Canadian researchers reported Wednesday that the third dose of Moderna’s COVID-19 vaccine tended to boost the immune response of organ transplant recipients whose immune systems are too weak to respond effectively to standard two shots.
The New England Journal of Medicine published the study, which was small but stated that a third-dose testing regimen is the most rigorous ever for this group.
Additional COVID Shots Protect Transplant Recipients
Even as Delta emerges as an increasingly contagious variant, Modern and similar vaccines provide thorough protection for the majority of people. Millions of people with suppressed immune systems, whether due to transplants, cancer, or other factors, rarely benefit from that kind of treatment. In France and Israel, extra doses have already been recommended and the U.S. is considering them. But there’s only limited evidence they help.
Two months after they received the second Moderna shot, researchers at Toronto’s University Health Network gave half of the transplant recipients a real third dose, and the other half received a fake dose. Immediately following the third dose, 55% of the third-dose recipients had high levels of antibodies to fight viruses, compared to the18% for those who had received two doses plus a placebo. Third-dose recipients also have a higher number of T cells, which help prevent severe illness. Antibodies are only one of the body’s defenses. There were no significant side effects.
Dr. Dorry Segev, a Johns Hopkins University transplant surgeon not involved with the study, says the findings offer “yet more evidence” that transplant recipients could benefit from an extra dose. Segev, who leads a U.S. study of extra shots for transplant recipients who are not protected, said it is important to check patients’ antibody levels before giving another shot as some of the transplant recipients had pretty good immune responses.
Enhancing antibody levels
During March and May, the researchers at Johns Hopkins University School of Medicine in Baltimore examined the antibody responses and the vaccine reactions in 30 organ transplant patients who had been administered a third dose of the coronavirus vaccine. Sixteen patients received Pfizer’s vaccine around 67 days after completing their second dose of the original vaccination, nine received Moderna’s vaccine and fifteen received Johnson & Johnson’s.
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Before receiving their third dose of vaccine, the researchers tested the patients for antibodies. There were no detectable antibody levels in 24 patients and low levels in six patients. About two weeks after receiving the third dose of vaccine, antibodies were tested again. All six patients with low antibody levels before receiving the third dose of their regimen had high antibody levels after receiving their third dose. The level of antibodies in the 16 patients with no detectable level remained undetectable after three doses. Six of them had high levels, two had low levels, and four were undetectable after two doses.
Approximately one week after receiving the third dose of vaccination, 23 patients who were evaluated reported typical reactions, such as soreness at the injection site, fatigue, headache, or disease. The researchers found mild signs of rejection in one heart transplanted patient a week after her third dose of an antirejection drug. She continued to function normally, and her immune system did not need to be intensified to treat the rejection. They noted that the woman didn’t have a rise in antibodies, and “it is uncertain” whether the mild rejection she experienced was a result of vaccination.
Segev and a colleague published a study in JAMA about a month ago concluding that, among 658 transplant recipients who received two doses of either Pfizer or Moderna vaccines, about half had no antibodies after two injections. The researchers found that 15% of participants produced measurable antibodies after the first and second doses and 39% did not produce antibodies after the first dose but developed antibodies after the second dose.