Researchers report more people with Covid-19 antibodies – and it’s creating a stir among scientists

Studies in Europe and the US find many people may have been exposed to the new coronavirus without knowing

There remain questions about whether they’re protected against further infection and whether it helps herd immunity

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Covid-19 antibody testing detects whether a patient has been exposed to the new coronavirus. Photo: AFP

Published: 2:30pm, 29 Apr 2020Updated: 11:30pm, 29 Apr 2020

Surveys from Germany, the Netherlands, and the United States have found antibodies in people not previously diagnosed with the novel coronavirus, suggesting more people than previously known were infected with the virus responsible for the global pandemic.

But many of the studies have sparked controversy, with experts raising concerns about the accuracy of antibody testing methods, how well the surveyed subjects represented the population and how much antibodies protected against Covid-19, according to a report in Science magazine.

While some specialists said higher numbers of unconfirmed infections – based on the presence of antibodies – reinforced the need for strict physical-distancing measures, others suggested it could allow for some easing of lockdown measures because there was progress towards herd immunity, or resistance among the general population to the disease.

The World Health Organisation’s guidance last Friday said that while some governments had suggested the detection of antibodies to the virus, officially called Sars-Cov-2, could allow people with antibodies to travel or return to work, “there is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection”.

While most who contracted the virus would develop an antibody response that could offer some level of protection, it was not yet clear what level of protection was provided or how long it would last, the WHO said.

German virologist Hendrik Streeck, from the University of Bonn, carried out a study this month in Heinsberg, which is an epicentre of the virus in Germany under strict lockdown. Streeck’s study found that 14 per cent of 500 people they tested had antibodies to the virus.

Julie Janke, a medical technologist at Principle Health Systems and SynerGene Laboratory, helps sort samples for different tests on Tuesday, April 28, in Houston. The company is offering a new Covid-19 antibody test developed by Abbott Laboratories. Photo: AP

The researchers said this meant the virus killed 0.37 per cent of those infected, concluding that “15 per cent of the population can no longer be infected with Sars-CoV-2, and the process of reaching herd immunity is already under way”.