VIRUSES EVOLVEER by natural selection. When they repeat, changes can occur in their genetic material. If it is beneficial, it will allow varieties to thrive with varieties. One consequence is that such variants spread rapidly.
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Predictable, then, new variants of SARS–CoV-2, the virus that causes covid-19 has started to appear all over the world. Four is particularly worrying. OOne, first spotted in Britain in September, is 25-40% more transmissible than the original wild-type virus, according to the latest estimates by English health officials. A second, identified a month later in South Africa, is linked to higher virus load in throat and nose swabs. This makes it easier to distribute. Two others emerged in America (July) and Brazil (December). And this week a variant of the British variant was also detected, with a mutation that also occurs in the South African variant. There is no strong evidence to suggest that any of these new variants are more lethal than the wild type, but researchers are concerned about the risk that one or more of them could evade existing vaccinations.
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–CoV-2 virus particles. This protein is the way the virus accesses cells. B.1.1.7, the viral variant first found in Britain, has more than 20 mutations, not all in the genes for a peak. But one that helps close its target on the cell surface, called a receptor protein ACE2. 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 be resistant to antibodies that humans develop in response to the wild-type virus.
This increased resistance has caused concern that the variants in question could evade the immunity that humans have acquired due to previous infections or vaccinations – especially since all vaccines currently in use are an immune response to peaks. According to America’s Centers for Disease Control and Prevention, variants will have to accumulate multiple mutations to evade the immunity caused by vaccines. Nevertheless, the results of trials announced on January 28 showed that a blow by Novavax, a US pharmaceutical firm, which was almost 90% effective in preventing covid-19 symptoms in Britain, was only 50-60 % was effective in South Africa. Johnson & Johnson, another US firm, found a similar result when they tested the single-dose vaccine in South Africa, the United States and parts of Latin America. Its vaccine was also less effective in South Africa than elsewhere. This indicates B.1.351 is less susceptible to existing vaccines than its predecessor. Nevertheless, in most cases the vaccines worked well enough to prevent serious diseases.
Vaccines will have to adjust their vaccines to keep pace with mutations next year. This can be done by delivering booster shots tailored to different variants, or by creating divalent vaccines that work against the original strain and a mutant. Moderna, the manufacturer of a vaccine that has already been approved in various places, plans to work on an enhancer that counteracts the body’s immune response B.1.351 and can work in combination with all the other leading 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 that have created another approved vaccine, say they can produce a stitch adapted to new variants within six weeks. The U.S. Food and Drug Administration, the country’s medical regulator, has promised a ‘streamlined’ process for authorizing updated vaccines. This will be satisfied by small trials aimed at ensuring that a modified vaccine elicits an appropriate immune response, rather than the large, so-called phase three trials required to test a completely new product.
Researchers are then still learning how the new variants behave. But ultimately, the best way to prevent a virus from developing is to spread it in any way available. All the more reason to vaccinate as quickly and as widely as possible. ■
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This article appears in the Science and Technology section of the print edition under the heading “Enigma Variations”