LONDON, United Kingdom (AFP) — Britain on Monday appealed for a person infected with a powerful COVID-19 strain from Brazil to come forward, as experts fretted about its impact on new vaccines.

The public appeal came a week before England is due to start slowly unwinding its third COVID lockdown, with progress hinging on the vaccines’ ability to curtail the pandemic.

The variant that emerged in Manaus, northern Brazil, has been detected in six people in the UK, one of whom cannot be located after they failed to fill in their contact details on a form after taking a coronavirus test.

Susan Hopkins, COVID response director at the government agency Public Health England, said the person was thought to have been tested on February 12 or 13, possibly via a home postal test or one collected from a local authority.

“We are looking at where the test may have been sent from and to, working with the postal services and the courier services,” she told BBC radio.

Vaccines minister Nadhim Zahawi said community-wide “surge testing” was starting in South Gloucestershire, western England, after two of the Manaus cases were confirmed there.

“We would pick up community transmission of this variant very, very rapidly, because we are able to genome sequence so quickly,” he said.

Prime Minister Boris Johnson played down any doubts about vaccine efficacy.

“We don’t have any reason at the present time to think that our vaccines are ineffective against these new variants of all types,” he said during a visit to a school that is preparing to reopen next week.

– Border gaps –

However, experts warned that based on data from Brazil, the variant was both more transmissible and better at evading antibodies than the UK’s predominant strain which emerged in the southeastern county of Kent last September.

“Manaus in particular reported that a number of individuals were re-infected with this variant, and therefore that suggests that having had prior immunity from primary infection wasn’t enough to reduce infection and transmission,” Hopkins said.

“And that may also impact on the vaccine.”

In mid-January, Britain banned flights from South America including Brazil, and introduced a mandatory hotel quarantine system a month later.

The two cases confirmed in South Gloucestershire were in the same household, after one of them arrived on a flight from Sao Paulo via Zurich on February 10 — five days before the hotel quarantine began.

Another three are Scottish residents who flew to Aberdeen from Brazil via Paris and London, who all tested positive while self-isolating.

Johnson defended his government’s handling of the borders as criticism grows about the late start of hotel quarantines.

“We moved as fast as we could to get that going,” he said.

Britain has Europe’s highest toll from the COVID pandemic, with nearly 123,000 deaths.

But on Sunday the government said it had given more than 20 million people at least one dose of a coronavirus vaccine, providing some hope that the end is in sight — unless new strains take hold.

Next Monday, schools across England are due to reopen to pupils for classroom teaching as part of a staggered return to normality over the coming months.

The government insisted there was no change to the timetable, pointing to a stepped-up regime of COVID testing for schoolchildren to spot any new infection trends early, and stressed the vaccines remain highly effective at reducing illness.