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José Lamas |
11 Min.

Social Vaccine: Exposure Notifications in Coronavirus UY

The application uses Google and Apple’s Exposure Notifications API and cleverly solves complex technology, security and privacy issues. It gives us a great opportunity but to take advantage of it, as with optical illusions, we need to be able to see beyond our first impression.

Achilles the light-footed

At this point in the fight against COVID-19, our speed of reaction is the key factor. For every new case that is detected, we need to quickly identify those who have recently been in contact with that person to check if they have also become infected. This has a double benefit: it ensures prompt medical assistance to those who have the disease and also minimizes the number of new transmissions through isolation measures. 

In a recent interview with the news publication La Diaria, members of the Uruguayan Interdisciplinary Group for Data Analysis of COVID-19 (GUIAD by its acronym in Spanish) highlighted Uruguay’s capacity to follow up contacts as the main explanation for its good performance in the fight against the disease, but also as its Achilles’ heel in facing the challenges ahead.

The reason is that as long as the number of cases remains relatively low, it will be possible to carry out this personalized contact tracing, checking with those involved in each case and directly contacting each person identified by them.

Successful control of the recent outbreak in the department of Rivera is a clear example. From the first local case detected on May 7, the numbers grew rapidly: by May 26 the number of active cases reached 29, and by June 2 it reached a peak of 48; at that time it was the department with the most active cases in the country. The fast identification of new infections, as well as their care and isolation, were key to controlling this outbreak and prevented it from spreading to other parts of the country. By June 29, Rivera managed to return to zero active cases.

However, in the event of larger outbreaks (that of the department of Treinta y Tres reached a peak of 69 active cases on July 3), or multiple simultaneous outbreaks (such as those that seem to be occurring these days in Montevideo), it will be very difficult to achieve the same results. Nicolás Wschebor, from the Physics Institute of the School of Engineering and a member of the Interdisciplinary Group, warned about this at the interview mentioned above. “This case tracking measure that is extremely valuable and is one of the reasons for Uruguay’s success has, on the other hand, a very low operating threshold: with only a few more cases, the situation can no longer be controlled,” said Wschebor.

Antonios, Beatrices and Johns

The Exposure Notifications recently incorporated into the Coronavirus UY app can be a key ally because they allow identifying and alerting others possibly infected in an early, efficient, and fully automatic manner.

The results are similar to the contact tracing that the staff of the Ministry of Public Health has been conducting “manually” from the onset of the crisis, with the advantage that it covers many more cases, since it does not depend on people knowing each other or remembering that they were together and being able to provide contact information. Being an automatic process, it is also much faster and does not experience overload problems if the number of cases increases.

For example, if Antonio receives a positive test result, other people who have recently been around him may get an automatic alert on their phone about possible exposure to the virus. Maybe Antonio doesn’t know Beatriz, but if a few days ago they were near each other while waiting for the bus, she can now receive an alert from his phone and then consult her doctor, who can indicate a test to confirm or rule out contagion.

If Beatriz was infected that day, the automatic alert on her phone would allow her to become aware of it and receive medical attention much earlier and therefore much more effectively than if she had to wait until experiencing the first symptoms, which may not even appear. In addition, although perhaps she has already infected Carlos, he will still be able to take precautions that will prevent him from infecting John, which in turn will prevent Daniela, Diana, and Dolores from being infected, who will then not be able to infect Eduardo, Enrique, Ernesto, Esteban, etc.

Multiplying this by the thousands of Antonios, Beatrices and Johns can give an idea of the importance of these automatic alerts. Although receiving an alert a few days earlier may seem irrelevant, receiving it in every case and at every possible stage in the chain of contagion can be the key to avoid an uncontrolled spread of the virus.


On the street, being together while staying apart

Around the world, the main tool for fighting the disease has been physical distancing. Even though this and other measures have been successful in many cases, some countries have had to backtrack on reopening due to major resurges when restrictions were removed or relaxed. 

Exposure Notifications can be very useful in addressing precisely that risk. Increasing the scope and speed of our response can be a great help to face the gradual reopening of our economy without losing control over the disease that we have worked so hard to achieve.

If we have this great tool at hand, what prevents us from taking advantage of it? The first challenge has to do with early action. If Beatriz waits until she has the first symptoms of the disease, enabling the alerts at that time will no longer work; the chance she had of receiving an early warning has already been lost.

The next challenge is one of coordination: in order for Beatriz to receive an alert, it is not enough for her alone to activate the system. Potential Antonios need to do so as well.

In broad terms, the effectiveness of the system depends on how much of the population uses it. According to an article published by the University of Oxford, it has been said that a 60% adoption rate would be necessary, but this was a misinterpretation of its results. 

