Myocarditis data from Ontario Province: Specific Vaccine & Interval between Doses | A Must Read!
What this video covers
In this December 2021 video, Prasad discusses a Canadian preprint analyzing myocarditis cases in Ontario, linking to the medRxiv paper and to an op-ed he co-authored for MedPage Today. The video focuses on two findings he considers pivotal: that myocarditis risk differed by vaccine product — highest after a second dose of Moderna — and that longer intervals between the first and second doses were associated with lower risk.
Prasad presents the Ontario data as evidence that vaccine-safety policy should have been more granular. According to his argument, regulators treated all mRNA products and all dosing schedules as interchangeable when the data showed meaningful differences — differences, he contends, that could have been used to reduce harm, for example by preferring Pfizer over Moderna for young men or by spacing doses further apart. He frames the failure to act on such distinctions as another instance of one-size-fits-all policymaking.
The numbers he highlights are stark. In men aged 18–24, two Pfizer doses produced a myocarditis rate of roughly 46 per million at the second dose; two Moderna doses given less than 30 days apart produced 376 per million — about 1 in 3,000 to 4,000, consistent with the highest global estimates from Israel and Norway. Pfizer followed by Moderna was the worst combination at 777 per million, roughly 1 in 1,200 — among the highest rates he had seen anywhere — while Moderna followed by Pfizer had the lowest rates. And intervals longer than 55 days were associated with lower risk. He also applies the findings to the Los Angeles school mandate then under debate — roughly 34,000 noncompliant students facing expulsion — citing his own U.S. News op-ed urging a pause, on the grounds that the mandate’s rigid schedule blocked the known mitigation strategy of dose-spacing.
The chronicle notes that other countries did act on similar data: several European nations restricted Moderna use in younger age groups and extended dose intervals in 2021, citing myocarditis findings. U.S. regulators maintained both products’ availability with updated warnings. Prasad’s supporters cite the Ontario study as vindication of product- and schedule-specific policy; critics respond that the U.S. approach — surveillance plus labeling updates — reflected the same data weighed differently against the risks of delayed vaccination during an active pandemic.
Key points
- Prasad reviews an Ontario preprint finding myocarditis risk varied by vaccine product, with the highest rates after a second Moderna dose.
- The specific figures he highlights, in men 18–24: two Pfizer doses, ~46 per million; two Moderna doses under 30 days apart, 376 per million (~1 in 3,000–4,000); Pfizer followed by Moderna, 777 per million (~1 in 1,200); Moderna followed by Pfizer, the lowest rates.
- He highlights the finding that longer intervals between doses — over 55 days — were associated with lower myocarditis risk.
- He applies the findings to the Los Angeles school mandate then under debate, citing his U.S. News op-ed urging a pause for roughly 34,000 noncompliant students facing expulsion.
- According to Prasad, regulators should have differentiated policy by product and schedule rather than treating all mRNA vaccines identically.
- He argues options like preferring Pfizer for young men or spacing doses could have reduced harm.
- The chronicle notes several European countries did restrict Moderna in younger groups or extend intervals, citing similar data.
- Critics of Prasad’s framing respond that U.S. regulators weighed the same findings against the risks of delaying vaccination during a pandemic surge.