In a cross-sectional study, the researchers of the University of Tartu ascertain the actual prevalence of the coronavirus and the progress of the epidemic in Estonia. Based on a random statistical sample, people are interviewed and tested across Estonia to give the state evidence-based data for making decisions about the measures to curb the spread of the virus. The study is financed by the Estonian government.
After each survey wave, the research team presents the government interim conclusions that form the basis for evaluating the efficacy of the anti-COVID-19 measures and amending them.
The prevalence of the coronavirus is determined among both the symptomatic and asymptomatic population. This makes it possible to estimate the state-wide spread of the virus in different population groups and regions. The prevalence study reveals the main background characteristics and risk factors of infection (e.g. underlying diseases, size of household, socioeconomic status, types of contact, etc.) and how they relate to the prevalence of the coronavirus. The long-term study helps to follow the change of the number and share of people infected over time and evaluate what factors it is related to. From February 2021, the presence of coronavirus antibodies is also determined among the adult population.
The participation in the study is voluntary; people who have become part of the sample can refuse to be interviewed and/or tested at any moment. The interviewing of the people included in the first wave began on 23 April 2020. The study will continue throughout 2021. Each survey wave lasts for one week.
Read more:Study on coronavirus prevalence launched (23.04.2020)The first results of a cross-sectional study on the prevalence of the coronavirus in Estonia (06.05.2020)A study conducted by the University of Tartu continues to show a low prevalence of the coronavirus (12.05.2020)The results of a monitoring study conducted by the University of Tartu for presentation to the government committee confirm that the easing of restrictions is justified (02.06.2020)The fourth wave of the monitoring study by the University of Tartu that was presented to the Government did not identify any positive COVID-19 cases (25.06.2020)University of Tartu researchers continue the study on the point prevalence of coronavirus (06.08.2020)The government supported the proposal of the researchers of the University of Tartu to initiate a targeted monitoring study in Ida-Viru County (27.08.2020)
„If we want to evaluate the efficacy of the measures enacted in the emergency situation and amend the decisions taken thus far in an evidence-based manner, it is important to know the data of the prevalence of the coronavirus among the population. Correct information enables us to select the correct methods."
The head of the monitoring survey,
Head of the Institute of Family Medicine and Public Health at the University of Tartu,
Professor of Family Medicine Ruth Kalda
*As the sample is stratified by region, age group and gender, the estimation of prevalence is not based on the simple arithmetic mean but the corresponding weighted mean.
*In waves 16 and 17, also post-stratification based on vaccination information was used. This means that the actual vaccination level according to the Health Board was also taken into account in calculating the weighted average.
People will be selected into the random statistical sample of the cross-sectional study based on the population register data on their gender, age and location. Men and women 18 and over will be included in the study. The study will not include people who cannot or do not wish to participate in it. The people who have been invited to participate in the study have the option of ending their participation at any moment in time.
People from 17 regions of Estonia will be included in the sample of the study: from every county and separately from Tallinn and Tartu.
The panel survey is conducted by the social and market research company AS Emor who gets the information on the people in the sample from the population register.
The people who have been included in the sample will be sent an online questionnaire and those who agree to participate in the study will fill it out. The elderly are interviewed over the phone as well, and the interviewer fills out the electronic questionnaire during this. The interviewer calls the study subject, explains the goal of the study and asks whether the person who answered is willing to participate. If the answer is negative, the interview will not be carried out. If the answer is positive, a standardised interview is used.
Both those who answer by phone and those who answer online will be asked about the manifestation of symptoms and important background characteristics, e.g. comorbidities.
Those who have answered the questionnaire will then be contacted by Medicum to arrange the time and location of the testing site where the study participant should go for testing.
The participants will get a link for registration or a call from the Medicum and Synlab testing centres to agree about the suitable time for testing at Synlab testing sites in county centres or in general hospitals. Separate testing points are set up there for those participating in the study. A PCR test from the nasopharynx will be used for testing coronavirus; this shows the existence of the virus RNA in the organism and indicates to an active infection. Antibody testing requires a venous blood sample.