Andrea Stewart, a spokeswoman for the Oxford team, stated that “there’s been a lot of misreporting around efficacy and uptake… suggesting that the app only works at 60% – which is not the case.” Actually, even with lower adoption levels there still would be beneficial outcomes.

In addition, even if it is not possible to achieve high levels of usage among the total population of a country, if it is achieved for certain groups or smaller ecosystems there will be positive effects that, although not general, will be valid for them.

For each person, the probability of receiving an alert does not really depend on the rate of adoption in the country as a whole, but on the rate of adoption among those people he or she may be in contact with.

This is the reason why many companies, educational institutions, or social organizations have promoted the use of the application among their members; recently, the authorities of the Uruguayan Football Association have even considered making its use mandatory.

Achieving adequate adoption in a given group is enough to achieve results within that group, and focusing initially on each of those groups may be the way to achieve significant adoption at the general level as well.

Anyway, it is clear that if it takes two to dance a tango, in this particular case we need to be more, much more than two.

I don’t care in what way or where or how

What is new tends to cause doubts, and this uncertainty can paralyze us. Although all the information about the system is available, from the most technical details about design or implementation to detailed explanations that allow us to understand how and why it works in a way that protects privacy, many still have doubts or lack information, and because of that they still don’t use it. 

To make things even more difficult, the system works in ways that do not match our intuition. To meet freedom and privacy requirements, ingenious mechanisms are used and even though they are simple –precisely because they are new– they can be a little disorienting.

For example, when we think of contact tracing, the first solution we usually think of is to record where each person moves. If we know where everyone was at every moment, it would be easy for us to find out who was in the same place at the same time, wouldn’t it?

Actually, is it not necessary to know where people have been, but only if they have been close to someone who could transmit the virus. The system does not use any geographic information. It does not query, report or record where each person has been; it does not need to.

Don’t tell me who you hang out with

Having clarified the above, if we think of determining whether someone has been near someone else, the first thing that comes to mind is to identify and record who was near whom. With that information, once it is known that Antonio’s test was positive, it would be trivial to know that it is Beatriz the one who could have been infected…

It is also unnecessary to know who Beatriz was close to, but only if she was close to someone who had the virus. To solve this, instead of using people’s names or identifiers, the app uses randomly generated numbers that cannot be associated with people. Phones send out these codes and record the ones they receive from others.

If at some point it could be determined that Beatriz’s cell phone has received a code issued by someone else’s phone who later tested positive, it would be enough to determine that Beatriz was exposed to the virus, even if we don’t know who she’s been in contact with and we can’t tell her who it is. 

No way leads to Rome

We have already cleared up some doubts, but there are still other aspects about which our intuition can lead us astray. 

When it comes to phones we tend to think of messages going through an intermediary, like when we send an SMS or WhatsApp message, but actually these codes are sent via Bluetooth. This means that communication takes place directly between nearby devices and doesn’t go through phone operators, application servers, Apple or Google.

Also, when we think of a notification system, we tend to assume that someone sends them. For example, a system that recorded the codes issued and received by each phone could then identify Beatriz as having been exposed and send her a notification accordingly.

In fact, this is how centralized contact tracing systems work, such as those implemented by some countries (e.g. France and, initially, the United Kingdom). Even though they are also based on the use of Bluetooth, they centralize contact tracing and notification delivery.

In contrast, in the Exposure Notifications system implemented by Apple and Google, which is the one used by the Coronavirus UY application, not only information storage is decentralized but also contact detection.

The information of the codes sent and received is stored in each phone only. When a person is diagnosed as having the virus, he or she will be asked for permission to share what his or her cell phone has issued, and the phones involved, like Beatriz’s, will periodically receive what is shared by all those like Antonio who have tested positive and agreed to collaborate. 

Upon receiving these codes, Beatriz’s phone is the only one that can find a match and this is only reported to her. It’s not that Beatriz gets a message from someone; her cell phone issues the alert, so it’s more like an alarm clock than an SMS message.

Social vaccine

Our immune system relies on the interaction of multiple components (such as lymphocytes and antibodies), and as a result the body is able to detect the presence of harmful agents and trigger a response. Vaccines stimulate this system and enable it to recognize and effectively fight the agents that cause specific diseases, such as smallpox or measles.

Intensive work is underway in various parts of the world to develop a vaccine against COVID-19, and while encouraging results have already been achieved, including recent announcements by the Jenner Institute at Oxford University, we could be months –or even years– away from having a fully tested vaccine available to everyone. 

In the meantime, what we can’t do is sit around and wait. Exposure Notifications are the social equivalent of a vaccine because they allow us to be better prepared to detect the presence of the virus at multiple locations, and provide a coordinated response capable of effectively controlling it.

This vaccine already is available, and it can be applied with just a few clicks. Let’s hope we don’t miss out.


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