The risk of virus mutations is likely to get worse before it gets better

The danger of new mutations of SARS-CoV-2 appearing and getting a grip in Britain and around the world will increase before eventually starting to fade.

This is the broad conclusion of scientists who are trying to predict how the virus will develop. Their work has implications for the global rollout of vaccines and for national policy, too.

Initially, countries will move from a position of high infection and little immunity to lower prevalence and high immunity. At the start, there is little pressure on the virus to adapt, but this grows as our immunity kicks in.

But the point of maximum risk occurs at the peak of the curve, says Prof Adam Kucharski, of the London School of Hygiene and Tropical Medicine, as it’s a function, not just of pressure, but the virus’s prevalence.

“The highest rate of adaptation occurs during the intermediate phase, when there is still enough transmission to generate new variants as well as enough immunity to create an advantage for variants that can evade this immunity,” he says.

It is hard to say where Britain sits on the curve because we can’t be sure of future prevalence but, with antibody levels in the population at around 1520 per cent and a high but falling incidence of infection, we are probably not yet at the peak.

There is a separate but related issue – the extent to which the fast-moving UK variant might be expected to keep more worrying strains of the virus that contain the E484K mutation at bay.

This mutation, nicknamed “Eric” by some scientists, was first seen in South African and Brazilian strains but has started to arise independently because it confers an advantage – the ability to at least partially evade our antibodies, naturally acquired or vaccine-induced.

Last week Prof Jonathan Van-Tam, the Deputy Chief Medical Officer, inspired a perverse patriotic cheer when he noted high transmissibility of the UK variant was currently keeping versions of the virus carrying Eric at bay, but that’s not the whole story.

The more we vaccinate to protect against the UK variant, the lower its relative transmission advantage becomes vis-à-vis variants with E484K.

This could prove a problem for the UK because the Oxford/AstraZeneca vaccine appears to offer less protection against variants containing the E484K mutation than those produced by Pfizer and Moderna. Research produced last week on the Pfizer jab suggested that a double dose was probably required to reliably fend off E484K strains.

The most obvious implication for policy is to lower the risk by driving down infection rates here and abroad.

“The more people infected, the more virus there is,” said Sir Jeremy Farrar, director of the Wellcome Trust. “Unless the UK wants to close its borders forever, it’s going to have to get rid of the virus or reduce it to a level [low enough to manage].”