Professor Jonathan Van-Tam said he wanted to reassure the public after a small study found the Oxford-AstraZeneca jab, one of two vaccines currently in use in the UK, was not effective at preventing mild illness caused by the South African variant.
Prof Van-Tam said the “most likely scenario” was that the variant, which has prompted door-to-door testing in areas where there have been outbreaks, would not become dominant over the coming months.
Early modelling suggested the variant did not have a “transmissibility advantage” over other forms of the virus, he said.
He added: “I don’t think that this is something that we should be concerned about right at this point in time.”
Ministers were putting contingency plans in place in case the variant meant high-risk groups in the UK could need a booster vaccine this autumn, he said.
But he added that scientists did not know yet if that would be necessary.
And he predicted any easing of lockdown restrictions in England would have to take place gradually, warning it was too early to say whether or not the public should start booking holidays for this summer.
“The more elaborate your plans are for summer holidays, in terms of crossing borders, in terms of household mixing, given where we are now, I think we just have to say the more you are stepping into making guesses about the unknown at this point,” he told a No 10 briefing.
“I can’t give people a proper answer at this point because we don’t yet have the data. It is just too early to say.”
Earlier, Boris Johnson did not rule out the possibility that the South African variant could delay the lifting of lockdown.
His comments came before the government announced urgent door-to-door testing would be carried out in six postcodes of Manchester where cases of the Kent variant have been detected.
But during a visit to a coronavirus test manufacturing facility in Derby, Mr Johnson said all the vaccines in use in the UK provided strong protection against serious illness and death.
“We’re very confident in all the vaccines that we’re using,” he said.
A separate study suggests that the other jab currently in use in the UK, produced by Pfizer and BioNTech, is effective against the South African variant. The UK has ordered millions of doses of other Covid vaccines, but these have yet to arrive in the UK.
Vaccines minister Nadhim Zahawi on Monday suggested that a “booster” vaccine to tackle new variants of the disease could be approved by regulators in just 30 to 40 days if based on an existing jab.
However, it could take another three to six months to manufacture enough vaccines to treat the population, he added.
Speaking at an event organised by the Tortoise news website, he also suggested that the public could receive combined Covid and flu vaccines in the future.
And despite the high take-up rates of the vaccine seen so far, Mr Zahawi said that ministers would be doing more in the coming days to increase them further.
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