CON-VINCE (COvid-19 National survey for assessing VIral spread by Non-affected CarriErs) is a national project aiming to evaluate the dynamics of the spread of the COVID-19 disease within the Luxembourgish population.

“CON-VINCE” was launched in April 2020 as one of the several initiatives put in place under the aegis of the Research Luxembourg COVID-19 task force to help contain the current pandemic. By screening a statistically representative panel of volunteers for the presence of the SARS-CoV-2 virus, the study will identify asymptomatic and mildly symptomatic individuals and follow them up for a year.

Ultimately, the study aims to generate accurate data on the prevalence and transmission of the disease, assisting policy-makers in taking evidence-based decisions over the course of the coming weeks.  

Why is this research important?

Asymptomatic individuals – often referred to as “silent carriers” – and mildly symptomatic carriers play a significant role in the spread of the SARS-CoV-2 virus. However, they currently remain largely unassessed, since diagnostic testing is performed predominantly on people with clear COVID-19 symptoms. In order to put in place effective measures to stave off the COVID-19 infection, it is crucial to systematically test a representative sample of the population in order to identify all individuals carrying the SARS-CoV-2 virus, regardless of their symptoms.


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Aim and design of the research

In this context, “CON-VINCE” aims to provide reliable information on the nature, prevalence and transmission modality of COVID-19 in Luxembourg, therefore guiding national and international decision-makers in mounting an effective public health, political and economic response to the pandemic. The project will also enable the tracking of the psychological and socio-economic impact of long-term containment measures on the general population.

The study will test a panel of approximately 1,500 participants over the age of 18 and detect the three main groups of asymptomatic or mildly symptomatic people, namely:

  • individuals who are “virus-free” and therefore asymptomatic;
  • people who are currently infected but present mild or no symptoms;
  • and those who were infected but are at present free of the virus.

Participants testing positive for SARS-CoV-2 but displaying mild or no symptoms will be followed up over one year, together with virus-free individuals. Conversely, symptomatic patients will be excluded from the study and undergo regular treatment instead.

Your participation

The choice of participants in the panel needs to accurately reflect the actual composition of the Luxembourgish population in terms of age, gender and geography, in order to avoid biased and statistically inaccurate results. Therefore, LIH will not contact eligible candidates directly to participate in the study. At this stage, participation of volunteers from the general population is unfortunately not yet possible.

Frequently Asked Questions (FAQ)
  • Where can I find the subject information sheet (participant questionnaire) and my consent form?

Detailed information about your participation in our study can be found here:

Participant information questionnaire:

Consent forms:

  • What diagnostic lab sites are available to CON-VINCE participants and during what days/hours?
May I attend a different lab than the one on my voucher?

Yes, you can attend a different lab than the one on your voucher.

I can no longer attend the lab on the day I selected, what next?

Please visit the lab at your next availability with respect to the labs opening hours and opening days for CON-VINCE participants:

May I attend the lab on a Saturday?

No, the labs are currently not open to CON-VINCE participants on a Saturday.

I completed the online survey but I didn’t receive my voucher to visit the lab, how should I proceed?

Please contact us: or by phone at: +352 26970-800.

I would like to provide stool sampling, but I haven’t received any information on this, how should I proceed?

Stool kits will be provided at the diagnostic labs during sampling collection with the necessary information on how to do the sampling. If you did not receive a stool kit please contact us: or by phone at: +352 26970-800.

My TNS-Ilres link does not work, or has expired, how should I proceed?

Please contact us: or by phone at: +352 26970-800.

I have been invited for large-scale testing, should I still attend my CON-VINCE visit?

Yes, large-scale testing operates independently to the CON-VINCE study, it is important that you continue to attend your CON-VINCE appointment.

I have the opportunity to be vaccinated, should I proceed even though I’ve had positive antibodies against SARS-CoV-2?

Yes, we encourage all our participants to be vaccinated when given the opportunity. At present, there is no data available on how long a person is protected from re-infection with SARS-CoV-2. Initial data suggest that natural immunity to SARS-CoV-2 may last for about 5 months, but further studies (including CON-VINCE) are required to better understand this phenomenon. It is therefore strongly recommended to be vaccinated even if you have had COVID-19 in the past and have developed antibodies against SARS-CoV-2. Furthermore, no safety concerns have been reported regarding vaccination of people with a history of COVID-19 infection or detectable SARS-CoV-2 antibodies.

I have the opportunity to be vaccinated or have already been vaccinated should I still participate in the CON-VINCE study?

Yes, your contribution and participation in the CON-VINCE study remains important as data related to vaccination is very important for the CON-VINCE study as vaccination will impact the viral spread within the population.  

What is a longitudinal study. And why do I have to take part repeatedly?

