Research shows 3rd dose of COVID-19 vaccine could help better protect organ transplant patients

New research suggests a third dose of a COVID-19 vaccine could help better protect organ transplant patients.

Researchers at the University Health Network (UHN) in Toronto say their study released today “shows a clear benefit” to offering a booster to this immunocompromised group.

The study’s joint senior author Dr. Deepali Kumar says some transplant patients “are completely unprotected” with two doses and should be offered a third.

“We knew from previous studies, that two doses were not enough to produce a good immune response against COVID-19 in transplant patients,” says Kumar, Director of Transplant Infectious Diseases, UHN and joint-Senior Author of the study published today in the New England Journal of Medicine.

“Based on our study, a third dose of COVID vaccine is definitely the best way to increase protection in transplant recipients.”

The study enrolled 120 transplant patients between May 25 and June 3. Researchers compared 60 participants in Ontario who received a third shot of the Moderna vaccine to 60 who got a placebo.

Just over half, or 55 per cent, of those who received the third dose, saw their antibody response rate reach at least 100 units per millilitre, which the previous modelling suggests offers some protection.
In comparison, 18 per cent of the placebo group reached 100 units.

Kumar says antibody levels typically reach 1,000 to 10,000 units per millilitre in healthy people, and some of the transplant study participants showed similar numbers.

The study is billed as the first randomized placebo-controlled trial of COVID-19 boosters in transplant patients.

“This is an important win for our patients because the results are quite conclusive,” says Dr. Atul Humar, Medical Director of the Ajmera Transplant Centre, UHN and the joint-Senior Author of the clinical trial.

“The third dose was safe and well-tolerated and should lead to a change in practice of giving third doses to this vulnerable population.”

The study also concluded that 60 per cent of the patients in the Moderna group “developed neutralizing antibodies versus 25 per cent in the placebo group.”

“We were able to do this because our team worked non-stop for months,” said Dr. Humar. “And we are in a global emergency, lucky enough to have generous philanthropic donors and an existing vaccine trials infrastructure already set up.”

Health officials say fully vaccinated people have greater protection against COVID-19 than unvaccinated people, including against the Delta variant.

In Toronto, nearly 73 per cent of people age 12 and older are now fully vaccinated.