Omicron variant partially escapes protection from Pfizer vaccine, study finds


Boosters are also likely to protect people, Alex Sigal of the Africa Health Research Institute in Durban, who led the study team, told CNN.

This is the first experiment to directly examine how the Omicron virus might behave in people who have been vaccinated.

Tests in lab dishes using samples from 12 people who had been fully vaccinated with Pfizer’s vaccine showed that the Omicron variant could escape the immune protection built by the vaccine – but not completely.

“There is a very strong drop in neutralization of Omicron by BNT162b2 [Pfizer/BioNTech] immunity from the ancestral virus, ”Sigal said on Twitter.

“Omicron’s escape from BNT162b2 neutralization is incomplete. Previous infection + vaccination still neutralizes,” he added.

The results are good news, Sigal told CNN.

“I thought this news was very positive. I expected worse,” Sigal said in a telephone interview. The mutations that characterize the Omicron variant, he said, appeared to be able to allow it to further evade the immunity offered by vaccines.

But experience indicates that it is not. “It’s not a variant that has completely escaped,” he said. “It certainly escapes. It sure is bad. But it seems to me that there are ways to deal with it.”

Sigal’s team used human lung cells for the tests. The blood of six volunteers who had been infected and then vaccinated was better able to neutralize the virus, they reported in a study submitted to an online preprint site. It has not been peer reviewed.

“A previous infection, followed by vaccination or a booster, is likely to increase the level of neutralization and possibly confer protection against severe disease in Omicron infection,” Sigal’s team concluded .

The study does not reflect the actual infection with the virus.

He found a 41-fold decrease in the levels of neutralizing antibodies against Omicron in some of the samples, compared to those generated against one of the earlier strains of the virus – although it is not clear how this could translate into a reduction in the actual value. protection of life.

South African researchers find evidence that people are more easily re-infected with the Omicron variant than with other variants

That number will almost certainly change as more and more samples are tested, Sigal said. There is a lot of variation from person to person when it comes to the antibodies generated by the vaccination.

The researchers noted that the beta variant, which dominated South Africa until recently, also escapes immune protection. “The results we present here with Omicron show a much more extensive breakout,” they wrote.

Although the team did not test the variant of the Omicron virus against the blood of people who had received vaccine boosters, Sigal believes that people who were fully vaccinated and then boosted will be well protected against serious illnesses caused by the vaccine. Omicron variant.

“My impression is that if you get a reminder, you are protected, especially against serious illness,” he said. “It took a hit – a bigger hit than we’ve seen before – but it didn’t reduce it to insignificant levels.”

Other studies looking at immune protection against variants have shown that many Covid-19 vaccines create very strong immune protection that provides an additional cushion of immunity – so that even if one variant escapes part of the immunity, there are many left to protect people from serious illness. This also appears to be the case with Omicron, Sigal said.

Importantly, the virus always attacks human cells through the same route it always has – a molecular gate called the ACE2 receptor.

“Imagine if this virus found a different receptor to bind to? Sigal asked. “Then all of our vaccines would have been garbage,” he added.

Sigal is quick to say that this is a very early experiment involving just 12 people and hastily grown live virus samples. “We went from getting the samples to doing the experiments to get something in just a few weeks. It’s crazy,” he said.

The team plans to test more samples and test them against different vaccines, including the Johnson & Johnson vaccine, which has also been widely deployed in South Africa.


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