Longitudinal study means that participants are followed repeatedly over time. While most prevalence studies around the world only offer a one-time snapshot to participants, the CON-VINCE study is unique since it has incorporated multiple follow-ups over time. This provides us (i) up to date clinical information of participants in a changing environment, (ii) repeatedly check their health status and draw conclusions on how the virus spread, immune response and/or symptoms of how the disease evolve over time. This goes beyond results from a single diagnostic approach in large-scale testing. For research, your repeated participation is particularly important as little is known about the long-term effects of the SARS-CoV-2 virus. For the success of the CON-VINCE study, it is crucial that the same participants are contributing data and biosamples every 2 weeks over the course of 2 months and then once more after 1 year for assessing long-term developments.

Which tests are done as part of the study?

Besides filling in different questionnaires, participants will undergo 2 different types of tests:
• The PCR tests aim to detect the presence of the SARS-CoV-2 virus. A positive result means that a person currently carries the virus. This is done based on a nasopharyngeal swab.
• The serology test aims to detect the presence of antibodies against the SARS-CoV-2 virus. A positive test result means that you may have been in contact with the novel Coronavirus and your body may have developed an immune reaction.

How reliable is the PCR-test to detect the presence of the SARS-CoV-2 virus?

The CON-VINCE study uses the Seegene Allplex nCoV-2019 qPCR as primary tests for this purpose, which identifies viral genomic material in the nasal-pharyngal swab. In addition, generic qPCR tests, which are based on recommendations of the WHO or the Centers for Disease Control (CDC), and the Fast Track Diagnostics qPCR test are used as confirmation tests in the CON-VINCE study. The sensitivity for this primary test, i.e., the ability of the test to correctly identify virus-positive samples (true positive rate), is 100% (according to under optimized laboratory conditions. The test specificity, i.e., the ability of the test to correctly identify virus-negative samples (true negative rate), is also 100% (according to ) under optimized laboratory conditions.

In the real world, outside a study like CON-VINCE, testing conditions and processes are far from perfect, and accuracy suffers. Researchers still don’t know what the real-world false positive rate is, but the clinical sensitivity of RT-PCR tests ranges from 66% to 80% ( That means between one in three and one in five infected people who are tested will receive false-negative results under real-world conditions.

How reliable is the serology test to identify antibodies against SARS-CoV-2?

The CON-VINCE study uses the Euroimmun Anti-SARS-CoV-2 Elisa (IgG and IgA) tests for this purpose. IgA and IgG are two different classes of antibodies that are produced at different stages of the immune response.
The test ‘sensitivity’ is defined as the ability of a test to correctly identify those with the disease (true positive rate). The supplier states that the sensitivity of the test improves with increased time after infection and when considering the combined results of both IgA and IgG antibodies against SARS-CoV-2: For samples taken >10 days after infection, in which both IgA and IgG antibodies are considered, a sensitivity of 100% can be achieved.
The test ‘specificity’ is defined as the ability of a test to correctly identify those without the disease (true negative rate). The supplier states that the Anti-SARS-CoV-2 Elisa (IgG) yields a specificity of 98,5%, while the Anti-SARS-CoV-2 Elisa (IgA) yields a specificity of 92,5%. For details, please consider the manual issued by the supplier.
A scientific publication ( recently reported a detailed examination of the Euroimmun test used in the CON-VINCE study. It demonstrated that the results obtained by the IgG kits were highly reliable and reproducible.

I would like to join the study. Is it still possible to participate now in the CON-VINCE study?

Unfortunately, at that stage of the CON-VINCE project, no additional participants will be recruited.

How representative is the panel used to recruit the CON-VINCE study cohort?

When designing the study of each research study, different criteria with different priorities need to be weighed up and met as best as possible. Our study focuses on the criteria of age, gender, and residence. Other factors such as level of education, social status, lifestyle habits, etc. could not be taken into account in the time, organizational and financial framework of the CON-VINCE study. Taking further criteria into account would, e.g., result in a significantly larger number of participants required to be able to make statistical statements for each subgroup.

Can one distinguish if I have antibodies because of a previous infection vs vaccination?

Yes, this is possible. When you have an infection, your body produces many different antibodies against different parts of the virus (e.g. the spike protein, other capsid proteins etc). In contrast, all currently available COVID vaccines only include the instructions for the spike protein (the binding part of the virus). After vaccination, your body defends you from the virus by recognising this single protein and hence preventing the entry of the virus. Depending on the antibody test used, one can distinguish the different types of antibodies and could therefore tell the origin of a person’s immune response.

In the CON-VINCE study, we will at first look for antibodies against the spike protein, which could come from either infection or vaccination, as the primary goal of the CON-VINCE study is to define the seroprevalence (presence of antibodies within a population) against SARS-CoV-2. At a later stage, we aim to apply also the more complex serology tests that allow a distinction between natural infection and vaccination.

If you still have a question, please contact us by email at: or by phone at: +352 26970-800

A. I am a participant in the CON-VINCE study
Will the CON-VINCE study team communicate the results of the PCR test?

In cases of virus-positive results, one of our medical doctors will contact you within 48 to 72h after sample collection to explain the result. If you don’t hear from us within this time frame, you do not currently carry the SARS-CoV-2 virus.

Will the CON-VINCE study team communicate the results of antibody (serology) tests?

