‚ÄčThe Dutch Minister of Health, Welfare and Sport Hugo de Jonge announced today that CoronaMelder should be available to everyone by September 1. Carl Moons, Professor of Clinical Epidemiology at the UMC Utrecht, supports this app “because we combine it with direct access to testing. That is absolutely imperative.”

Carl Moons is chairperson of the supervisory committee that advises the Minister on digital aids in the fight against corona. “This app can definitely help in tracing contacts of infected persons and so prevent more coronavirus infections.”

The app, which is not linked to persons or names, works as follows. If two people have installed the app on their mobile phones and have been in close proximity (within one and a half meters) to each other for a longer period of time (at least ten minutes), the apps on the two mobile phones are connected. If one of them later appears to have Covid-19 as confirmed by a positive test, the second person receives an alert in the app that she or he has recently been in the close vicinity of an infected person (a so-called high-risk encounter). The second person can get her- or himself immediately tested, guided by the exact day of this high-risk encounter.

Testing twice
“For the apps that were discussed in April and May, the idea still was that people who received an alert would immediately self-isolate for fourteen days. The supervisory committee did not find this acceptable, as it would have too great an impact on citizens, society and the economy. The supervisory committee’s advice is therefore that is one receives an alert in the app – the person must have access to a testing facility as soon as possible, guided by the day of the encounter” says Carl. “For example, if that high-risk encounter was the day before testing may be indicated after two days, and if the encounter was three or more days ago access to testing must be immediately possible. Which days to test is currently being investigated”.

His committee argues that you should not only be able to get tested just once, but twice. “research indicated that on average you develop symptoms around day four or five after being infected. Research also indicated that one can be contagious after three or four days after infection. So quick testing is important. It is also known that the first test is incorrectly (false) negative because there are still too few virus particles in the nose. If after a first negative test, you get tested again, for example three or four days later and you are negative again, experts say that you can be fairly certain that currently you’re not infected.” There is now sufficient testing capacity available in the Netherlands.

The more the better
When asked how many people have to install the app before it is effective, Carl is clear: the more the better. “In the spring, it was mentioned several times that an app is only effective when sixty percent of people use it. That’s a myth. Even the University of Oxford, where that figure comes from, says it has been misinterpreted. If a country does not have any other preventive strategies – such as traditional (analogue) contact tracing and social distancing - then sixty percent app use is required to effectively address the pandemic. If you do have other preventive strategies in place, even a low percentage may prevent infections and so already has an effect. But obviously: the more people install the app, the greater the effect.”

The exact effect on virus spread and public health will of course not become clear until the app is actually used. “Now the app has only been investigated in a small group with simulated infections. Of course, we normally would like to investigate innovations and apps like this further before wide scale implementation. But we simply don’t have that time now. The virus is too fast, and we see already here and there rising infection rates. We have to do these empirical effectiveness evaluations while implementing the app. A living healthcare system.”

Personal benefit
He will also install the app himself. “Some say they do it out of civic duty, to protect others. That’s certainly also true, but you may also benefit personally. In combination with up to two subsequent tests as indicated by the day of the high-risk encounter, you know with high certainty whether you are infected or not. In the latter case, you can may hug your partner, children or parent.”