Fears Covid variants are escaping vaccines as cases of South African strain double

New Covid variants appear to be escaping vaccines, with the latest figures showing a doubling in cases of the South African mutation in the UK in the last month.

Meanwhile, 77 cases of a separate variant from India – which it is also feared may resist vaccines – have now been found in the UK. Health officials said these were "geographically well spread", meaning surge testing would not be used in an attempt to contain the mutation.

Data from Public Health England reveals that there are now 600 cases of the South African variant in the UK – up from around 300 a month ago.

Officials have embarked on the largest "surge testing" programme to date amid concern that a number of the infections in London involve people who had already been vaccinated. Importation of cases of the South African variant has long been of concern because of its ability to escape vaccines.

The outbreak in London is thought to have been triggered by an individual travelling from a country in Africa to the UK in February, with cases spreading to members of their household and then to a care home in Lambeth, which is understood to have suffered at least 23 infections.

Six in 10 of the residents who became infected are understood to have received the Astra Zeneca jab, while one of the 13 staff members with the variant had been given the Pfizer jab.

Residents of Lambeth, Wandsworth, parts of Barnet and Southwark are being asked to undergo Covid tests in a bid to identify cases, with tests rolled out to areas of Birmingham and Sandwell on Friday.

But NHS data revealed just half of staff at care homes for older adults have been vaccinated in the borough of Lambeth, the lowest uptake among all local authorities across England.

Scientists are also worried about the arrival of the new variant from India, which has a double mutation in the spike protein that may make it more able to evade the body's immune responses. It currently has the label of "variant under investigation" but could be designated a "variant of concern" if it found to be more infectious or resistant to vaccines.

Paul Hunter, professor in medicine at the University of East Anglia, said it features two mutations – E484Q and L452R – which "are causing people to be concerned".

"There's laboratory evidence that both of these are escape mutations," he explained.

"Basically, applying what we know about other human coronaviruses would suggest that this is going to be even less controlled by vaccine. But we don't know that for certain at the moment."

Covid rates in India are soaring, with more than 13.9 million confirmed cases and 172,000 deaths. Boris Johnson has scaled down a planned trip to the country because of its worsening virus situation. The Prime Minister was due to spend four days there at the end of the month, but a Number 10 spokesman said most of the meetings would be fitted into one day.

On Friday, Downing Street pushed back against suggestions that a decision on placing India on the travel "red list" had been delayed due to Mr Johnson's trip. All passengers arriving from "red list" countries are required to undergo 10 days in hotel quarantine.

Asked why India had not been put on the list, the Prime Minister’s spokesman said: "All our decisions when it comes to the 'red list' are based on the latest scientific evidence and data and public health advice. We won't hesitate to add countries or remove countries where we think it's fit to do so."