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RESEARCH TORONTO GENERAL HOSPITAL RESEARCH INSTITUTE

Third

Time’s a

Charm

Clinical trial reveals that

COVID-19 booster is safe and

effective in transplant patients

The first randomized, placebo-controlled trial
of a COVID-19 booster vaccine in transplant
recipients has revealed that a third dose of the
Moderna vaccine is safe and induces a robust
immune response.

“We knew from previous studies that two doses
of vaccines are not enough to produce a strong
immune response against COVID-19 in transplant
patients,” says the joint-senior author of the study, vaccine group met these antibody levels.
Dr. Deepali Kumar. The research team also found that the booster
led to the production of T-cells and neutralizing
The clinical trial was randomized, double-blind antibodies, both of which specifically target
and placebo-controlled—providing a high level of and neutralize the virus. In the Moderna group,
rigour. A total of 120 transplant patients that had 60% tested positive for at least some ability to
not previously contracted COVID-19 and had neutralize the virus, compared to only 25% of
received two doses of the Moderna vaccine were participants on placebo.
enrolled in the trial.
In terms of safety, the booster vaccine was well
At the two-month mark after their second dose, tolerated, associated with only mild side effects
half of the participants received a third shot, and did not lead to organ rejection. “We found
while the other half received a placebo. The that the third dose was safe and increased immune
findings revealed that the booster shot increased responses in transplant patients. These findings
antibodies against the spike protein to levels that are quite definitive and tell us that third doses
are believed to provide at least 50% protection should be given to this vulnerable population to
against developing COVID-19. After three doses, help prevent COVID-19,” says Dr. Atul Humar,
only 18% of the participants in the placebo group Medical Director of the UHN Ajmera Transplant
showed this response, whereas 55% of those in the Centre, and the joint-senior author of the study.

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