The FDA ( Food and Drug Administration ) has licensed a new vaccine to protect against smallpox, a highly contagious disease with the potential to be used as a deadly bioterror weapon.

The vaccine, ACAM2000, is intended for the inoculation of people at high risk of exposure to smallpox and could be used to protect individuals and populations during a bioterrorist attack. It will be included in the Strategic National Stockpile of medical supplies.

A worldwide vaccination program eradicated smallpox in the population. The last case of naturally occurring smallpox in the U.S. was in 1949 and the last case in the world was reported in Somalia in 1977. Known stockpiles of the virus are kept only in two approved labs in the United States and Russia. The CDC considers it a Category A agent, meaning it presents one of the greatest potential threats for harming public health.

Smallpox is caused by the variola virus, a virus that emerged in human populations thousands of years ago. It spreads through close contact with infected individuals or contaminated objects, such as bedding or clothing. There is no FDA-approved treatment for smallpox and the only prevention is vaccination.

The symptoms of smallpox typically began with high fever, head and body aches. A rash followed that spread and progressed to raised bumps and pus-filled blisters that crusted, scabbed, and fell off after about three weeks, leaving a pitted scar. The fatality rate historically was about 30 percent.

ACAM2000 is made using a pox virus called vaccinia, which is related to but different from the virus that causes smallpox. The vaccine contains live vaccinia virus and works by causing a mild infection that stimulates an immune response that effectively protects against smallpox without actually causing the disease.

The vaccine is derived from the only other smallpox vaccine licensed by FDA, Dryvax, approved in 1931 and now in limited supply because it is no longer manufactured.

Although smallpox vaccination ended in the United States in 1972 because it was no longer needed for prevention, the U.S. military resumed vaccination of at-risk personnel in 1999, after concluding that the disease posed a potential bioterrorism threat.

Source: FDA, 2007

XagenaMedicine2007



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