TORONTO, Ontario — A COVID booster shot has been a topic of debate ever since the coronavirus vaccine was developed last year. Will a third shot be necessary to fully protect the general public? Scientists are still unsure. However, a world-first study reveals that COVID vaccine boosters will definitely benefit certain individuals during the pandemic — specifically, transplant patients.
Scientists with the Ajmera Transplant Centre in Toronto have discovered that a third dose of the COVID-19 vaccine provides greater immune protection for those who have had organ transplant surgery. The findings of the randomized placebo-controlled trial show that transplant patients show a significant uptick in both antibody and T-cell response to the virus.
“We knew from previous studies that two doses were not enough to produce a good immune response against COVID-19 in transplant patients,” says Dr. Deepali Kumar, Director of Transplant Infectious Diseases at University Health Network, in a media release.
“Based on our study, a third dose of COVID vaccine is definitely the best way to increase protection in transplant recipients.”
The third shot’s the charm
Researchers studied the effectiveness of a third vaccine dose on 120 transplant patients between May 25 and June 3. No one in the group had contracted COVID-19 before the study and all had previously received two doses of the Moderna COVID vaccine. During the experiment, half of the patients received a COVID booster shot while the other half received a placebo.
The team was looking for antibody levels greater than 100 U/ml against the spike protein of SARS-CoV-2. Results show an almost 40-percent increase in antibody levels in participants receiving a third vaccine injection. In patients receiving the placebo, the antibody response rate was only 18 percent. However, the group receiving the booster shot had an antibody response of 55 percent.
“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. “The third dose was safe and well tolerated and should lead to a change in practice of giving third doses to this vulnerable population.”
Additionally, study authors find that the effectiveness of neutralizing antibodies also increased after a third COVID dose. Neutralizing antibodies attack and shut down viruses. In this case, 60 percent of the participants in the Moderna group developed neutralizing antibodies against COVID. Only 25 percent of the placebo group had them in their systems.
The team also discovered a big difference in T-cell response in the booster shot group. T-cells help the immune system prevent severe disease in patients. Researchers note that transplant patients in the three-shot Moderna group experienced a “robust T-cell response” against COVID.
No major side-effects
Study authors report that the third booster vaccine did not cause any major side-effects for transplant patients. Participants only had mild reactions to the injection. Moreover, the third vaccine did not trigger any cases of acute organ rejection, which is a serious concern for transplant recipients getting multiple vaccinations.
The Canadian team has already shared their findings with the U.S. Food and Drug Administration, the American Society of Transplantation, and other health agencies worldwide.
“Our goal is to help coordinate the efforts of provincial and national organizations that are involved in public health and vaccination research and facilitate information sharing among public health agencies and patient partners,” Dr. Kumar concludes.
The findings appear in the New England Journal of Medicine.