Covid: Brazil variant of concern may reinfect up to 61% of people who have had coronavirus
Between 25% and 61% of people who have previously had Covid are susceptible to reinfection from the worrying Brazilian variant of concern, research from the city it originated in has suggested.
A study on the P1 Brazilian variant among people living in the city of Manaus found potentially high levels of reinfection, and that the variant was more transmissible than the original pandemic strain.
However, in the UK where the Kent variant is now dominant over the original, experts have cautioned that the study cannot be used to predict what may happen in Britain, and say it does not suggest that vaccines will not work against the variant.
Six cases of the Manaus variant have been found in England and Scotland, with experts having narrowed down one missing case (part of the six) to 379 households in the south-east of England.
According to the latest study, from organisations including Imperial College London, Oxford University and the University of Sao Paulo, blood studies suggest more than 67% of people in Manaus may have had Covid by October 2020.
There was surprise then when the city suffered another huge wave of coronavirus at the start of this year, so experts sought to find out why.
They found that the proportion of Covid cases that were the P1 variant grew from zero to 87% in about eight weeks.
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P1 was found to be 1.4 to 2.2 times more transmissible than other variants in Manaus, and was found to evade 25% to 61% of protective immunity from previous infection.
Dr Nuno Faria, reader in viral evolution at Imperial, told a briefing: "If 100 people were infected in Manaus last year, somewhere between 25 and 61 of them are susceptible to reinfection with P1."
He said more work was needed on patterns that might occur in other countries, adding: "We know that vaccines are effective and they can protect us from infection and from disease and death.
"This is a period to be optimistic about the future. The more we know about the virus, the better we’re able to protect against it and I think there’s no concluding evidence to suggest at this point that the current vaccines won’t work against P1."
Sharon Peacock, executive director and chair of the Covid-19 Genomics UK ((COG-UK) a group of organisations which analyse the genomes of coronavirus samples), said P1 had been found in 25 countries to date.
But she said the current study could not be used to speculate on the effectiveness of vaccines or how things will "pan out in other countries including the UK."
How the findings - which have yet to be peer-reviewed - "relate to United Kingdom is yet to be determined," she added.
She added: "At the present time I don’t believe there’s any threat to our vaccination strategy, or likely effectiveness."
Experts do not so far believe that the P1 variant is more transmissible than the Kent variant, which in itself is more transmissible than the original pandemic strain.
Scientists have cautioned against making any assumptions at this stage because of the lack of evidence over transmissibility and reinfection.
Researchers at the briefing agreed that the current six cases of P1 in the UK was a low number, and it was thought multiple introductions of the variant would be needed for it to take off.
Dr Thomas Mellan, from Imperial, said researchers have found a somewhat increased risk of death with P1 in Manaus, but this was in a city with “substantial healthcare failure” such as a lack of oxygen.
Meanwhile, a study in the journal Nature Medicine also suggested a risk of reinfection from the South African variant of coronavirus and that vaccines may be less effective against it.
It comes as one of the scientists behind the Oxford/AstraZeneca vaccine described real-world data on the effectiveness of the jabs as "stunning".
Professor Andrew Pollard, director of the Oxford Vaccine Group, welcomed the study from Public Health England (PHE) which found that protection against developing symptomatic Covid-19 was high in elderly people after a single dose.
Prof Pollard told BBC Radio 4’s Today programme the findings were "stunning", and this was for two reasons.
"First of all, because these data come from the hardest group to protect – those who are the frailest, the oldest adults in our population – and we’re seeing an 80% reduction in hospitalisation in that group, which is stunning," he said.
"Second… both of the vaccines performed exactly the same, there was no daylight between them.
"We’ve had all this difficulty with communication, particularly around Europe, with uncertainty about the evidence, whereas in the UK we’ve been rolling out both vaccines in the confidence that they would both give high levels of protection.
"And that’s absolutely what we’ve seen now in this real-world evidence – that whether you’ve had a Pfizer vaccine or the Oxford AstraZeneca vaccine, you have very high levels of protection.”
Prof Pollard said around 5,000 people are dying every day from Covid across Europe, where some leaders have shunned the Oxford vaccine for older age groups.
It comes as the number of weekly registered coronavirus deaths in England and Wales has fallen by more than a quarter to the lowest level since the start of the year.
Deaths involving Covid-19 among people aged 80 and over have also fallen more steeply in recent weeks – as vaccines are rolled out – than those among younger age groups.