Interview: Measuring the virus' spread in Luxembourg


Rejko Krüger, pictured, says the study will provide information on the prevalence of the virus in Luxembourg 


Pierre Pailler: What information will the study provide?

Rejko Krüger: First of all, and this is very important, our study will provide information on the prevalence of the virus in Luxembourg. There are indications that the prevalence of the coronavirus is underestimated. This is due to the fact that the usual tests focus on individuals who have symptoms, without testing people who have few or no symptoms. This will provide a much more objective assessment of the extent of the spread of coronavirus in the population.

Secondly, the other information that the study will provide is how the virus spreads in the population. During a first examination, we will detect people who do not have the virus. We will keep them under observation by making a diagnosis every two weeks for two months. Some will be infected with the virus, they will develop symptoms and we will detect it.

Then, using serological tests, we will observe people who are infected but who have not yet developed immunity. These serological tests will inform us about the development of immunity once the infection is overcome. After these two months, we will do a final evaluation in a year's time to see how immunity is built and maintained over the long term.

What types of tests are performed in this study?

At the moment, there are two ways to detect whether the infection is active or has occurred. Diagnostic PCR tests look for the virus itself. They can be done with samples taken from the mouth or nose.

After some time, immunity develops and antibodies appear. And this can be observed with serological tests, blood tests.

How reliable are these serological tests?

Unlike PCR tests, which are very well established, serological tests are still under development. But we are confident that we have identified a serological test that is much more reliable and is already being used in different parts of the world. And the immunology and infectious diseases department at the LIH is still testing these tests itself so we can make up our own mind. We expect the results soon.

What is currently known about potential immunity to covid-19?

This is an important point on which, frankly, we need data. If you look at joint publications, you'll find some conflicting information. But you have to be aware that studies related to immunity have potentially been conducted using tests that are not yet perfect, hence the ambiguous results. For the time being, we hope that there is an immune response, which tests show in several studies.

But the question is: how long does this immunity last? There has been speculation that it could last from months to years. But frankly, since no one has tracked it, we don't know. And that's exactly what we want to answer with our study: if someone has antibodies now in our tests, in a year's time, we can answer that question about how long the immunity lasts.

How is the sample group of 1,500 people selected?

Our study is really a team effort. And it's very impressive because those participating are not only research or health institutes, but also private institutes, such as laboratories or TNS Ilres.

The latter allowed us to take a representative sample of the Luxembourg population. This is possible because TNS Ilres has panels of more than 18,000 individuals. A selection of the right people will be made according to age, gender, nationality and place of residence in Luxembourg, in order to constitute a representative sample of the entire Luxembourg population. They will then be contacted to join our study.

When are the different results expected?

First of all, a reference sample must be recruited. We expect the first results within the next few weeks, then every two weeks for two months. In total, we will obtain results four times. Then the results of the final evaluation in a year's time.

This project is one of several initiatives launched under the auspieces of the Luxembourg taskforce. Who are the other members?

Interactions with other projects are indeed already planned. It is a kind of two-step approach. In our study, the selected people have to fill in some basic information. But they can also be invited to join other studies without obligation.

In this way, projections can be made thanks to Professor Rudi Balling of the LCSB, with whom we work closely. The data may be useful for studies by Professor Markus Ollert of the LIH on our diagnostic testing capabilities. Or for the development of solutions in the field of e-health, such as mobile phone applications, on which Dr. Damien Dietrich is working.

Selected individuals may also choose to fill in additional data by answering questions about the state of mind, anxiety or depression that can occur in this type of situation, or questions related to socio-economic aspects.


This article was originally published on paperjam.lu on 10 April. The interview was conducted Pierre Pailler and translated by Delano.