Third injection of Moderna boosts immune response in transplant recipients, Canadian trial finds

A randomized clinical trial in Canada has found that three doses of the Moderna vaccine are effective in stimulating the immune response of organ transplant recipients to the coronavirus, suggesting they may be better protected against disease and infection. The discovery could lead to the accelerated approval of third jabs for this vulnerable population.

Solid organ transplant recipients taking immunosuppressive drugs are often excluded from clinical vaccine trials, but like CDC’s Anthony Fauci Recount CNN’s State of the Union last month, a third jab would likely go a long way in protecting immunosuppressed people from covid-19.

The challenge is to ensure that vaccines are both safe and effective for transplant patients with weakened immune systems. To this end, the Canadian government, through its COVID-19 Immunity Working Group and its Vaccine Surveillance Reference Group, spear PREVENT COVID (Prospective evaluation of the COVID-19 vaccine in transplant recipients: a national strategy). The US $ 2.27 million research program is being conducted at the University Health Network, a research hospital affiliated with the University of Toronto.

This group is closely monitoring transplant patients to see how they respond to covid-19 vaccines, which so far has not been great. Hence the hope of a third jab.

The team knew of previous studies that “two doses were not enough to produce a good immune response against COVID-19 in transplant patients,” said Deepali Kumar, a transplant physician at the UHN Transplant Center and co-lead author of the new study, in a statement.

A third dose seemed like the logical answer, but there were concerns that repeated vaccinations could increase the chances of organ rejection. Accordingly, the aim of the recently completed project was to assess the response of transplant recipients – who take immunosuppressive drugs to prevent organ rejection – to a third dose of vaccine.

For this randomized, double-blind study, the team studied 120 transplant patients from May 25 to June 3 of this year. The median age of the patients was 66.6 years, none had previously contracted covid-19, and all had previously received two doses of Moderna vaccine (mRNA-1273 vaccine). The results of this research are published today in the New England Journal of Medicine.

The group was split into two: half received a third injection of Moderna two months after receiving the second injection and the other half received a saline placebo. Patients in the three-dose Moderna group experienced mild side effects and, most importantly, no serious health effects.

“We followed the patients very closely to look for evidence of acute organ rejection and for any changes in the function of their transplanted organ,” said Atul Humar, medical director of UHN’s Ajmera Transplant Center and co. – principal author of the study, in a press release. E-mail. “We had no patient who developed rejection during the study follow-up period. “

The antibody response rate for patients in the three-dose Moderna group was measured at 55%, while it was closer to 18% in the placebo group. Neutralizing antibodies were detected in 60% of patients receiving three doses and in 25% of patients receiving placebo. Scientists have also documented an increased production of T cells – a powerful ally in the body’s fight against infection – among the three-dose Moderna group.

“We conclude that a third dose Covid-19 booster vaccine should be considered, in conjunction with regulatory approval, for transplant recipients who have received two doses of mRNA-1273. [Moderna]”, Wrote the scientists in their study.

Scientists chose Moderna because it contains a higher dose of antigen than Pfizer (antigens are molecules that stimulate an immune response). That said, “we believe the results are applicable to the Pfizer vaccine because it has a very similar mechanism of action,” meaning both are mRNA vaccines, Humar explained. As for the patients who received AstraZeneca, “further trials would be needed to confirm the optimal booster regimen,” he added.

I also asked Humar about this dreaded variable, the Delta variant, and whether this was taken into account in the new study.

“Because we measured several aspects of the immune response, we believe the results will apply to protection against the Delta variant,” he replied. “We are currently conducting follow-up studies to help confirm this. “

The team is now hoping for “a change in regulatory guidance to recommend [a] third-dose vaccine for transplant patients who have received two doses of mRNA vaccine, ”Humar wrote. To that end, they shared their findings with the U.S. Food and Drug Administration (FDA), Canadian National Advisory Committee on Immunization (NACI), American Society of Transplantation, among other institutions.

This is great news, especially given the recent peak in covid cases around the world and the worrying rise of the Delta variant. It is also great to see that steps can be taken to protect immunocompromised patients, a population that already has enough cause for concern.