Ontario recommends Pfizer over Moderna for young adults

The province has issued a preferential recommendation of the use of Pfizer for young people between 18 and 24.

Elizabeth Payne 3 minute read September 30, 2021

Ontario is recommending young adults receive the Pfizer COVID-19 vaccine instead of Moderna because of an increased risk of a rare heart condition — especially among young men.

The province announced Wednesday that “out of an abundance of caution” it has issued a preferential recommendation of the use of Pfizer for young people between 18 and 24. That means Pfizer is the preferred vaccine, but those who choose to can still received Moderna. Teens between 12 and 17 already receive just Pfizer doses.

The decision is based on information from Ontario’s adverse events following immunization surveillance system about myocarditis, which is inflammation of the heart and pericarditis, inflammation of the lining of the heart.

Ontario was responding to recent data from the province which found that between June 1 and Aug. 7, 2021, based on more than 96,000 doses, the risk of myocarditis and pericarditis for males between 18 and 24 following a second dose of Moderna was one in 5,000. The rate after Pfizer was 1 in 28,000.

The reaction is most common after second doses and more common in young males, officials said. But the majority of cases observed in Ontario were mild and short-lived, usually treated with anti-inflammatory drugs and rest. A small number ended up in ICU, but usually for monitoring. There were no related deaths.

The risk of myocarditis/pericarditis and other serious health issues from COVID-19 infection is higher.

The issue has been observed in other countries and has become the focus of some anti-vax groups especially since a pre-print study from the University of Ottawa Heart Institute incorrectly calculated the risk of myocarditis as significantly higher than it is. The study has since been withdrawn, but not until it spread like wildfire through the anti-vaccine community.

On Wednesday, Ontario’s Chief Medical Officer of Health, Dr. Kieran Moore, said he is aware that myocarditis has been a source of vaccine hesitancy among some and had concerns about addressing it.

“But I have to build trust with the public and the public deserves to know the facts on the risk,” he said. “We have a robust adverse events surveillance system informed by eminent groups. All of those groups recommended that we inform the public of this increased risk of a very rare event.”

Moore also said that two of his sons are between 20 and 23 and both received Moderna vaccines.

“It is an excellent product that has a very good immune uptake and I have complete confidence in it, but we must be accountable and transparent. I hope the public sees that this is our means of building trust in the vaccine delivery system.”

Earlier, Ontario and other provinces stopped offering AstraZeneca vaccines after studies showed an increased risk of rare blood clots.

Provincial officials say symptoms related to myocarditis and pericarditis usually start within one week after vaccination, more commonly after a second dose.

“Individuals who have not developed symptoms within this timeline should feel confident that they are unlikely to develop symptoms later,” a provincial briefing document read.

The province also said those who received a first dose of the Moderna vaccine “absolutely did the right thing to protect themselves, their loved ones and communities.”

Earlier, some of those administering vaccinations reported a preference for Pfizer over Moderna, something provincial and public health officials attempted to overcome. Recent studies have given Moderna a slight edge over Pfizer when it comes to protection against the Delta variant. Both mRNA based vaccines offer high protection against serious illness and death.