It takes about 10 minutes in total to take both tests. Disabled or elderly people and people with impaired mobility may order a testing team to test them at home.
The analysis of the tests will take place at the Tallinn molecular diagnostics laboratory of SYNLAB, to which the tests will be transported twice a day. The results of the tests will be entered into the Patient Portal and the joint testing call centre of Medicum and SYNLAB will inform the test subjects of the test results.
All those that the study finds to be infected are monitored and interviewed weekly until the end of the disease. If the infected person does not become symptomatic, he or she will be interviewed within two weeks.
The study subjects can be certain that their personal data will be gathered, kept and stored confidentially.
The survey company will get the personal data of the persons in the sample from the population register. The gathering and processing of the data is organized according to the Personal Data Protection Act. The personal and health data of the participants of the study will be gathered in the course of the monitoring programme, and AS Emor and SYNLAB Estonia will forward the data to the University of Tartu in an encrypted form. Only two previously determined members of the University of Tartu research team have the right to decrypt the personal data. The data that would enable to identify a person will be separated from the health data, encoded and kept separately.
The University of Tartu research team will not forward to third persons the data that would enable to identify the participants of the study. The results of the scientific study could be forwarded to other countries for international cooperation. In that case, the data that is sent to other countries will be anonymized, taking into account the rules for protecting personal data in the relevant country.
The Research Ethics Committee of the University of Tartu has approved the study.
About 2,500 people are tested in each survey wave. Survey waves take place every few weeks. The study continues throughout 2021.
The interviewing and testing of the people in the sample, the analysis of the data and the personnel costs of the research team are about 200,000 euros per survey wave. The study is financed by the Estonian government.
- What the actual prevalence of the SARS-CoV-2 infection is among the population, in different population groups (according to age, gender, location and nationality) and among asymptomatic persons. What the number and share of infected persons is.
- What the dynamics of the SARS-CoV-2 prevalence is. How does the number and share of infected persons change over time and what are the factors connected to it.
- What are the main background characteristics and risk factors (comorbidities, size of the household, socioeconomic status, contact types etc.) connected to SARS-CoV-2. How these are connected to prevalence.
- What is the progress of the SARS-CoV-2 infection and the COVID-19 disease (recovery, symptoms, the severity of the disease, hospitalization, death) and how this is connected to the background characteristics and risk factors. Does the progress of the disease change over time.
The study is being prepared and conducted with an involvement of a broad-based collection of University of Tartu researchers, including experts from the University of Tartu Institute of Family Medicine and Public Health, Institute of Genomics, Institute of Computer Science, Institute of Mathematics and Statistics, Johan Skytte Institute of Political Studies.
Ruth Kalda (Professor of Family Medicine)
Mikk Jürisson (Research Fellow of Public Health)
Mihkel Solvak (Associate Professor of Technology Research)
Meelis Käärik (Associate Professor in Probability Theory)
Uku Raudvere (Scientific Programmer)
Anneli Uusküla (Professor of Epidemiology)
Lili Milani (Professor of Epi- and Pharmacogenomics)
Kristjan Vassil (Associate Professor of Technology Research, Vice-Rector for Research)
Krista Fischer (Professor of Mathematical Statistics,
Associate Professor of Biostatistics)
Aime Keis (Junior Lecturer in Medical Ethics)
Jaak Vilo (Professor of Bioinformatics)
Hedi Peterson (Associate Professor of Bioinformatics)
Liis Kolberg (Junior Research Fellow of Bioinformatics)
Mait Metspalu (Professor of Evolutionary Genomics)
Tuuli Jürgenson (Statistic)
Ene-Margit Tiit (professors emeritus, Faculty of Science and Technology)
More information on the survey can be reached from:
Ruth Kalda, Head of the Institute of Family Medicine and Public Health, University of Tartu, Professor of Family Medicine 58383863, ruth.kalda [ät] ut.ee
Mikk Jürisson, Associate Professor of Public Health, University of Tartu, mikk.jurisson [ät] ut.ee
Liina Veskimäe, 5838 3863, liina.veskimae [ät] ut.ee
Deniss Vendre, 53632958, deniss.vendre [ät] ut.ee (information in russian)