Covid-19: the Omicron variant can bypass vaccine defenses

Omicron, with its fifty mutations, will he jeopardize the vaccine strategy being deployed in the face of the pandemic? The first experimental studies raise concerns: several of them show a weakening of the immune protection offered by vaccines against this variant, while the cases of re-infections or infections of people already vaccinated are increasing.

This is what emerges in particular from data made public Wednesday, December 8 by the company BioNTech, which developed with Pfizer the most widespread messenger RNA vaccine. It’s about “Preliminary data”, warned Ugur Sahin, CEO of BioNTech, which moreover is based on the ability of a pseudovirus with the characteristics of Omicron, but not of the virus itself, to induce or not an immune response in vaccinees.

The tests were carried out on serum taken from around twenty people, either three weeks after the second dose or one month after the booster. Among the former, “There is a major reduction in the amount of neutralizing antibodies” against Omicron, compared to the immune defense erected by the vaccine against the initial so-called “Wuhan” virus (35 times less) or compared to the Beta variant (5 times less). The comparison with the Delta variant was not presented for the doubly vaccinated.

On the other hand, in people who have been vaccinated three times, the antibody response is only twice as low as when faced with “ancestral” SARS-CoV-2. It is even close to that observed against the Delta variant, for which we know that vaccine protection against severe forms of Covid-19 remains high. Ugur Sahin also referred to data on the cellular immune response carried by lymphocytes, believing that they “Will still be active against Omicron”.

“These data show that the line of defense provided by two doses could be compromised, said Ozlem Türeci, medical director of BioNTech and wife of the CEO. This prompts us to further investigate the option of a suitable vaccine for Omicron. “

Neutralizing power decreased by 41 times

Especially since the protection offered by this recall could weaken quite quickly. The team of Sandra Ciesek, from the University Hospital of Frankfurt (Germany), circulated on Wednesday on Twitter results, still unpublished on a comparison of the neutralizing power of sera three months after the booster of the Pfizer-BioNTech vaccine. He is 24.5 times weaker than against the Delta. But Moderna and AstraZeneca’s vaccines also saw their effectiveness compromised. “These data do not allow us to say whether or not you will always be protected against a severe course of the disease”, however, indicates the virologist, stressing the importance in this protection of T lymphocytes.

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