The U.S. 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
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 Center for Disease Control and
Prevention's (CDC) 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 licensure of ACAM2000 supplements our current supply of
smallpox vaccine, meaning we are more prepared to protect the
population should the virus ever be used as a weapon," said Jesse L.
Goodman, M.D., M.P.H., director of FDA's Center for Biologics
Evaluation and Research. "This vaccine is manufactured using modern
cell culture technology allowing rapid and large scale production of
a vaccine with consistent product quality."
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, according to the CDC.
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.