Omicron dodges part of the Pfizer vaccine protection 0:43
(CNN) -
The omicron variant of the new coronavirus partly escapes the protection offered by Pfizer's vaccine, but people who have been previously infected and then vaccinated are likely to be well protected, researchers working in South Africa reported Tuesday. .
Booster doses are also likely to protect people, Alex Sigal of the Africa Health Research Institute in Durban, who led the study team, told CNN.
It is the first experiment that directly analyzes how the omicron variant of the new coronavirus could behave in vaccinated people.
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Laboratory plate tests with samples from 12 people who had been fully vaccinated with the Pfizer vaccine showed that the omicron variant could evade the immune protection built by the vaccine, but not completely.
"There is a very large drop in omicron neutralization by BNT162b2 [Pfizer / BioNTech] immunity relative to the ancestral virus," Sigal said on Twitter.
"The omicron leak from the neutralization of BNT162b2 is incomplete. The previous infection + vaccination still neutralizes it," he added.
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The findings are good news, Sigal told CNN.
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"I think this news is very positive. I was expecting something worse," Sigal said in a telephone interview.
The mutations that characterize the omicron variant, he said, seemed to allow it to evade the immunity offered by vaccines to a greater extent.
But the experiment indicates that this is not the case.
"This is not a variant that has been completely escaped," he said.
"It certainly escapes. It is certainly bad. But it seems to me that there are ways to deal with it."
Sigal's team used human lung cells for the tests.
Blood from the six volunteers who had been infected and then vaccinated was better able to neutralize the virus, they reported in a study posted to an online preprint site that has not been peer-reviewed.
"Previous infection, followed by vaccination or booster, is likely to increase the level of neutralization and confer protection against severe disease in omicron infection," Sigal's team concluded.
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The study does not reflect an actual infection with the virus.
It 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 unclear how that could translate into a reduction in protection in the real life.
That number will almost certainly change as more and more samples are analyzed, Sigal said.
There is a lot of variation from person to person when it comes to the antibodies generated by vaccination.
The researchers noted that the beta variant, which dominated South Africa until recently, also evades immune protection.
"The results we present here with omicron show a much more extensive exhaust," they wrote.
While the team did not test the omicron virus variant against the blood of people who had received booster doses, Sigal believes that people who have been fully vaccinated and then booster doses will be well protected from severe disease caused by the omicron variant.
"My impression is that if you get a booster dose, you are protected, especially against serious illnesses," he said.
"It took a hit, a bigger hit than we've seen before, but it didn't reduce it to insubstantial levels."
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Other studies looking at immune protection against variants have shown that many of the COVID-19 vaccines create very strong immune protection that provides an additional buffer of immunity, so that even if a variant escapes some of the immunity, it remains a lot to protect people from serious illness.
That appears to be the case for omicron as well, Sigal said.
Importantly, the virus still attacks human cells through the same route it has always done: a molecular gate called the ACE2 receptor.
"Imagine if this virus had found a different receptor to bind to?" Sigal asked.
"Then all our vaccines would have been garbage," he added.
Sigal is quick to say that this is a very early experiment involving only 12 people and samples of live viruses that are quickly cultured.
"We went from getting the samples to doing the experiments to get something in just a couple of weeks. It's crazy," he said.
The team plans to analyze more samples and test them with different vaccines, including the Johnson & Johnson vaccine, which has also been widely deployed in South Africa.
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