CON-VINCE, a national research project aiming to evaluate the prevalence and dynamics of the spread of COVID-19 within the Luxembourgish population, was launched at the beginning of April under the umbrella of the Research Luxembourg COVID-19 Task Force. The second round of testing of the participants in the study (first follow-up after baseline testing) showed a declining infection rate and lower prevalence of the disease, while bringing forward the risk associated with asymptomatic individuals in the context of a second COVID-19 wave.

Declining infection rates

Following the first baseline screening of all participants between mid-April and May 2nd, a second testing exercise took place from May 4th to May 16th as a first follow-up. As part of this phase, all participants were subjected to a second nasal and oropharyngeal swab, followed by a PCR-based analysis to detect the presence of the SARS-CoV-2 virus. During this period, 2 participants out of the entire panel tested positive for the virus, i.e. 0.1%, compared to 0.3% for the first testing round, reporting only mild symptoms. This translates into an estimated 402 infected but asymptomatic or oligosymptomatic (with only mild symptoms) individuals in the Luxembourg population, excluding cross-border workers. “Despite the declining prevalence of the infection, it is important to point out that all the SARS-CoV-2 positive participants in our panel displayed mild or no symptoms and are therefore ‘silent carriers’. This means that they could potentially start new infection chains without knowing it”, explains Prof Rejko Krüger, principal investigator of the CON-VINCE study.

Increasing antibody presence

A serological test was also carried out to detect the presence of antibodies in the blood, which may be an indication of past exposure to the virus. The results showed that 38 participants (2.6%) had antibodies against SARS-CoV-2, compared to 2.09% during the first round of screening. “We noticed an increase in the proportion of participants with antibodies against the virus, although I stress again that the presence of antibodies does not mean that people are immune to COVID-19”, adds Prof Krüger.

Encouraging participation rate

The participation in the study has also shown positive results, with over 94% of participants of the first testing phase having enrolled for the follow-up round. “We would like to extend our gratitude to all volunteers who renewed their participation in our study. Without their continued motivation and commitment, we would not be able to generate meaningful data and research outcomes for patients and the population in general”, says Prof Krüger. “To keep encouraging enrolment in the upcoming follow-up tests as participants progressively return to work, we will make it possible for them to obtain a certificate of participation in CON-VINCE upon request at the laboratories”, he concludes.

CON-VINCE – more than just infection and serology

In addition to generating data on SARS-CoV-2 infection, CON-VINCE allows participants to make additional key contributions to a variety of related research questions in the context of the COVID-19 pandemic. Namely, the information collected during the study will help answer questions on mental wellbeing, immune response and immunity, infection pathways, the role of the gut microbiome, genetic predisposition and the socio-economic impact of COVID-19. Indeed, CON-VINCE differs from the newly-launched large scale testing (LST) initiative in that it does not aim to simply give a snapshot of the infection status at the time of testing. On the contrary, participants choosing to get tested in the framework of CON-VINCE provide their biological samples for research purposes, in order to support additional studies. For instance, although not compulsory, CON-VINCE participants are strongly encouraged to donate stool samples since SARS-CoV-2 can also be detected through the analysis of faeces. These samples can then be used to perform further analyses as part of other research projects (e.g. detection of the virus in wastewater and elucidation of the role of the gut microbiome composition in determining different susceptibilities to COVID-19).

A multidisciplinary consortium

The success of the project relies on the multidisciplinary expertise of its consortium partners, each implicated in different aspects of the multifaceted study. Specifically, the Luxembourg Institute of Health (LIH), the Centre Hospitalier de Luxembourg (CHL), the University of Luxembourg with its Luxembourg Centre of Systems Biomedicine (LCSB), the Luxembourg Institute of Socio-Economic Research (LISER), the Laboratoire National de Santé (LNS) and the Luxembourg Institute of Science and Technology (LIST) contributed to the establishment of the study protocol and setup of the case report form (CRF). TNS Ilres, Laboratoires Réunis, BioneXtLAB and Ketterthill are involved in recruitment and data collection. The LCSB and LIH are involved in data integration and storage. Laboratoires Réunis, BioneXtLAB and Ketterthill are responsible for sample collection, while the Integrated Biobank of Luxembourg (IBBL) ensures sample processing and storage. CON-VINCE is financially supported by the Luxembourg National Research Fund (FNR) and the André Losch Foundation.