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Number of blood donors and health workers with coronavirus antibodies remains stable

18-09-20

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Antibody level in tested blood donors hovering at 5%

Since 30 March, Sciensano, the Red Cross and le Service du Sang de la Croix-Rouge, have been investigating the levels of coronavirus antibodies in Belgian blood donors. This provides a cautious indication of the evolution of the population’s exposure to the virus.

10,453 samples were examined, and the most recent analyses show that about 5% of blood donors have built up detectable antibodies against the virus. This proportion has remained stable since April .

In our calculations, we adjusted the number of donors of the different age groups, the proportion of men and women and the province they are from to the actual composition of the population.

However, we should be cautious when interpreting these results. Blood donors (18-75 years) are a specific group within the population because they are healthy at the time of blood collection.

Percentage of antibodies in Hospital health workers remains stable at 8%

A study on the evolution of antibodies against coronavirus in health professionals in Belgian hospitals was also carried out. Sciensano and the Institute of Tropical Medicine in Antwerp have monitored a group of 850 health professionals since the end of April. The proportion of those with antibodies against the virus remained stable at 8%, showing no significant change over the study period.

5 (6%) of the 81 participants with antibodies to SARS-CoV-2 during the study, presented no symptoms.

Only 2 participants no longer had antibodies over time, i.e. about two and a half months after the suspected infection date and their only symptom seemed to be headaches.

The research among health professionals continues until the end of April 2021 and will monitor, among other things, the presence of antibodies in blood, and try to acquire more extensive knowledge about their potential protective role.

What can we conclude from these studies?

Both studies show that the percentage of people with coronavirus antibodies in the blood is well below the approximate 70% needed to achieve herd immunity, both in the 'general' population and among the hospital health workers. The proportion of people with antibodies also remains stable despite the resurgence of the virus in recent months.

We must interpret these results with caution. While they focus on an important component of our immune response against the SARS-CoV-2 virus, immunity cannot solely be attributed to the level of antibodies in the blood. Other factors, such as T-cells, also play an important role in the process.

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