Relaxing coronavirus restrictions could lead to new virus mutations that are resistant to vaccines, researchers have warned.

Experts at the University of East Anglia and the Earlham Institute cautioned against relaxing measures too early and described an “arms race” against COVID-19.

In an article for the journal Virulence, they argued that rising cases could provide opportunities for coronavirus to evolve into even more transmissible variants.

It comes as official figures on Monday showed the number of newly reported COVID cases in the UK dropped for the sixth day in a row – though the impact of the 19 July easing will not be known for several weeks.

Meanwhile, Boris Johnson has stressed the need for caution in light of those figures.

“We’ve seen some encouraging recent data, there’s no question about that, but it is far, far too early to draw any general conclusions,” the prime minister told LBC Radio.

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“The most important thing is for people to recognise that the current situation still calls for a lot of caution and for people just to remember that the virus is still out there, that a lot of people have got it, it still presents a significant risk.”

Lead author and editor in chief of Virulence, Professor Kevin Tyler from UEA’s Norwich Medical School, said: “Over the past 17 months, economies, education and mental well-being have suffered tremendously due to the restrictions imposed in an attempt to stem the spread of the pandemic.

“Although vaccines have weakened the link between infection and mortality, they should not be used as an argument to justify a broad change in policy for countries experiencing an exponential increase in infection numbers.

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“This is because most of the world’s population are still unvaccinated, and even in countries with efficient vaccination programmes, a significant proportion of society, particularly children, remain unprotected.

“Relaxing restrictions boosts transmission and allows the virus population to expand, which enhances its adaptive evolutionary potential and increases the risk of vaccine-resistant strains emerging by a process known as antigenic drift.

“Put simply, limiting the spread of Covid-19 as much as possible restricts the number of future deaths by restricting the rate with which new variants arise.

“Successive SARS-CoV-2 variants, such as the Alpha and Delta variants, have displaced one another since the outbreak.

“Slowing down the rate of new variant emergence requires us to act fast and decisively, reducing the number of infected people including children with vaccines and in combination with other public health policies.

“In most cases, children are not vaccinated against Covid-19 because the risk to them becoming seriously ill is very low.

“But new strains may evolve with higher transmissibility in children, and vaccinating children may become necessary to control the emergence of new variants.”

He said the policy of relaxing restrictions while children are not vaccinated risks the inadvertent evolution of virulent variants that are better able to infect children and are more problematic in vulnerable groups

Co-lead author and evolutionary biologist Professor Cock Van Oosterhout, from UEA’s School of Environmental Sciences, said: “We have an arms race on our hands.

“On the human side, the arms race is fought with vaccines, new technology such as the NHS Covid-19 App, and our behavioural change – but the virus fights back by adapting and evolving.

“It is unlikely we will get ahead in this arms race unless we can significantly reduce the population size of the virus.

“But given that the infection rate is about the same now as it was during the first wave, we are pretty much ‘at evens’ with this virus. And as with many other coevolutionary arms races, there are no winners.

“But what you cannot do is suddenly drop your guard in the middle of an arms race.

“So we must continue doing the things we have been doing for the past 18 months, particularly in countries where the number of infected people is increasing.”

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He added that entrusting public health measures to personal responsibility was a “laissez-faire approach”.

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