The study, which has not yet been published in a scientific journal and thus not reviewed, has analyzed antibody responses after two doses of Pfizer's vaccine in 539 people, of whom 449 have a weakened immune system.
Of those with a weakened immune system, 28 percent lacked antibody responses thirty-five days after their second vaccination.
In Sweden, it is estimated that about 40,000 individuals have a severely weakened immune system.
Several in this group are also extra susceptible to infections and thus also covid-19.
- The government, together with the Swedish Public Health Agency, recently announced that restrictions will be removed on 29 September and said that vaccinated people can in principle live as usual.
But according to our study, it is still uncertain whether those with severely weakened immune systems can live as usual, says Soo Aleman, chief physician and associate professor at Karolinska University Hospital.
Organ transplants stand out
In the study, the patients were divided into five different groups based on diagnosis.
Those who have been examined are HIV patients, patients with congenital immunodeficiency, patients who have had an organ transplant, patients who have had a stem cell transplant and patients with chronic lymphocytic leukemia.
However, antibody responses and levels varied widely between those with a weakened immune system.
Organ transplant transplant recipients had the lowest antibody response, with 57% lacking antibody response, and second worst patients with chronic lymphocytic leukemia, with 37% lacking antibody response after vaccination.
However, only 3 percent of HIV-infected patients lacked antibody responses.