In response to claims that a man was denied a heart transplant because he refused to get vaccinated against COVID-19, Brigham and Women's Hospital in Boston said Wednesday that its transplant policies mirror those used across the United States.

In a crowdfunding appeal for 31-year-old D.J. Ferguson, a father of two, his family said the hospital told him he was ineligible to receive a new heart because he was not vaccinated, the Associated Press reported. His mother, Tracey Ferguson, said her son is not against vaccinations but has concerns about COVID-19 vaccines because he has atrial fibrillation. "D.J. is an informed patient," she told the AP. "He wants to be assured by his doctors that his condition would not be worse or fatal with this COVID vaccine."

Citing patient privacy laws, the hospital would not comment directly on the case. Instead, it noted that its website clearly states that the COVID-19 vaccine is one of several immunizations -- including a flu shot and hepatitis B vaccines -- required by most U.S. transplant programs, the AP reported. The hospital also said its policies line up with American Society of Transplantation recommendations, and that research shows transplant recipients already have a higher risk for death from COVID-19 than nontransplant patients.

Other U.S. hospitals have faced criticism for denying transplants to patients who were not vaccinated against COVID-19. A Colorado woman suffering late-stage kidney disease said in October that she was denied a kidney transplant because she was unvaccinated. Leilani Lutali, a born-again Christian, said she opposed immunization because of the role that fetal cell lines play in some vaccines' development.

But any surgery strains a patient's immune system and can leave them vulnerable to contracting COVID-19, and organ transplant recipients are even more vulnerable because they have to take powerful drugs that suppress their immune system to keep their body from rejecting the new organ, Nancy Foster, vice president for quality and patient safety policy at the American Hospital Association, said in a statement at the time of the Colorado case.

Because there is a shortage of donor organs, transplant centers only place patients on the waiting list whom they deem the most likely to survive with a new organ, experts said.