This past week, testing for Covid-19, or the lack of it, has been the main focus of criticism of the government’s handling of the pandemic.

Some of this criticism is undoubtedly deserved. A report by the Adam Smith Institute found that “The early decision [by health authorities] to centralise testing to a single Public Health England (PHE) laboratory has hampered the ability to increase testing in the UK”. Additional PHE and NHS laboratory resources were added and latterly university and private sector operators have been utilised, but the UK is still carrying our fewer tests than comparable countries like Germany and the USA.

But we should be a bit more wary of the idea that “more” automatically means “better” when it comes to testing. We should also be bit more concerned about what the implications of mass testing could be – in particular, what will government and authorities do with all of this test data?

It is possible that a comprehensive testing programme in the early stages of the outbreak in this country might have allowed the spread of the virus to be contained when only a handful of cases had been reported in people returning from affected countries and those they had had contact with. This kind of ‘track and trace’ approach was deployed in South Korea and (in one location) in Italy, with some success. But it would not have been viable to implement track and trace in this country – a full scale programme of taking temperatures and tracking movements via mobile phone apps – at the outset of the outbreak. With the information that was known at the time, the government would not have been able to embark on such action. It would not have had the facilities or the legal frameworks to do so, and it would not have been straightforward to pass any necessary legislation. There was no consensus in Parliament or wider society, including among scientists and epidemiologists.

In any event, that ship has now sailed. We are now faced with a very different question, which is: what is the value of mass community testing now, as opposed to the more limited testing of patients showing serious symptoms that is currently available? Clearly, testing NHS and other key workers who are currently self-isolating because they or members of their household have shown symptoms should be an urgent priority, so they can return to work if they test negative, and indeed this is now being acted on. Obviously, for scientific/epidemiological purposes, more and better data will be beneficial in mapping and modelling the outbreak and designing an exit strategy (although here, too, some scientists are sceptical, on the basis that more testing gives rise to a confirmatory “seek and thou shall find” effect).

In Germany, the other popular example of supposed good practice where hundreds of thousands of tests have been carried out, it has been argued that the vast majority of these tests (which are negative) are a waste of time. They use up consumables that are in short supply globally (notwithstanding fake news to the contrary), and they are only current at the exact time the test is taken. A person who tested negative could still pick up the virus five minutes later. Carrying out more testing, so far, does not appear to be alleviating the spread of the disease. In fact some specialists in Germany are arguing for more “intelligent testing” – a targeted approach that would allow testing to help determine the best treatment for those who present with symptoms – curiously similar to the approach in the UK to date. So maybe there is a bit of a “The grass is always greener on the other side” effect.

It is surely incontestable that PHE and the NHS got some decisions badly wrong in their approach to testing, a reflection on the dangers of centralised bureaucracy in healthcare. But at the same time, given that false negatives are common, and that faulty tests have been reported, there is some grounds for seeking some form of standardisation and quality assurance in the national testing approach. Of course, such QA does not have to be done by a government quango – as has been seen in Germany, where there is no suggestion that private laboratories and institutions have not been adhering to the highest quality standards.

Much of the debate on the effectiveness or otherwise of mass testing is within the realm of science and medicine, but there are vital questions of public policy in play, in particular around what authorities will be able to do with the results of tests. Clearly, testing data should inform individual healthcare decisions, and at a macro level, it should be used to direct resources and make strategic decisions. But applying testing in combination with real-time track-and-trace, as a way of bringing the epidemic under control, raises serious questions of privacy and civil liberties. The highly infectious nature of Covid-19 means that for contact-tracing to be effective, it has to be done in real time (as opposed to manually, by contacting people whom the diagnosed patient recalls having had contact with). This is done by using a mobile phone app to identify everyone who has been in proximity of someone who tested positive for the virus, and these people must then also be quarantined.

This system was used in China, where, as described in an article in Science magazine, the app was “not compulsory but was required to move between quarters and into public spaces and public transport. It allows a central database to collect data on user movement and coronavirus diagnosis and displays a green, amber or red code to relax or enforce restrictions on movement”. The authors put forward a model for a similar track-and-trace app that could be used elsewhere. Similar technology and measures are in place in South Korea. The scientific journal Nature describes the kind of data sharing that underpins the much praised South Korean approach: “When a person tests positive, their city or district might send out an alert to people living nearby about their movements before being diagnosed. A typical alert can contain the infected person’s age and gender, and a detailed log of their movements down to the minute — in some cases traced using closed-circuit television and credit-card transactions, with the time and names of businesses they visited. In some districts, public information includes which rooms of a building the person was in, when they visited a toilet and whether or not they wore a mask. Even overnight stays at ‘love motels’ have been noted.” The authors of the Science article acknowledge that the solution they put forward raises issues of ethics and data protection, but consider that they are outweighed by the benefits to public health, and can be mitigated by strong governance and oversight.

The possibility of an antibody test that will confirm whether a person has had the virus and is therefore immune from contracting it and carrying it raises the question of what it would mean to be certified immune. There have been suggestions that a wrist band or ‘immunity passport’ could be issued that would allow immune people to be exempted from lock down measures. The incentives that this would give rise to, and the implications for individual freedom are troubling. Who would be responsible for checking the passports? How would a black market be avoided? Could it really be justified to keep the remaining population under virtual house arrest? Would younger, fitter people simply be incentivised to seek out exposure to the virus so as to see off the virus and pass the test? On the other hand, if no such privileges were attached to testing positive for antibodies, could the lock down be maintained if millions of people know that they are immune and carry no risk?

Large sections of the population would surely resist or avoid testing and having their health data used by the state in the ways envisaged in passporting or track-and-trace solutions. It would also be disappointing if privacy regulators and campaigners, who in normal times applaud and oversee data protection laws that cause serious costs to businesses and organisations and prevent routine data transfers to the United States wave through these kind of intrusive measures. There are already indications that EU data protection supervisors are open to extraordinary levels of tracking and provision of location and communications data to governments and some member states have proceeded to go live with tracking apps. It is also possible that there will be less intrusive approaches to track-and-trace, that work on a voluntary basis and do not involve location and contact data being shared with governments or published.

So to all those calling for the government to “test, test, test” need to be clear about what they wish or expect authorities to do with the test results. As we have seen with the enforcement of the lockdown regulations that restrict our freedom movement outside of our homes, it is entirely feasible that authorities will over-interpret and exploit any powers and restrictions that might be associated with use of testing data to control the movements of individuals or entire communities. The British people and media have also taken to surveillance and censoriousness with gusto. Testing fans should be careful what they wish for.

Scepticism is not the same as outright opposition, so please don’t misread this article as a rejection of large-scale testing, combined with tracking and tracing. There is a trade-off between privacy and public health associated with such an approach, but if the public health benefits are large, and if the “privacy costs” can be kept under control – it might well be worth it. More to the point, the trade-off is inescapable anyway, and the current approach is not exactly ideal from a civil liberties perspective either. So a more selective approach could be a net positive for freedom, if it means that general restrictions can be lifted. But there needs to be a frank discussion, scrutiny, and a genuine commitment to minimising the negative impact on civil liberties.