Although few US military personnel have myopericarditis reactions to smallpox vaccinations, the number is high enough to be of concern if a larger population needs vaccination, the American Medical Association told a media briefing in New York last week.

Smallpox vaccination caused myopericarditis in 1.6 people per 10 000 who had never been vaccinated before, said Dr Dimitri Cassimatis, a cardiology fellow at Walter Reed Army Medical Center in Washington, DC. He reported results for more than 450 000 US military personnel. The rates of myopericarditis were higher than expected from reports from the 1950s to 1970s (Journal of the American College of Cardiology2004;43:1503-10).

Symptoms included burning sensations …