Concerned by cardiac problems among some recipients of the smallpox vaccine, an advisory panel last week recommended that the Centers for Disease Control and Prevention (CDC) in Atlanta postpone the planned expansion of its vaccine effort. The recommendation of the Advisory Committee on Immunization Practices (ACIP) dealt another blow to the civilian program, announced by President George W. Bush on 13 December and already stalled because of a dearth of volunteers (Science, 9 May, p. 880). CDC says it will weigh the recommendation but for now intends to forge ahead.
Previous experience with the so-called Dryvax vaccine, used routinely in the 1960s and early 1970s, had officials worried about several serious vaccine-related effects, including encephalitis. These have been rare. But heart trouble has been more common among the 37,000 civilians and 450,000 military workers immunized with the stockpiled vaccine this time around. At least 21 and 37, respectively, have developed nonfatal inflammation of the heart, called myopericarditis; three other vaccine recipients suffered fatal heart attacks, which have not been definitively tied to vaccines.
In one of the first analyses to date of the heart problems, a paper in the 25 June Journal of the American Medical Association reports on 18 cases of myopericarditis in the military, including biopsy findings from one. Heart tissue from that individual revealed infiltration of white blood cells called eosinophils. These are "not the typical virus-fighting cells," says co-author Gregory Poland, head of the Mayo Clinic's vaccine research group in Rochester, Minnesota. He wonders whether it's not vaccinia, the virus used to induce smallpox resistance, but some other component of the vaccine that's prompting inflammation, perhaps bovine cells from the manufacturing process.
ACIP doesn't discourage states from finishing the early phase of vaccination--inoculating the "first responders"--but urges against scaling up to include others, such as police and firefighters. CDC hasn't determined how it will proceed. "We're still moving forward," says CDC spokesperson Von Roebuck. The question of whether to broaden the program, though, may be moot. The number of volunteers has slowed to roughly 100 people a week, say CDC officials, making it unlikely that the agency will reach its original goal of up to 10 million vaccinees anytime soon.