A third dose of a two-shot COVID vaccine significantly boosts transplant patients' protection against SARS-CoV-2, according to a new study.
"We knew from previous studies that two doses were not enough to produce a good immune response against COVID-19 in transplant patients," said study co-senior author Dr. Deepali Kumar. She is director of transplant infectious diseases at the University Health Network (UHN) in Toronto and professor of medicine at the University of Toronto.
"Based on our study, a third dose of COVID vaccine is definitely the best way to increase protection in transplant recipients," Kumar said in a UHN news release.
The study of 120 transplant patients was conducted between May 25 and June 3. None of the patients had COVID previously and all had received two doses of the Moderna mRNA vaccine.
Half of the patients received a third shot (booster) two months after their second dose, and the other half received a placebo.
In all, 55% of patients who got the booster and 18% of those in the placebo group achieved an antibody level above 100 U/ml against the virus' spike protein, the researchers' primary outcome.
But there was more: 60% of booster recipients developed antibodies that neutralize the virus compared with 25% of the placebo group.
Those in the booster group were also more likely to develop a robust T-cell response against the SARS-CoV-2 virus. T-cells are another part of the immune system that work to prevent severe disease.
The findings were published Aug. 11 in the New England Journal of Medicine.
"This is an important win for our patients because the results are quite conclusive," said study co-senior author Dr. Atul Humar, medical director of the Ajmera Transplant Centre at UHN. "The third dose was safe and well tolerated and should lead to a change in practice of giving third doses to this vulnerable population."
Researchers said this was first randomized placebo-controlled trial of a third dose COVID-19 booster vaccine for transplant patients.
The findings have been shared with agencies such as the U.S. Food and Drug Administration, the Canadian National Advisory Committee on Immunization, the American Society of Transplantation, and others in the hopes of getting expedited approval of booster shots for transplant patients.
The American Society of Transplantation has more on COVID-19.
SOURCE: University Health Network, news release, Aug. 11, 2021