Minneapolis (dpa) - The agent hydroxychloroquine does not protect contact persons of Sars-CoV-2-infected against infection. This is the result of a study by American scientists.

They had prescribed the drug to people who, without mouth or eye protection, had been within a distance of less than 1.80 meters for at least 10 minutes from a person who was proven to be infected. Those affected later fell ill with Covid-19 with the same probability as contact persons who had received an ineffective sham drug. The researchers present their results in The New England Journal of Medicine.

The team led by David Boulware from the University of Minnesota sought participants for their study on social media channels and on traditional media platforms. The volunteers received the product, which was originally developed for the treatment of malaria and certain immune diseases, by mail and asked to take it according to the instructions. It had to be taken no later than four days after the unprotected contact. In the weeks after, the researchers questioned the participants several times about their state of health.

107 of the 821 contact persons developed Covid-19 within 14 days. The infection was not confirmed in all patients with a test, in most cases the researchers concluded that the disease was due to the symptoms. The proportion of sufferers was roughly the same in both groups - the hydroxychloroquine and placebo groups. The drug is therefore not suitable for preventing illness, the researchers write. They restrict that their participants were primarily young and did not belong to any risk group. Whether the product is used for prevention in high-risk patients must be examined further.

The effectiveness of hydroxychloroquine in existing diseases is currently being tested in studies. Previous research has shown no evidence that it improves symptoms or shortens the duration of the illness. The drug is also under special scrutiny because US President Donald Trump has repeatedly praised it as a miracle cure and stated that it was taken prophylactically to protect itself against the virus.