Surge testing has been expanded to four London boroughs amid growing concern that the test and trace programme cannot contain a coronavirus variant that has shown increasing signs of vaccine resistance.
A total of 56 cases of the variant first identified in South Africa were found in the week to April 14, according to data released on Thursday, taking the total confirmed cases since it was first detected in December to 600.
The largest “surge testing” operation since the start of the pandemic was launched in the boroughs of Wandsworth and Lambeth on Tuesday, then extended to postcodes in Southwark and Barnet, as public health officials urgently try to halt the spread of the strain, named 501Y.V2.
“Surge testing works until the day that it doesn’t,” said Danny Altmann, professor of immunology at Imperial College London, adding that the variant could “completely devastate us” if health officials were unable to prevent it from spreading nationwide — like B.1.1.7 did at the end of last year.
While the first case of 501Y.V2 found in Southwark was believed to be linked to the initial cluster in Lambeth and Wandsworth, genomic sequencing indicated that the Barnet case was unconnected.
The new cases have caused concern in the government as several of those infected had received at least one shot of either the AstraZeneca or Pfizer vaccine, suggesting the variant may have been able to resist vaccine protection, according to one test and trace official.
Scientists have questioned whether the rapid rollout of tests in densely populated neighbourhoods will be sufficient to stem the spread of a highly transmissible strain, particularly when London is emerging from lockdown.
“I am extremely concerned that . . . the horse may have already bolted,” said Dr Zubaida Haque, a member of Independent Sage, convened as an alternative to the government’s top scientific advisory group.
The relaxation of lockdown rules in England this week and children’s return to school after the Easter break were “the perfect storm” for variants to spread, Haque added.
Scientists also fear that the 501Y.V2 variant may have a competitive advantage over the B.1.1.7 variant, first identified in Kent, as it appears it may be able to infect some vaccinated people due to mutations around its spike protein, which it uses to enter human cells.
The 600 identified cases of the 501Y.V2 variant in the UK compares with 209,492 of B.1.1.7, meaning that 501Y.V2 accounts for barely 0.3 per cent of Covid-19 cases.
British health officials are getting more adept at identifying cases, no longer relying exclusively on genomic sequencing — which takes several days — to spot variants. New PCR diagnostic machines can detect them within hours.
Experts say that procedures before and after cases are spotted are crucial — namely, swift and locally led contact tracing, and ensuring people come forward to test and isolate.
“It is an incredibly difficult balancing act to reopen our towns and cities as we simultaneously find these clusters,” said Halima Begum, chief executive of the Runnymede Trust, an independent race equality think-tank. “But it’s clear that testing alone risks being ineffective if not used in tandem with broader measures aimed at protecting the most vulnerable members of our communities.”