Ontario recommends Pfizer over Moderna for young adults due to myocarditis risk

A pharmacist draws a dose of the Pfizer-BioNTech COVID-19 vaccine in Toronto, Friday, June 18, 2021. THE CANADIAN PRESS/Nathan Denette

TORONTO - An increase in cases of a rare heart condition among young adults who received the COVID-19 Moderna vaccines has prompted Ontario to recommend the Pfizer-BioNTech shots for those aged 18 to 24.

Ministry of Health officials made the recommendation on Wednesday, noting that cases of myocarditis and pericarditis had been particularly observed among males in that age group.

The province's top doctor said the benefits of vaccination against COVID-19 far outweigh the risks, but noted he made the recommendation out of an "abundance of caution" and to be transparent with the public.

"I have to build trust with the public, we have to have accountability to the public, and I think the public deserves to know the facts on the risks that we've identified in Ontario," Dr. Kieran Moore told reporters on Wednesday.

He stressed that risk remains "very rare" and symptoms resolve quickly, and noted that his own children who are in the age group affected by the recommendation received Moderna shots with no issues.

Moore also pointed out that myocarditis, along with other conditions like blood clots, arrhythmia and pulmonary embolism are also documented side effects from COVID-19 infections.

"Vaccines are safe, they are effective at protecting us and have significantly reduced the risk of infection, hospitalization, and the use of the intensive care units in Ontario alone," he said. "They continue to be the best way to protect our young adults, their families, and our communities from COVID 19."

Between June and August, the province said the risk of myocarditis and pericarditis for males aged 18 to 24 following a second dose of Moderna was one in 5,000.

For those who received the Pfizer-BioNTech shot, the rate was one in 28,000.

That data was based on 96,000 second doses of vaccines administered to males in that age group.

Most cases occur within the first week after receiving a second dose of vaccine and are treated with anti-inflammatory medication.

Officials said no deaths have been associated with the condition and fewer than 10 people have been admitted to intensive care with it.

Almost all cases have been diagnosed in emergency rooms and many are hospitalized, officials said, but hospital stays are typically short.

Myocarditis is an inflammation of the heart muscle and pericarditis is an inflammation of the sac around the heart. Symptoms include chest pain, shortness of breath, irregular heartbeat, fatigue or general malaise.

The province's recommendation takes effect immediately but people can still take Moderna vaccines if they choose to, with informed consent. People who received Moderna as a first dose can take Pfizer-BioNTech as a second dose, officials said.

Provincial data showed that as of Wednesday, 86 per cent of people aged 12 and older had at least one dose of a COVID-19 vaccine and 80 per cent had received both shots. Moore has said the province is aiming for close to 90 per cent vaccination coverage.

Immunization rates are slightly lower for people aged 18 to 29, of whom eighty per cent have received one vaccine dose and 71 per cent have both shots. People aged 30 to 39 also have lower rates of vaccination than the overall total.

The lower vaccination rates among young adults is a source of concern for public health officials in Toronto.

Dr. Eileen de Villa, the city's medical officer of health, said approximately 189,000 Toronto residents between 30 and 49 aren't yet vaccinated. She pointed to the group -- many of whom may be parents of young children who can't yet get the shots -- as painting a "telling picture" about the risks of remaining unvaccinated.

"It's reasonable to assume that they will become infected with COVID-19 and likely with the Delta variant," she said. "If too many of the unvaccinated get sick at the same time it could be catastrophic for the health system."

She also pointed to modelling released by the province's science advisers on Tuesday, which found COVID-19 infections and hospitalizations have stabilized but the pattern could shift quickly.

"We are again on the verge of a risky and uncertain period in the pandemic," De Villa said.

Toronto also announced on Wednesday that it would host pop-up clinics in all 25 city wards on Saturday in a push to boost coverage and offer shots in convenient locations for residents.

"If you need your first dose, or your second dose, there are 35 clinics across Toronto at the ready, trying to help you to do the right thing," Mayor John Tory said.

Ontario reported 495 COVID-19 cases and eight deaths from the virus on Wednesday. There were 172 people hospitalized with COVID-related critical illness and 123 people on ventilators.

This report by The Canadian Press was first published Sept. 29, 2021.

The Canadian Press. All rights reserved.