Mass testing alone isn’t enough to get England out of lockdown

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When Boris Johnson announced his landmark Operation Moonshot programme in early September – an ambitious plan to test millions of people for coronavirus each day – few expected that two months later, the UK would be looking to Slovakia as an example of what might be possible.
After all, the Eastern European nation has hardly hit the headlines as a Covid-19 hotspot. It recorded its first case in early March, and during the first wave of the pandemic, infection rates rarely exceeded 100 per day. But with daily cases reaching new heights amidst the second wave, prime minister Igor Matovič announced that Slovakia would use rapid antigen tests to conduct the first large-scale population testing program in Europe, in a bid to avoid a national lockdown.

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Dubbed Operation Joint Responsibility, the country has now conducted more than six million tests since October 23. The program began with a pilot study of 140,951 people from Oct 23 to 25, before testing two thirds of the population – some 3.6 million people – from October 30 to November 1, and half the population over the past three days.
So far, it appears to be working. From a peak of 3,363 new infections (in a population of 5.45 million) on October 31, daily cases had dropped to 2,579 by November 8, boosting hopes that mass testing can help quash the second wave. “The situation had become really bad in the past few weeks, with increasing numbers of hospitalised cases, and deaths,” says Alexandra Brazinova, an epidemiologist at Comenius University in Bratislava. “The pilot study targeted the four most affected districts in the country, and the proportion of positive cases in districts was found to have dropped by half during the second round of testing, because many people had already been identified and isolated the weekend before.”
Now Johnson is looking to apply a similar strategy to the UK, in a bid to end the current lockdown, and avoid further restrictions over the winter. A pilot scheme has just begun in Liverpool – one of the UK’s worst hit areas – offering so-called lateral flow antigen tests to anyone living or working in the city, through an online booking service, with the aim of screening around half a million people. They are available at various sites including hospitals, care homes, schools, universities and workplaces.
Because these portable tests simply use antibodies to detect the presence of specific viral proteins in nasal swabs, it means they can return a result in as little as 15-30 minutes. In comparison, the gold standard PCR test, which detects the presence of viral RNA, requires complex laboratory processing techniques to amplify its genetic material, and so can take up to 48 hours to process a result.

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If successful, the government plans to distribute millions of the tests across the UK between now and Christmas, with the aim of using them to drive down transmission in different regions. However, some scientists have already expressed concerns. As Jon Deeks, professor of biostatistics at the University of Birmingham points out, it isn’t the testing itself which helps curb the spread of the virus. Transmission rates only go down when people actually self-isolate following a positive result.
In Slovakia, people have been given little choice but to comply with the government’s program. Anyone who refuses to take a test must stay at home for ten days, with no salary. In the UK where the scheme will be voluntary, there is a risk that some individuals may opt not to take the tests unless they have adequate support to help them isolate. “In the UK, we’re still not supporting to isolate properly,” says Deeks. “If people on zero hours contracts can’t get funding to feed their families, they’re not going to isolate and they probably won’t go for testing.”
Scientists are also perplexed that many key details of the Liverpool pilot remain somewhat opaque, and Deeks says that the country’s National Screening Committee appears to have been excluded from the scheme. “We don’t know enough about what the government is doing here, or the science they’re using,” says Deeks. “The Department of Health is being incredibly secretive about what it is going to do, and how this pilot is going to be evaluated. There’s a National Screening Committee which we’ve had in the UK for 20 years, and they’ve been sidelined from this. There’s a big concern that we’re not going to learn what we should because we don’t know what studies are being done alongside it, and the right scientists haven’t been involved.”
One of the key concerns surrounds the government’s choice of rapid antigen test, which reports suggest is one being produced by a company called Innova Tried and Tested. While rapid tests are much faster than conventional PCR tests, the trade-off is that they tend to be far less accurate. Like most rapid tests, the Innova test was developed and validated on patients with severe Covid, but there is little information about how well it works on the general population, particularly the mild cases and asymptomatic carriers which the government is hoping to identify.

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“Like all the other rapid tests, this one has got concerns that it’ll miss people,” says Deeks. “Either because the swab taken doesn’t have much virus on it, or because they have a lower viral load. That can be because they’ve only just got infected and they won’t become symptomatic for a few days. The test will detect some but it’ll miss a lot.”
For an example of this, you only needs to look to Slovakia. The country’s mass testing program is being done using a rapid test called SD Biosensor. While this has a sensitivity – the ability to correctly identify people with Covid – of 76.6 per cent, when used on patients who are severely ill, this drops markedly when applied to the general population. Brazinova points to a series of studies which have shown the average sensitivity of a number of rapid tests, including SD Biosensor, to be just 56.2 per cent, meaning that it misses nearly half of all Covid-19 infections.
While the UK government has conducted its own independent assessments of the Innova test at its Porton Down laboratory, the results of these have not been made publicly available.
But despite these issues, Slovakia has demonstrated in recent weeks that rapid tests can still be effective at driving down rates of transmission. Brazinova says that the best way of using them is to repeatedly target high incidence areas of the population in successive days or weeks, which reduces the number of cases missed.
The World Health Organisation has advised that rapid tests should be only used alongside conventional PCR tests to validate any positive results, and reduce the risk of false positives – people who erroneously test positive for the virus when they haven’t actually got it – a problem with any test when large numbers of people are screened. Deeks says there are mixed reports as to whether or not the government is doing this in Liverpool. “Some people have said they are going to do this, and others have said that we don’t know,” he says.
So could mass testing help end England’s lockdown? Scientists think that it could be effective, particularly through targeting regions where the R number is extremely high and the spread of the virus has threatened to get out of control. “I think that for situations like the one Liverpool’s got into where they have very high rates, other alternatives like track and trace aren’t going to work and they probably need to do something like this,” says Deeks.
But when it comes to rolling out such a program across the whole nation, there would likely be many hurdles. While the tests in the Liverpool trial are being conducted at special sites, scientists predict that this wouldn’t be viable on a larger scale. Instead, they say a national program would likely rely on many people voluntarily taking the tests in their own homes and accurately reporting the results. This would mean compliance could be a major problem, especially over the coming months when people have the freedom to socialise again.
“If tests are self administered there’s always the risk that people suppress a positive result and don’t own up to it,” says Simon Clarke, associate professor of cellular microbiology at the University of Reading. “If you’ve got a holiday booked or a ticket to the theatre which costs quite a lot of money and you can keep your positive test to yourself, are you going to do that? I suspect a lot of people would.”
Deeks believes mass testing could be used to suppress surges of the virus in different regions, and end the current lockdown. But he is unsure as to whether a mass testing program across the entire country would be a good use of the country’s resources. “This is a really expensive thing to implement and there are other choices we have, in terms of what we’re putting money into,” he says. “We still have public health teams who are underfunded to do track and trace, and people have been saying for six months that’s the way to control things on a national scale. There’s a cost effectiveness question here, and it’s not a case of mass testing or nothing. It’s this or some of the other alternatives.”
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