Hopes of loosening lockdown restrictions in England on 21 June have been boosted by new research suggesting two coronavirus vaccines give effective protection against a more infectious strain first detected in India.
Both the Pfizer and Oxford-AstraZeneca jabs were found to be almost as effective against symptomatic disease from the Indian-origin strain, designated B.1.617.2, as they were against the B.1.1.7 mutation, which remains the dominant strain across the UK and was first detected in Kent.
The study, published by Public Health England (PHE) on Saturday, comes after concerns that the India variant could throw into doubt the lifting of all restrictions in four weeks’ time.
Separate PHE data released on Thursday showed that cases of the B.1.617.2 strain had risen sharply in the previous seven days, up to 3,424 from 1,313 in the previous week. New infections were predominantly affecting towns in northwest England and London, although clusters had formed in other parts of the UK.
While the India strain is more transmissible than the Kent variant, there is no evidence yet to suggest it causes more serious disease.
Boris Johnson has been under pressure in recent days to provide clarity on whether or not he should deviate from England's roadmap, but has previously said there is no "conclusive evidence" to warrant a delay.
PHE's study, which took place between 5 April and 16 May, found that the Pfizer vaccine was 88 per cent effective against symptomatic disease from the India variant two weeks after the second dose, compared with 93 per cent effectiveness against the Kent strain.
Meanwhile, the AstraZeneca jab was 60 per cent effective, compared with 66 per cent against the Kent variant over the same period.
Both vaccines were 33 per cent effective against symptomatic disease from the India variant three weeks after the first dose, compared with about 50 per cent against the Kent strain.
Some 12,675 cases were analysed, including 1,054 of the Indian variant confirmed by genomic sequencing. The study included data for all age groups from 5 April to cover the period since the strain emerged.
Matt Hancock, the health secretary, described the results of the study as “groundbreaking”. “This new evidence ... proves just how valuable our Covid-19 vaccination programme is in protecting the people we love,” he said.
“We can now be confident that over 20 million people – more than one in three – have significant protection against this new variant, and that number is growing by the hundreds of thousands every single day as more and more people get that vital second dose," Mr Hancock added.
The study included data for all age groups from 5 April to cover the period since the strain emerged.
PHE said the difference in the effectiveness between the vaccines may be due to the AstraZeneca second dose being rolled out later than the Pfizer vaccine. Data also shows it takes longer for the AstraZeneca jab to reach maximum effectiveness.
There are insufficient cases and follow-up periods to estimate vaccine effectiveness against severe outcomes from the India variant but this will be evaluated over the coming weeks, PHE added.
Dr Jamie Lopez Bernal, consultant medical epidemiologist at PHE and the study's lead author, said there was more confidence in the data from the first vaccine dose compared with that from the second.
He told journalists on Saturday: “There are bigger numbers that have been vaccinated with one dose. So I think we classify that as moderate certainty around the first dose, but low levels of confidence around the second dose.”
However, Professor Susan Hopkins, PHE's Covid-19 strategic response director, said the data trend was “quite clear” and was heading in the “right direction”.
Asked about how the data could affect the easing of restrictions from 21 June, Prof Hopkins said it was “too early to say”.
She said: “One week post the last restriction lifting, we will be monitoring it very carefully.”
Dr Mary Ramsay, head of immunisation at PHE, added: “This study provides reassurance that two doses of either vaccine offer high levels of protection against symptomatic disease from the B1617.2 variant.
“We expect the vaccines to be even more effective at preventing hospitalisation and death, so it is vital to get both doses to gain maximum protection against all existing and emerging variants.”
A separate analysis by PHE indicates that the vaccination programme has so far prevented 13,000 deaths and around 39,100 hospital admissions in older people in England, up to 9 May.
Latest figures show that more than 50 million doses of coronavirus vaccine have now been given in England.
A total of 50,246,402 Covid-19 vaccinations took place between December 8 and 21 May, according to NHS England data, including first and second doses.