Australia versus the U.S. You just got to love the choice of words and the disparity in statistics. This is not unique to Australia though. The US is the outlier versus other countries.
Australia - Myocarditis, or inflammation of the heart muscle, and pericarditis, or inflammation of the lining around the heart, are serious but rare side effects associated with mRNA vaccines.
According to the TGA, myocarditis which it describes as "very rare" is reported in about one to two out of every 100,000 people who receive Pfizer and two to three out of 100,000 who receive Moderna.
But it is more common after the second dose in teenage boys at 12 cases per 100,000 for Pfizer and 17 per 100,000 for Moderna, and young men under 30 at six per 100,000 for Pfizer and 12 per 100,000 for Moderna.
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USA - Reports of more serious effects following vaccination in children in the US were extremely rare with 100 reports from 8.7 million vaccine doses the most common were fever, vomiting and in some cases seizures," it said.
Importantly, myocarditis was also very rare in this age group (12-17), with 11 confirmed reports from over eight million doses these were all mild cases.
https://www.news.com.au/lifestyle/health/health-problems/tga-confirms-first-cases-of-myocarditis-linked-to-booster-shots/news-story/a0211e1242c66366e21d83a54aa7a298