Go with the flow: how helpful is mass testing?

6 April 2021

2:40 AM

6 April 2021

2:40 AM

Over half the adult population has been vaccinated, new infections and deaths have plummeted to their lowest level since last September — and the government chooses this point to launch a programme to test every adult for Covid twice a week. The Prime Minister is due to announce this afternoon that lateral flow testing kits will be distributed by the million, free of charge to anyone who wants them. We will all be encouraged to test ourselves — and be placed under an obligation to self-isolate if they are positive.

Why? We have spent the past three months on a massive vaccination programme, using vaccines that have proved pretty well 100 per cent effective at preventing deaths and serious illness. Recent estimates suggest that as many as 60 per cent of the population now has Covid antibodies compared to just over 10 per cent in December.


And yet we’re now adopting a programme of mass testing. Does the government not believe in the efficacy of those vaccines? Last year it was telling us that 60 per cent of the population would have to be vaccinated or to have had the disease in order to achieve herd immunity. Yet the government now acts as if vaccination cannot on its own kill off the epidemic.

What is being introduced this week has its roots last summer, when we were trying to control the pandemic without any sign of the vaccines. It is the enactment of ‘Operation Moonshot’, which the Prime Minister announced last September — and which in the same month leaked documents showed would cost £100 billion (by contrast, the National Audit Office suggested at the end of last year that the UK was spending £12 billion on vaccines). The cost of mass testing would have been hard to justify at any point, but at least in pre-vaccine days there was a strong incentive to spend large sums on testing to get the country back to normal. Yet if you look at Britain’s Covid data compared to the rest of Europe, we seem to be doing well without mass testing.

But the cost of an ill-conceived testing programme goes deeper than just the price of the tests themselves. An assessment of lateral flow tests by Oxford University and Porton Down last year put the rate of false positives at 0.32 per cent, rising to 0.39 per cent in tests performed in the community, as opposed to under laboratory conditions.

That might sound reassuringly low, but if everyone in Britain were to test themselves twice a week it would mean 500,000 people being forced to self-isolate when they weren’t actually infected each week. That itself could impose a huge extra burden on the economy — as well as the loss of freedom. False positives are not such a concern when prevalence of Covid is very high in the community, but when real cases are low false positives will inevitably account for a far higher proportion of all positive results.

According to last week’s ONS infection survey (which is based on testing a randomised sample with more accurate PCR swab tests) only one in 370 people were found to be infected. These tests will no doubt catch many of those infections, but with so many of the elderly and vulnerable already vaccinated, the risk of those infections has thankfully been reduced. We know the vaccines are working. If you look at daily deaths, figures are in the low double digits and falling.

For those who do get a positive result, the government has said they could be given a PCR test to confirm it. But that is just adding more cost — and presumably people who return a positive lateral flow test will be forced to isolate while they await their PCR test result.

Mass testing could at one point have been part of the solution to tackling Covid-19. To introduce it at a moment when prevalence is very low and vaccination has worked so well seems deeply confused — a case of no one being quite brave enough to ditch an initiative that was conceived before vaccines had made it redundant. <//>

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