Positive results from antibody testing will be communicated, within 2 weeks after the final participant has been sampled at the end of May 2021.

Why does the CON-VINCE study team not communicate all results?

Participant identifiers are removed for clinical research, and re-identification is only completed in exceptional circumstances to notify participants of a positive test result.

I had a positive antibody test. What does this mean for my immune status?

It is important to understand that the presence of antibodies in your blood, even if clearly against SARS-CoV2, does not necessarily mean that you are immune as some people have tested positive for the virus more than once. Further research is needed to better understand if and for how long antibodies protect against the virus. Furthermore, it is not known whether you could transmit the virus even though you have developed antibodies. Therefore, you need to stick to the precaution measures (e.g., 2m distance, frequent hand washing, masks, etc.) recommended by the Luxembourgish government (

Should my family members get tested for antibodies if I tested positive in serology?

No, your family currently does not need to get serology tested, as currently only a positive PCR test is used to identify active SARS-CoV-2 infections.

In what cases will be my treating physician be informed?

Whenever there is a new positive result, your treating physician (if you have provided this information) will be informed.

Do I have to see my treating physician when receiving a positive antibody (serology) test result?

No, this information currently has no direct implication. Also, it is still not known whether a positive antibody status indicates immunity. If this should become relevant due to additional information obtained during the CON-VINCE analyses, we will get in touch with you. Please keep following the general safety measures (social distancing, masks, hand-washing, etc.) communicated by the government.

What happens to my data?

Your personal data is collected and analysed to achieve the scientific objectives of the study (analysis of epidemiological, socio-economic and psychological aspects of the confinement during the pandemic). We ensure the protection of your data in accordance with the General Data Protection Regulation (EU) 2016/679 of 27 April 2016, applicable as of 25 May 2018, known as the “GDPR”. Detailed information about data processing can be found in the information questionnaire. If you have questions concerning the processing of your personal data by the LIH or LCSB/UL, you can contact the Data Protection Officer by e-mail at or

Why should I contribute with stool samples to the CON-VINCE study?

The gut microbiota is crucial for the immune system function, helping to keep harmful pathogens away. The SARS-CoV-2 virus has been found in stool samples of infected individuals with or without respiratory symptoms. Studies* indicate that the stool samples may be positive for the virus even after the naso-pharyngeal swabs turned negative. The gut microbiota could influence the outcome of COVID-19 disease. SARS-CoV-2 virus and variants can be detected via sequencing from fecal samples*.

I am back at work; how can I still make sure to contribute to the important biosampling?

Please try to visit the chosen laboratory on the assigned date. This helps us to better estimate the workload and adapt the capacities of the laboratories accordingly. If this should not be possible, you can choose to go to any other laboratory on the list (at the top of this page) within the same week or contact us.

Can I go to another lab or plan for the sample collection at home with the same voucher?

Yes, your voucher is valid for the whole recruitment wave and all laboratories on the list, including collection at home.

Can I get a certificate for work?

Yes, please simply ask for it by sending an email to Please indicate in this email the sampling site you visited and your COV number.

B. I am a treating physician
Why do I receive results?

Within the CON-VINCE study, the clinical study team communicates virus- or serology-positive results to both the patients as well as his indicated treating physician. This is particularly relevant for virus-positive results, where clinical care may be necessary.

My patient has a positive or inconclusive PCR test result. Do I have to undertake any further diagnostic steps?

We take care of a confirmatory diagnostic test in case of a positive result, and you will obtain a copy of the diagnostic test result. If your patient is positive, he/she will need to follow the isolation guidelines as foreseen by the Ministry of Health.

My patient has a positive IgA/IgG antibody test result. Do I have to undertake any further diagnostic steps?

In the case of positive IgA or IgG antibody, currently, no further tests are needed. This is just to inform you that your patient was previously in contact with the virus.

Will I only be informed about positive results?

Yes. We do not contact the treating physician in case of negative results.


The “CON-VINCE” study is led by a consortium of Luxembourgish research institutions, including:

The study is supported by the market research company TNS-ILRES for the selection of participants and of the laboratories Ketterthill, Laboratoires Réunis, BioneXt Lab, as well as of LIH and Laboratoire National de Santé (LNS) as associated partners for biospecimen collection. The study is co-funded by the Luxembourg National Research Fund (FNR) with an amount of EUR 1.4 million and by the Fondation André Losch through a financial commitment of EUR 800,000.

“CON-VINCE” is implemented under the aegis of the Research Luxembourg COVID-19 task force.

Research Luxembourg is a joint initiative of the main players in Luxembourg public research Luxembourg Institute of Health (LIH); Luxembourg Institute of Socio-Economic Research (LISER); Luxembourg Institute of Science and Technology (LIST); Laboratoire National de santé (LNS); University of Luxembourg; Fonds National de la Recherche (FNR), supported by the Ministry of Higher Education and Research. The main aim of the initiative is to promote scientific cooperation in Luxembourg and to communicate the activities of the sector as a whole.



Prof Rejko Krüger:


Arnaud d’Agostini:

Hélène Jacuszin: