Smallpox jab intended for US biodefence may inflame heart

http://bepast.org/disease_information/Smallpox/Smallpox%20Disease%20Information/smallpox%20vaccine%20trial%20halted.mht

心包炎  myopericarditis

Three of the participants developed myopericarditis. Two of these people had slight chest pains, while the third had no symptoms, but showed signs of internal inflammation.

============================================================
Health fears halt vaccine trial
Smallpox jab intended for US biodefence may inflame heart
15 April 2004
ALISON ABBOTT
Both old and new smallpox vaccines may cause heart trouble.
© GettyImages 

Recruitment for clinical trials of a smallpox vaccine being mass-produced for the US government has stopped after three cases of a heart condition cropped up in participants.

The US Centers for Disease Control and Prevention and the US Food and Drug Administration are now discussing how to proceed with the trials.

The vaccine, called ACAM2000, is being developed by the biotechnology company Acambis, based in Cambridge, UK. Acambis won a contract from the US government, which wanted to stockpile smallpox vaccine in response to perceived threats of bioterrorism. Officials were willing to begin mass production of the vaccine before clinical trials had been completed.

Officials had a hint that cardiac problems might crop up, thanks to recent vaccinations with an older, similar vaccine called Dryvax, which was once used to wipe out natural cases of smallpox.

Dryvax's manufacture ceased in the early 1980s, a few years after smallpox was eradicated. But in the United States some 600,000 soldiers and 40,000 civilians deemed to be at high risk of exposure to bioterror attacks were recently vaccinated with old stores of this jab. Of these, 95 people developed a heart problem called myopericarditis, which is an inflammation of the heart and surrounding tissues.

The two vaccines are quite similar: both include the virus that causes cowpox, called vaccinia. So Acambis trial participants were being carefully monitored for similar cardiac side-effects.

Chest pains

Acambis launched two trials of the vaccine, starting in December 2003 and January 2004. Together, some 2,800 people have received either the ACAM2000 or the Dryvax vaccine.

Three of the participants developed myopericarditis. Two of these people had slight chest pains, while the third had no symptoms, but showed signs of internal inflammation.

Both vaccines appear to be causing the problem. Two of the cases were caused by one vaccine, and one case was caused by the other.

The main difference between the vaccines is their method of manufacture. Dryvax was made by growing vaccinia on cow bellies, making it a relatively expensive and difficult endeavour. The ACAM2000 vaccine is made using more modern cell culture techniques, which should provide a purer product.

© Nature News Service / Macmillan Magazines Ltd 2004