Test, test, test – the World Health Organization famously recommended at the start of the pandemic.
And that is just what the UK did, quickly growing one of the biggest Covid testing infrastructures in the the world.
At the peak, more than 2m tests a day were being carried out and logged. It has given the UK arguably the best data on Covid infections of any country in the world.
But now ministers in England have taken an axe to the testing programme – and it is a decision that is likely to have implications for Scotland, Wales and Northern Ireland as much of the infrastructure and supply chain is organised by the UK government.
From 1 April access to all types of testing in the community – both the PCR tests offered to people with symptoms and the rapid lateral flow tests used to check for asymptomatic infections – will go.
The only exceptions are social care staff and those deemed at-risk. The latter group has yet to be defined, but is likely only to include those people who are eligible for antiviral treatments that need to be given early on to try to prevent hospitalisation.
That means the most vulnerable, such as organ transplant recipients and people with severely compromised immune systems. An otherwise healthy 80-year-old would not fall into this category.
It is a more dramatic move than many had thought would happen. There had been talk behind the scenes of some kind of rapid-test-on-prescription so older people and those with health conditions would be able to access tests to screen friends and family before they visit.
But that has not materialised. Many accepted some scaling back was needed, given the cost and protection provided by the immunity built up by vaccines and – to a lesser extent – previous infection.
After all, £37bn had been set aside for test and trace since the start of the pandemic. That is a huge sum: more than has been budgeted for GP care during that period. Not all of it has been spent, but a significant proportion has.
Would it be better invested elsewhere? The truth is we do not know as no cost-benefit analysis has been done to assess the merits of mass testing.
Prof Allyson Pollock, a public health expert at Newcastle University, is frustrated by this. "Many public health doctors and scientists do support ending mass testing and instead of wasting billions on tests would rather see money re-invested in social care, health care and schools."
To judge the move, you also need to look at what testing is used for and how what has been announced affects that.
It can be used for surveillance – to track the spread of the virus. And while community testing is going, the government has committed to keeping the Office for National Statistics survey, which provides weekly estimates for the number of people infected, albeit in a slimmed down format.
Prof Sir Chris Whitty, England's chief medical officer, says this will be vital in making "good policy decisions" in the future as we will know what is happening with the virus.
Another use of testing is to diagnose for clinical treatment. Patients who are seriously ill and need to be admitted to hospital will still get tested so they can get the right therapy for acute Covid and – as already mentioned – those eligible for antivirals will be entitled to testing in the community.
Testing is also important to look at what sort of variants are circulating – and that requires the PCR tests that are processed in a lab. But that can be done via the ONS survey and those who are tested in hospital. That is how we keep track of the strains of flu circulating.
The fourth major reason to test is to screen – to see if people are infected so the chances of them passing it on can be reduced.
This, of course, is what the move announced by the prime minister affects.
The majority of the public will not now be able to find out if they have Covid even if they have symptoms unless they pay privately for tests.
Instead, it will be up to those who are ill to decide whether to stay at home – as they do for other infections.
Prof Christina Pagel, from University College London, believes this, coupled with the removal of financial support for isolation will "disproportionately" affect more deprived communities.
"They will be less able to afford testing, less able to isolate and more likely to work outside the home and potentially infect others."
Others have made a similar point. But it is also important to recognise the current system was not perfect – and so the changes may have less impact than first assumed.
Firstly, people with the virus are infectious before symptoms develop, blunting the ability of testing to curb spread, and, what is more, only around half of people getting infected were coming forward for testing anyway.
"The move may make less difference than we think," says Dr Raghib Ali, a clinical epidemiologist at University of Cambridge and a front-line doctor.
That's because, he says, those that were coming forward for testing were likely to isolate in the future if they had symptoms, while stopping access to testing for people who were not getting tested in the first place would, of course, have no impact on the spread of the virus.
"Given current trends in infections, by April prevalence could be very low," he adds. "What's important is that we have the ability to ramp testing back up if we need to."
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Covid: An axe has been taken to testing – does it matter? – BBC