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Consumer Update |
FDA has licensed a new vaccine to protect against smallpox, a highly contagious viral disease that has the potential to be used as a deadly bioterrorism weapon.
The vaccine, ACAM2000, is intended to inoculate people at high risk of being exposed 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 to be used to respond to national emergencies.
ACAM2000 is made using a pox virus called vaccinia, which is related to the virus that causes smallpox. The vaccine contains live vaccinia virus and works by causing a mild infection that stimulates an immune response, which effectively protects against smallpox without actually causing the disease.
The vaccine is derived from the only other smallpox vaccine, Dryvax, licensed by FDA, which was approved in 1931 and is now in limited supply because it is no longer manufactured. ACAM2000 is manufactured by Acambis Inc. of Cambridge, England, and Cambridge, Mass. Dryvax was made by Wyeth Laboratories Inc. based in Madison, N.J.
ACAM2000 was studied in two groups of people:
The percentage of unvaccinated people who developed a successful immunization reaction was similar to that of Dryvax. ACAM2000 also was found to be acceptable as a booster in those previously vaccinated for smallpox.
A worldwide vaccination program eradicated smallpox. The last naturally occurring case in the United States was in 1949 and the last case in the world was reported in Somalia in 1977. Only two approved labs in the United States and Russia keep known stockpiles of the virus.
Smallpox is caused by the variola virus, which emerged in people 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.
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.
The symptoms typically began with high fever and 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. About 30% of people infected with smallpox died, according to the Centers for Disease Control and Prevention.
Because ACAM2000 contains live vaccinia virus, people who receive the vaccine must be careful to prevent the virus from spreading from the inoculation site to other parts of the body and to other people.
To minimize known risks, a Risk Minimization Action Plan (RiskMAP) is required as part of the vaccine licensing. The RiskMAP requires providers of the vaccine and patients to be educated about the vaccine's risks. To help educate patients, a Medication Guide is required to be given to them. The guide explains the proper care of the vaccination site and discusses serious side effects that can occur with ACAM2000.
In studies, about 1 in 175 healthy adults who received smallpox vaccine for the first time developed inflammation and swelling of the heart or surrounding tissues (myocarditis and pericarditis). Of the 10 affected adults, four had no symptoms and at the end of the study, all but one had their symptoms go away.
Date Posted: Sept. 4, 2007
