Organ transplant recipients are less likely to develop antibodies than the general population, two recent Israeli studies have found.
The studies, which are in the process of being published by academic journals, were carried out by researchers at the Rabin Medical Center (Beilinson) and at Tel-Aviv’s Sourasky Medical Center.
The researchers focused on patients who had received a liver or a kidney transplant, and heart transplantees.
In both cases, the premise was that if infected, transplant recipients tend to develop more severe symptoms of COVID, and that the vaccine is far less effective for them.
“We knew that vaccine efficacy for the general population is about 95%, and we recommended our patients who underwent liver and kidney transplant to get vaccinated, based on preliminary studies showing that the outcome for this type of patients when infected with corona was worse than that of the general population,” Dr. Liane Rabinowich from Sourasky, who conducted the research together with Dr. Ayelet Grupper and Dr. Helena Katchman, told The Jerusalem Post.
“In addition, we knew that vaccinations tend to be less effective for transplant patients, based on other kinds of vaccines, like the one against pneumonia.”
“Two weeks after the second shot we checked vaccine efficacy,” she said.
Some 138 kidney transplant recipients and 80 liver transplant recipients participated in the study, as well as 25 individuals who did not present similar issues, to act as controls for the study.
“We saw that among the liver transplant patients only 47.5% developed antibodies, and only 37.5% of kidney recipients did,” Rabinowich said.
None of the patients showed to have antibodies before receiving the vaccine.
In addition, Rabinowich pointed out that those who did develop antibodies appeared to have a lower level than healthy individuals.
“However, we do not know the clinical significance of it,” she added.
Antibody development represents only part of the immune system’s defenses against a disease. The team is now checking the so-called cellular memory of patients to verify if the body built up other forms of protection.
The 42 heart transplant recipients who participated in the Beilinson study also appeared less likely to develop antibodies.
“We measured their antibodies after the first shot and after the second shot,” Dr. Osnat Itzhaki Ben Zadok from Beilinson said. “In the end, only about 50% of them developed them.”
“However, we did notice that some 36% of those who did not develop antibodies after the first shot did so after the second one,” she added.
“We are therefore looking into the possibility of giving our patients a third shot to see if this is going to help more of them to create antibodies. We are in contact with the Health Ministry for authorization.”
More real-world data are going to be crucial to better understand the actual protection offered by the coronavirus vaccine in all aspects.
Meanwhile, both experts recommended organ transplant recipients get vaccinated, noting that they did not register any severe side effects, and to continue to take other forms of safety measures, such as wearing masks.