Will covid-19 vaccines work against new variants of the virus?

VIRUSES EVOLVE over time through natural selection. Every time a virus replicates, changes can creep into its genetic material. The more viral replication there is, the greater the chances that mutations will arise. And change brings potential problems in the fight against SARS-CoV-2, the virus that causes covid-19. Predictably, variants of the coronavirus have started to appear in several parts of the world. One, first detected in Britain in September, is 25-40% more transmissible than the original, or wild-type, virus, according to latest estimates by English public-health officials. Another, identified in South Africa a month later, has been linked to higher amounts of virus in people (measured using throat and nose swabs), which make it easier for it to spread. Two other variants emerged, one in America (July) and the other in Brazil (December). There is no strong evidence to suggest that the variants found so far are more deadly than the wild-type, but experts are increasingly worried that they may be more likely to evade existing vaccines.

In many ways the world has been lucky: SARS-CoV-2 has mutated at a much slower pace than other viruses, such as those that cause influenza. This may be because of its ability to repair some genetic errors as it replicates. Even so, the variants that have arisen are cause for concern because some mutations involve the gene that codes for the viral spike protein. Crucially, this structure is the means by which the virus gains entry to, and infects, human cells. The variant of the virus found in Britain, B.1.1.7, comprises more than 20 mutations, but at least three have been linked to greater infectiousness. One helps lock the spike onto its target on the cell surface, a receptor protein called ACE2. Similarly, the variant found in South Africa, B.1.351, has at least three mutations that appear to be more resistant to the antibodies that humans have developed to the wild-type virus. These sorts of changes have caused concern that the variant might be able to evade any immunity people had gained from previous infections or vaccination.