science

Omicron can partially evade Covid vaccine protection, study finds


The Omicron variant of coronavirus can partially evade the protection of vaccines and previous infection, according to one of the first laboratory studies into the matter.

However, the findings suggest immune escape is “not complete”, which means that boosting antibodies can compensate for vaccines being less well matched to Omicron than to earlier versions of the virus. Scientists said that while the clinical implications were yet to be confirmed, the findings strongly supported the idea that booster vaccinations would be effective.

“It is likely that lesser vaccine-induced protection against infection and disease would be the result,” said Prof Willem Hanekom, the executive director of the Africa Health Research Institute, where the study was carried out. “Importantly, most vaccinologists agree that the current vaccines will still protect against severe disease and death in the face of Omicron infection. It is therefore critical that everyone should be vaccinated.”

The data, posted online on Tuesday, has not been peer-reviewed and is among the first to be released about the ability of our immune system to combat Omicron. The scientists tested the ability of blood from 12 people who had been vaccinated with the Pfizer/BioNTech vaccine to neutralise the Omicron variant, and compared this with the response to an early strain of coronavirus. Six of the people had been infected during South Africa’s first wave.

The scientists found a 41-fold reduction in the blood’s neutralisation against Omicron, but not complete immune escape. And blood from people who had received two doses of the vaccine and had a prior infection had “relatively high neutralisation [levels] with Omicron”, suggesting that booster doses of the vaccine could be effective.

It is not clear how these findings will translate clinically, but scientists expect to see a drop in protection against infection, but that T-cells, which work in parallel with antibodies, are likely to hold up better against Omicron and help protect against severe disease.

Announcing the findings on Twitter, Prof Alex Sigal, who led the work, said the results were “better than I expected of Omicron. The more antibodies you got, the more chance you’ll be protected from Omicron.”

Daniel Altmann, a professor of immunology at Imperial College London, said the study offered a clear message. “Those who are unvaccinated, or even two-dose vaccinated, are likely to be highly vulnerable to infection. However, those who’ve seen a spike three times, either by boosting or by infection plus two doses, appear generally in the safety zone, even with a 41-fold drop. So, an even stronger argument for getting boosters as widely and rapidly as possible.”

Paul Moss, a professor of haematology at the University of Birmingham, said: “The concerning finding is that antibody neutralisation is reduced by around 40-fold against Omicron compared to the original Wuhan virus. This means that only 2.5% of the antibody neutralisation activity is retained, but this sort of result was not unexpected given the mutational profile of the virus. Emerging evidence from booster vaccinations shows that they are capable of generating very high levels of antibody, which should potentially still provide valuable protection against infection.”

A second study, by a team at Sweden’s Karolinska Institute, found an average seven-fold drop in potency of antibodies against Omicron compared with the original strain. However, the response was variable across the samples tested, with some people’s blood showing no loss in immunity and others a more than 25-fold loss compared with the original strain.



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