In Brief

Coronavirus: UK herd immunity ‘may be closer than thought’

New study finds that antibody tests may be failing to identify large numbers of people who have been exposed to Covid-19

Many more people than previously thought are likely to have Covid-19 antibodies, according to new research that suggests the UK may be closer to herd immunity than previously thought.

“Current antibody tests fail to identify people who had mild infections,” scientists write in a newly published paper in the British Medical Journal.

One of the team behind the research, Dr Stephen Burgess of Cambridge University, says that widely used tests are also highly selective in what they can detect.

“It’s possible that somebody could have antibodies present in their saliva but not in their blood and it’s possible that somebody could have one class of antibody but not another class of antibodies,” he told The Times

“This might explain why, in cities such as London, we have seen the breakdown of widespread social distancing but infection rates have still not increased sharply.”

Random antibody testing suggests that 17% of Londoners and 5% of people across the UK have an immune response to the virus. But these figures refer only to bloodborne IgG and IgM antibodies, and not the IgA antibodies found in the mouth, eyes and nose, the new study paper says.

“IgA also has an important role in the immune response to respiratory tract infections and seems immunologically relevant in Covid-19, particularly in asymptomatic people,” the researchers report.

According to the scientists, 15% of UK health workers with negative results from standard antibody tests are found to have IgA antibodies. And in Luxembourg, IgA antibodies have been found in five times as many people as have IgG antibodies.

Many experts believe that at least 70% of the population would need to be exposed to the coronavirus before it would naturally stop spreading - resulting in large numbers of deaths.

But others, including Oxford University theoretical epidemiologist Sunetra Gupta, have suggested the figure could be more like 20%, owing to partial immunity resulting from exposure to related viruses.

“Her views have split the scientific community,” says ITV News. “While few disagree with the theory, they argue we don’t know enough to be sure that stepping back and allowing immunity to develop will work in practice.”

Burgess says that some scientists are reluctant to question the received wisdom about the prevalence of antibodies.

“We’ve been asking ourselves the question of why this has not got more attention,” he told The Times. “It is clearly very important to our understanding of the disease.

“I think scientists are cautious, and would prefer to say nothing if they are not sure, even when saying nothing also has consequences.”

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