How rapid testing could help us emerge from the pandemic

On Tuesday 9 November 2021, French President Emmanuel Macron addressed the nation on prime-time TV. Although he was roundly criticised for cynical electioneering in advance of next year’s general election (and in truth, it did resemble a party-political broadcast in places), there is also a far more prosaic explanation for this intervention – one we have become accustomed to over the last 18 months – France is about to enter the fifth wave of the Covid-19 pandemic.

As the majority of the French population now has some form of immunity to the SARS-CoV-2 virus, this latest wave is likely to be far less deadly than previous ones. However, the warning signs are visible in several neighbouring countries, and there is every reason to expect that France will follow a similar trend in the coming weeks.

It is now clear that the vaccines do not entirely eliminate the risk of catching and spreading the disease, and with waning immunity and the approaching winter (and the other seasonal diseases it brings), Covid still represents a risk in terms of hospital capacity and excess mortality over the winter. If models show that hospitals are likely to become saturated, governments may well instigate new lockdown measures, which would have dramatic social and economic consequences, as well as undermining confidence in public health measures.

One of the ways to avoid this dire projection is through a booster vaccine, which Macron was keen to encourage over 65s to get. However, as previously mentioned, vaccination alone does not eliminate transmission, and with the general population having returned to almost “normal” levels of socialisation (although mask wearing is still the norm on public transport and in other indoor public places in France, unlike many other countries) other measures are needed to prevent more needless death and chaos over the winter.

One such measure is rapid antigen testing. Although the antigen test was long portrayed as the PCR test’s poor relation, it is now apparent that it has two major advantages over the PCR test: first, it is much cheaper, and second, it is actually very good at measuring what we care about, i.e., whether the person being tested is actually contagious. When I get tested, I want to know whether I am likely to infect other people, so that I can change my behaviour accordingly. The PCR test can detect minute quantities of virus in a sample, but a person with trace amounts of viral RNA in their nasal cavity is not necessarily contagious (nor indeed infected). As a result, over the last 18 months, millions of people have been isolating despite no longer representing a risk to anyone – at a huge cost to society.

Most people thankfully now feel safe because they are vaccinated. Moreover, because they were explicitly told that getting vaccinated would enable us to return to normal, and because of the cost and hassle (on top of the fact that the entire experience is pretty unpleasant) many people simply do not get tested at the first sign of symptoms, meaning that a certain proportion of contagious people are going undetected. In addition, those who do get tested may not get the results for several days, giving them ample time infect other people. The primacy of PCR tests may have been justified earlier in the pandemic, when we lacked reliable data and we simply needed to stop community spread by any means necessary, but no longer.

American Doctor Michael Mina was one of the earliest and loudest voices advocating for rapid antigen testing as a third way, but he was confronted by the reticence of the American legislator in approving these tests. European authorities were initially similarly squeamish about this approach, but they now see antigen tests as a complementary tool in the arsenal of non-pharmaceutical interventions (NPIs). In the UK, you can order them for free, and in France they are now available at a cost that is negligible compared to the PCR (between €3.70 and €5.20 per test).

However, rapid antigen testing has not yet entered the zeitgeist as a public health measure. Mina argues that this technology should be used in a more systematic manner similar to masking: if everyone had a box of antigen tests at home, then they could test themselves preventively every time they feel under the weather or if they are going to a restaurant or a family gathering. If incidence rates are high in their area, people could test themselves preventively once a week. Saliva tests even exist as an option for parents who might hesitate to use a nasal swab on their child.

The most sensitive test in the world is useless if people don’t want to use it. Self-administered tests that provide actionable results within 15 minutes are more convenient, meaning that people are more likely to get them. This approach empowers individuals to become actors in a public health crisis, and governments should actively encourage their use in this way by saying so explicitly and providing them free of charge on demand where necessary.

Another lockdown would be hugely damaging, but it should not be necessary. We do not need to get to zero Covid – Australia has shown us that this is not a realistic objective anyway – we just need to ensure that the R=0 is below 1 by reducing community spread through preventing testing and other NPIs. The levels of vaccination in most European countries means that Covid deaths are likely to remain relatively low for now, and the news about imminent Covid treatments is reassuring, but high levels of circulation in a vaccinated population also increases the likelihood of a mutation that would allow the virus to evade existing vaccines, which is a scary prospect that we should all want to avoid.