MILLIONS of Brits are still at risk of catching coronavirus, a major study has warned.
Scientists at Imperial College London said immunity to the bug is “waning” as they noted a 26 per cent drop in positive antibody tests in three months.
They predict just 4.4 per cent of people had detectable antibodies to Sars-Cov-2 at the start of the second spike in early September.
The REACT study, one of the biggest to track the spread of Covid-19, found people who had positive swab tests and displayed common symptoms – a cough, fever and loss of taste and/or smell – had the strongest antibodies.
Meanwhile, they were lower in the elderly and those who had asymptomatic infection.
Hope reinfections will be ‘milder’
The scientists warn it could mean more people are at risk of catching Covid-19, and getting reinfected this winter.
Professor Graham Cooke, from Imperial College London, said it’s important to note that a large swathe of the population are “still vulnerable” to infection.
But he said scientists hope, if Sars-Cov-2 behaves like other coronaviruses, reinfections should be “milder”.
“The big picture here is that after the first wave, the majority of people were still susceptible,” Prof Cooke added. “The need for a vaccine is still very large.”
For some viruses like measles and flu antibodies can be detected for years after infection. But the scientists said Sars-Cov-2 antibodies were likely to follow the pattern of other coronaviruses and decline after six to 12 months after infection.
Second wave hits
Professor Paul Elliot, director of the study at Imperial College London, said the findings come as a recent rise in infections is starting to translate into a rise in deaths.
Yesterday, a further 102 people died of Covid across the UK as 20,890 more tested positive, bringing total infections to 894,690 and deaths to 58,164.
Speaking at a press conference, Prof Elliot said: “There is evidence of rising levels of infection so there’s continued transmission and this is now translating into hospital admissions and sadly, into deaths.”
The REACT study used home tests to analyse around 365,000 people in three rounds – 12, 18 and 24 weeks after the peak in early April.
The presence of antibodies itself doesn’t necessarily mean you’ll be protected
Prof Graham Cooke
They found antibody positivity dropped 26.3 per cent in the three months from June to early September, leaving an estimated 2.5 million (4.4 per cent) with a level of protection at the start of the second spike.
The findings showed between June 20 and July 13, at least 3.36 million adults in England had tested positive for the virus and had displayed antibodies.
Infections were highest in the 18 to 24 age group, and lowest in those aged 75 and older, suggesting shielding protected the vulnerable.
Professor Helen Ward, professor of public health at Imperial, said there was a higher prevalence in London, and among BAME communities and healthcare workers.
“We do think that this is a sign of ongoing transmission,” she told journalists. “We’re reporting no decline in prevalence in health workers, so no waning in these groups, which may indicate ongoing transmission and repeated exposure.”
Antibodies not the only answer
Experts said while antibodies play an important role in immunity, there may be other things at play.
Prof Jonathan Ball from the University of Nottingham, said: “Other arms of the immune system, for example cellular immunity, might also be key. It is essential we gain a better understanding of what protective immunity looks like.”
Meanwhile, Dr Alexander Edwards, at Reading University, said declining antibodies might not be bad news.
“What is not clear is how quickly antibody levels would rise again if a person encounters Sars-Cov-2 a second time,” he pointed out.
“It is possible they will still rapidly respond, and either have a milder illness, or remain protect through immune memory. So even if the rapid antibody test is no longer positive, the person may still be protected from reinfection.”
Prof Cooke added that the presence of antibodies does not act like a impenetrable shield.
“Hands, face and space, those rules are certainly still required and still need to be adhered to as best as possible,” he said.