Testing’s Ability to Contain Virus Overstated, Study Finds

(Bloomberg) --

Mass testing for the coronavirus may do no more to stop the pandemic than quarantines and contact tracing alone, according to a new study.

While testing is critical in assessing the spread of the virus and the risks of lifting lockdowns, the containment benefits may be limited to certain high-risk groups such as health-care workers, according to the report from Imperial College London researchers.

The study wades into a thorny political debate, with the World Health Organization and other groups urging earlier and more widespread testing. Governments in the U.K., the U.S. and other places have faced criticism that a shortage of diagnostics allowed the virus to spread. Countries with aggressive testing regimens, like Germany and South Korea, have shown effectiveness in controlling it.

The U.K. abandoned widespread testing in the community last month, instead focusing on trying to delay the spread of the virus through social distancing. A study by other Imperial College researchers, showing the potential for hundreds of thousands of deaths if business went on as usual, was seen as instrumental in persuading the government to lock down.

“There has been substantial pressure on the U.K. government and others to ‘test, test, test’ in response to the Covid-19 pandemic,” Nicholas Grassly, an Imperial professor and one of the authors of the new study, said in an emailed statement. “We find that testing is most useful when targeted at high-risk groups such as health-care and care-home staff.”

Weekly Screening

Weekly screening of health-care workers and others at higher risk is estimated to reduce their contribution to the spread of the illness by up to 33%, the study found. But widespread testing is unlikely to limit overall transmission more than contact tracing and quarantine based on symptoms alone, it found.

Swiss giant Roche Holding AG, which brought out one of the first coronavirus tests in January, doesn’t think that type of diagnostic can be scaled up as widely as many would like. These molecular tests that look for the virus’s nucleic acids in someone’s nose or throat are simply too complex, Chief Executive Officer Severin Schwan said on a media call Wednesday. There also aren’t enough high-speed, high-volume instruments in the world’s laboratories that can do these screenings, he said.

As such, these tests -- which have diagnosed more than 2.7 million people globally -- should be reserved for populations already showing symptoms and people who work in critical jobs, such as doctors and nurses. One problem with scaling up this technology is that these tools can only identify if a person is currently infected. So someone could test negative in the morning, then get infected later in the day. “You would have to test everybody, everyday,” Schwan said. “It is an absolute illusion.”

In May, Roche will start selling antibody tests that could show if someone has already been exposed to the virus and potentially developed some immunity. That technology is easier to scale up, because there are often fewer components and there is a lot more equipment to conduct the tests. Such tools could be key in helping governments more safely reopen economies.

And yet, so-called “immunity passports” -- based on tests for antibodies or infection -- face significant technical, legal and ethical challenges, according to the Imperial College report. Officials and scientists in a number of countries are considering giving certificates to people who’ve recovered from Covid-19 that would allow them to escape restrictions, while the uninfected might have to remain isolated until a vaccine or treatment is found.

©2020 Bloomberg L.P.