The first round of the PIENTER Corona Study was in April and May 2020. In total, more than 3,200 blood samples were examined in this round of the PIENTER Corona Study. In the second round, in June and July 2020, RIVMNational Institute for Public Health and the Environment examined more than 7,300 samples. In both rounds of research, slightly more than half of the blood samples came from women. The invitations for the third round were sent in the third week of September. The results are expected in November.
Age distribution of participants
In general, slightly more older participants participated than younger ones. In the first round, the average age of participants was 40 years. The youngest participant was 2 years old and the oldest participant was 90 years old.
The average age of participants in the second round was 45 years. In this round, the youngest participant was 1 year old, and the oldest participant was 90 years old. The figures below show the age distribution of the participants in the two rounds of research. The age group of 35-44 years old was the largest in the first round. In the second round, the age groups of 55-64 years and 65-74 years were the largest.
Figure 1: Age distribution of participants (round 1).
Figure 2: Age distribution of participants (round 2).
Number of participants per municipality
The figures below show the number of blood samples examined for the various municipalities in the Netherlands. The distribution of blood samples for each municipality shows some correlation to the population distribution in the Netherlands: more people from the Randstad conurbation took part in the study. The research results are analysed with due consideration of differences in the participants’ gender, age, region and ethnic background.
Figure 3: Number of participants per municipality based on blood samples examined (round 1).
Figure 4: Number of participants per municipality based on blood samples examined (round 2).
People who have antibodies
The research results show what percentage of the general population in the Netherlands has had the novel coronavirus (SARS-CoV-2) and has generated antibodies against the virus. This is known as seroprevalence. During the first round of research in the spring of 2020, this was just under 3%. In the second round in the summer, it rose to 4%. In both rounds, the percentage was about the same between men and women, and also between people from different ethnic backgrounds.
Age distribution of people who have antibodies
The figures below show the percentage of participants with antibodies distributed across the age groups in the population (from young children up to 90 years old) for the first and second rounds of research. The data from the rounds of research is then converted for extrapolation and applied to the general population. An estimate is provided for the percentage of the Dutch population that has been in contact with the coronavirus in each age group.
The blue lines give an estimate per age group of the percentage of people in the Dutch population who have generated antibodies against the virus. The grey area around the blue line is the margin of uncertainty, showing the range in which the exact percentage is located.
In both rounds of research, young adults had antibodies most frequently. In the first round, 4 to 5% of people between 20 and 35 years old had had the virus. In the second round, this percentage increased to about 10%, especially among young adults in their early 20s. Among children of primary school age, the percentage still remains very low.
Figure 5: Percentage of participants who have antibodies, by age (round 1).
Figure 6: Percentage of participants who have antibodies, by age (round 2).
Regional distribution of people who have antibodies
The study also looks at the spread of the virus throughout the Netherlands. The figure below shows the percentage of participants per GGD region that had already had the virus. These are the results from the second round of research. A lighter colour (light orange) means a lower percentage per region on average, while a darker colour (dark red) means a higher percentage per region on average (up to 16%). These results clearly show that the prevalence of antibodies in the north is lower than in the central regions, and much lower compared to the south of the Netherlands. This conclusion is in line with the trends in hospitalisations and deaths due to COVID-19 in these regions during the first wave of infections.
Figure 7: Percentage of participants who have antibodies, by GGD region (round 2).
Most people who are infected with the novel coronavirus will generate antibodies. A person who has already had COVID-19 is likely immune to the novel coronavirus for some time. Exactly how long that protection will last is not yet clear. However, the more people are immune to the virus, the less the virus will be able to spread. When a community is immune to a virus, this is referred to as herd immunity. Based on the results so far, herd immunity will not be achieved in the Netherlands for SARS-CoV-2. See this scientific article.[LD1] People will also produce antibodies when they are vaccinated against the coronavirus, once the vaccine is available.
In each round of research, the participants filled in a questionnaire about their symptoms. The table below shows the percentage of participants in round 1 who had each symptom. The participants were divided into two groups. There were participants who had antibodies for the coronavirus in their blood at that time. They had been in contact with the coronavirus and were seropositive. There were also participants who had no antibodies in their blood at that time, who most likely had not been in contact with the coronavirus. They were seronegative. The results of the second round of research have not yet been taken in to account.
The seropositives had more symptoms than the participants without antibodies. The symptoms reported most frequently among seropositive people were headache, coughing, runny nose, joint pain and loss of smell and/or taste. Loss of smell and/or taste was the most characteristic symptom for participants who had been in contact with the coronavirus. This symptom showed the largest difference between seropositive participants (52.7%) and seronegative participants (3.6%). In other words, loss of smell and taste a very specific symptom that is indicative of the coronavirus.
Table 1: Percentage of symptoms reported by seropositive and seronegative participants in round 1.
|Loss of smell and/or taste||52,7%||3,6%||4,8%|
|Irritability / confusion||23,0%||7,6%||7,9%|
|Shortness of breath||17,5%||8,2%||8,4%|
|Nausea / vomiting||17,6%||6,7%||7,0%|
The results of the PIENTER Corona Study will be presented in scientific articles for publication, so they can be read by everyone. As a result, other countries can also benefit from the research and use key findings in formulating their public health policies. When articles are published online, they will be posted on this page.
RIVM has published an article on the scientific background of the PIENTER study in BMC Infectious Diseases.
Verberk, J.D.M., Vos , R.A., Mollema, L. et al. Third national biobank for population-based seroprevalence studies in the Netherlands, including the Caribbean Netherlands. BMC Infect Dis 19, 470 (2019).
An article has also been published on the laboratory method for measuring antibodies against SARS-CoV-2.
Gerco den Hartog,, Rutger M. Schepp, Marjan Kujer, Corine GeurtsvanKessel, Josine van Beek, Nynke Rots, Marion P. G. Koopmans,Fiona R. M. van der Klis, and Robert S. van Binnendijk. SARS-CoV-2–specific antibody detection for seroepidemiology: a multiplex analysis approach accounting for accurate seroprevalence. J Infect Dis. 2020 Aug 8:jiaa479.