tuesday, came as government officials and scientists said that omicron is weeks away from becoming the dominant strain in parts of Europe and other evidence from the U.K. and Norway suggested that vaccines may offer significant protection against severe illness from the variant.
An expanded version of this report appears on WSJ.com.
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