How great is the threat of a new vaccine-resistant Covid variant?

The results of the UK’s much-lauded Covid-19 vaccine rollout is at risk of being undermined by new strains of the coronavirus, scientists are warning.

As the number of reported new cases continues to climb, Nobel-winning geneticist Paul Nurse told BBC Radio 4’s Today programme this week that if government opens up England “so much so fast” on so-called Freedom Day, “we could create a variant resistant to the vaccine”.

“Letting the virus spread in these circumstances encourages a new variant arising in the UK itself,” explained Francis Crick Institute director Nurse. His intervention came after government advisor Professor Neil Ferguson told the programme that the unlocking will be a “slight experiment”.

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What are the chances of a vaccine-resistant variant?

Scientists’ concerns have been fuelled by confirmed cases in the UK of a further strain of the virus, the Lambda variant, which was first detected almost a year ago in Peru. Experts fear that along with being highly contagious, the strain may be “more resistant to vaccines or antibody treatments”, The Independent reports.

Newly published research from the University of Chile found that the variant’s unique spike protein mutations “confer increased infectivity and immune escape from neutralising antibodies elicited by the inactivated virus vaccine CoronaVac”, which last month became the second Chinese vaccine to be approved by the World Health Organization.

As England gears up for the full lifting of Covid restrictions on 19 July, more than 120 scientists have signed an open letter published in The Lancet criticising Boris Johnson’s “dangerous and premature” unlocking plan. “Preliminary modelling data suggest the government's strategy provides fertile ground for the emergence of vaccine-resistant variants,” the letter says.

Concerns have already been raised about the effectiveness of Covid vaccines against known “variants of concern”.

A Public Health England-commissioned study investigating the success of vaccination against the Delta variant (first detected in India) found that both the Pfizer-BioNTec and AstraZeneca jabs were 33.5% effective after one dose, compared with 51.1% effective against the Alpha variant (Kent). However, after two doses only “modest differences in vaccine effectiveness” between the two strains were recorded, the study authors wrote.

The UK vaccination programme has now passed the point where more adults have received a first dose of a Covid vaccine than have not. According to latest government data, almost 65% of adults have had two doses, while 34 million further adults have had one.

Preliminary modelling by UK academics has found that the risk that a virus variant can “escape” the effectivity of a vaccine is highest at “intermediate levels of vaccination” - in particular, when the most vulnerable members of a population are vaccinated but not the less vulnerable. This latter group is referred to as “mixers”, as they tend to mix more with others compared with the “vulnerable” category.

And with the mixers set to do exactly that after social distancing rules are relaxed, some experts fear that a vaccine-resistant variant could emerge in the coming months.

What happens next?

Newly appointed Health Secretary Sajid Javid told the Today programme this week that the link between Covid infections, hospitalisations and deaths “has been severely weakened” by the national vaccine rollout. But “there may be, and no one knows this, a variant that comes out in the future that is vaccine resistant”, he admitted, adding: “We have to remain vigilant.”

The “control around our borders and the need to isolate from certain countries” will continue as part of the UK’s “wall of defence” to protect against the spread of new variants, Javid said.

However, criticisms of the virus defence strategy have increased after the government announced yesterday that fully vaccinated travellers returning to England from amber list countries will no longer have quarantine after Freedom Day.

Six of a total of eight Lambda cases recorded in the UK as of 2 July “were linked to overseas travel”, The Independent reports.

Plans to offer Covid booster vaccine doses to the most vulnerable ahead of what Johnson has warned may be a “rough winter” could help to prevent a further rise in infections later this year.

But the key question among scientists right now is whether the imminent lockdown lifting will see a more resistant variant emerge before most of the population has had two jabs.