An Update on Smallpox
By Michelle Meadows (staff writer for FDA Consumer)
The last confirmed case of smallpox in the United States occurred in 1949, and the last naturally occurring case in the world was recorded in Somalia in 1977. Three years later, the World Health Organization declared that smallpox had been eradicated. But if terrorists were to intentionally introduce just a single case of smallpox today, it could mushroom into a public health emergency, experts say.
In December 2002, President Bush announced a comprehensive plan to protect Americans from smallpox if it were to be used in a bioterrorist attack. The plan addresses actions to quickly contain an outbreak through vaccination. As part of this plan, the U.S. Department of Health and Human Services (HHS) has been working with state and local governments to develop a national stockpile of smallpox vaccine.
The only smallpox vaccine currently licensed by the Food and Drug Administration is Dryvax (smallpox vaccine, dried, calf lymph type), made by Wyeth Laboratories Inc. in Marietta, