Viral variants and vaccination – Will the SARS-CoV-2 variants make vaccination more difficult? | Scientific technology

VIRUS ARE EVOLVING by natural selection. Each time they replicate, changes can infiltrate their genetic material. If this is advantageous, these will make the variants that display them prosper. One consequence is that these variants spread quickly.

Predictably, then, new variants of SARS–VSTheV-2, the virus that causes covid-19, has started to appear around the world. Four are particularly worrying. OOne, first detected in Britain in September, is 25 to 40% more transmissible than the original wild-type virus according to the latest estimates from British health authorities. A second, identified in South Africa a month later, has been linked to higher viral loads in the throat and nasal swabs. This makes it easier to spread. Two more emerged in America (July) and Brazil (December). And this week, a variant of the British variant was also detected, now sporting a mutation also found in the South African variant. There is no strong evidence to suggest that any of these newer variants are more lethal than the wild type, but researchers are concerned that one or more of them could escape existing vaccines.

The particular causes of this concern are mutations in the gene that encodes a protein called peak, which is found on the surfaces of SARS–VSTheV-2 viral particles. This protein is the means by which the virus enters cells. B.1.1.7, the viral variant first found in Great Britain, has more than 20 mutations, not all in the peak gene. But the one that helps lock the peak onto its target on the cell surface, a receptor protein called AS2. The variant first found in South Africa, known as B.1.351, has fewer mutations than B.1.1.7, but three of them appear to enhance resistance to the antibodies that people develop in response to the wild-type virus.

This increased resistance has raised fears that the variants in question may escape the immunity that people have acquired from previous infections or vaccinations, especially since all vaccines currently in use are intended to elicit an immune response to the disease. peak. According to the U.S. Centers for Disease Control and Prevention, the variants will need to accumulate multiple spike mutations to escape vaccine-induced immunity. Nonetheless, trial results announced on January 28 showed that an injection made by Novavax, a US pharmaceutical company, which was almost 90% effective in preventing symptoms of covid-19 in Britain, was not only 50-60% effective in South Africa. Johnson & Johnson, another American company, found a similar result while testing its single-dose vaccine in South Africa, the United States and parts of Latin America. Its vaccine is also less effective in South Africa than in other countries. This suggests B.1.351 is less suitable for existing vaccines than its predecessor. Even so, the vaccines have worked well enough to prevent serious illness in most cases.

Vaccine manufacturers will need to continue to adapt their vaccines to keep up with mutations in the years to come. This can be done by providing booster shots suitable for different variants, or by creating bivalent vaccines that work against both the original strain and a mutant. Moderna, the maker of a vaccine that has already been approved for use in several locations, plans to work on a booster that will improve the body’s immune response to B.1.351 and could work in combination with all other major vaccine candidates. Clinical trials of this approach are expected to begin in July and should be completed within a year. Pfizer and BioNTech, the partners who created another widely approved vaccine, say they can produce a vaccine suitable for the new variants in six weeks. The US Food and Drug Administration, that country’s medical regulator, has promised a “streamlined” process for the authorization of updated vaccines. This would be met by small trials to make sure that a modified vaccine elicits an appropriate immune response, rather than the large so-called phase three trials needed to test a completely new product.

So researchers are still learning how the new variants behave. But at the end of the day, the best way to stop a virus from growing is to stop it from spreading by any means available. All the more reason to vaccinate as quickly and as widely as possible. ■

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This article was published in the Science and Technology section of the print edition under the title “Enigma variations”