Research by UZ Brussel among employees shows that they only have antibodies against the virus for a few months after they have become infected. A Dutch study is talking about six months.
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The UZ Brussel survey involved 2,662 of the approximately 3,800 hospital employees. Of these, 7.4 percent tested positive for antibodies in phase 1 (May 18 to June 12), 6.8 percent in phase 2 (July 13 to August 7) and 5.5 percent in phase 3 (October 5 to 30). That percentage is hardly higher than that of the general population. The research focuses specifically on the antibodies and whether they remain in the body of the positive cases. Now it turns out that they could be gone in a few months. Of the 185 participants with antibodies in phase 1, only half appeared to still have antibodies in phase 3.
“The exact reason is not yet clear, but the study does show the importance of continuing to follow up all protective measures, even after an infection,” says Professor Sabine Allard, head of internal medicine clinic.
Those who test positive and are infected do not necessarily produce antibodies afterwards. 10.2 percent of the participants who were positive in phase 1 were found to have no antibodies. In stages 2 and 3, 24.2 percent of positive hospital employees had no antibodies.
Especially young adults
Researchers from the Netherlands National Institute for Public Health and the Environment (RIVM) came to a slightly more positive conclusion. A large ongoing study into immunity to the virus found that 90 percent of people who were infected still had antibodies in their blood six months later. In addition, they became stronger over time, reducing the need to do the same work.
Every few months, the RIVM uses a sample of thousands of people to examine how many of them have antibodies in their blood. In the last round, in September and October, some 6,500 blood samples were examined. 4.9 percent of the participants had antibodies against sars-CoV-2 in their blood. Much of that was taken off before the peak of the second wave. Of all age groups, young adults (20-30 years old) most often have antibodies in their blood: about 10 percent.
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