AMSTERDAM - Multiple hospitals in the Netherlands noticed that people with weak immune systems were hospitalized with Covid-19 even after being fully vaccinated against the disease. The hospitals are therefore investigating whether vulnerable patients could benefit from a third dose of Covid-19 vaccine, AD reports.

"But those are not people who are otherwise perfectly healthy," Bram Goorhuis, internist and coordinator of the coronavirus department at Amsterdam UMC, said to the newspaper. All cases of vaccinated people becoming so sick from Covid-19 that they needed hospitalization at the Amsterdam hospital involved people with a weak immune system, for example due to treatments that shut down the immune system such as for cancer or organ transplants. 

Of the Covid-19 vaccines currently being used in the Netherlands, all but the one developed by Janssen require two doses to offer sufficient protection to prevent serious illness from Covid-19 in most people. The Janssen vaccine only requires one shot. Dutch hospitals are now investigating exactly which people do not build up sufficient protection against the disease after two injections, and whether they could benefit from a third shot. 

The hospitals are conducting research in various groups. Part of this research involves measuring the immune response of around 800 people undergoing chemotherapy or immunotherapy 28 days after their second vaccination. Maastricht UMC is investigating each case of a patient being hospitalized with Covid-19 after both shots, to make sure this did not have to do with a specific coronavirus strain. So far, that does not seem to be the case. "We were able to establish that it happened due to an insufficient immune response in patients with other disorders," internist at the hospital Coen Stehouwer said. 

The hospitals  stressed that the vaccinations are working well for most people. The number of Covid-19 related hospitalizations is falling sharply, with only occasional patients coming in after their first injection. "This picture fits within the 'margin of error' of vaccination studies, where there is no 100 percent coverage, but there is a much smaller chance of admission," Annemarie Buntsma of the Fevloziekenhuis said to AD.