Could a new mutation in the SARS-CoV-2 virus reduce the effectiveness of vaccines?

14:31 28.11.2020(updated 15:28 28.11.2020) Short URL

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Scientists are working hard to develop an effective Covid-19 vaccine, but a recently discovered mutant strain could dampen the effectiveness of some.

As the world grapples with developing a vaccine for Covid-19, some scientists warn that its effectiveness could diminish if the coronavirus progresses rapidly. Therefore, a mutated version of the virus, N439K, which began circulating in the summer of 2020 in Scotland was subsequently discovered independently in continental Europe and the United States.

“There are many Sars-CoV-2s in circulation in the world, and therefore many mutations,” said François Balloux, professor of genetics at University College London, quoted by Le Figaro. But none of the mutations gave an obvious replicative advantage […] According to our work, it seems rather to have benefited from a favorable environment “.

The peculiarity of the N439K mutation is that it affects a very sensitive region of the virus: that of the Spike protein which allows it to enter human cells, through cellular receptors of the ACE2 type. This is where neutralizing antibodies attack.

“Several studies have shown that neutralizing antibodies can remain in the body for up to six months after infection. But if this protein is modified, the antibodies no longer recognize it, or less well, and no longer, or not as much, protection, “Pascal Meylan, Swiss specialist in infectious diseases and honorary professor at the University of Lausanne.

This could mean that even before they are distributed, vaccines are less effective.

“This is a possibility that unfortunately cannot be ruled out, Judge Pascal Meylan. But there are several reasons why N439K, as well as other mutations, can be controlled. “

Therefore, in addition to the production of antibodies, the body develops a so-called cellular response: T lymphocytes target infected cells to eliminate them.

“Studies have shown that nearly 17 years after a Sars-CoV-1 infection, the body keeps the cellular response in memory,” comments François Balloux. Without neutralizing antibodies, the response is a little slower and does not prevent the onset of some symptoms. But it might be enough to prevent severe forms. “

Cellular immunity

A team of scientists from the Karolinska Institutet (Sweden) for its part has referred to all the data in the scientific literature on cellular immunity to SARS-Cov-2.

“This immunity seems quite effective, explains Marion Humbert, co-author of this work, to Figaro. Individuals who do not have antibodies in their blood sample can also be protected against reinfection. Furthermore, a part of the population is likely to benefit from the protection due to infection by other viruses: cellular immunity developed previously, in response to some viruses other than Sars-CoV-2, could protect against severe forms of Covid- 19 “.

However, the immune system is complex and for some, different responses cannot be ruled out, explains François Balloux.

“The main goal of vaccines is to create neutralizing antibodies against the Spike protein, but to generate a broader immune response,” notes Pascal Meylan. It will take time to judge the real degree of this protection. “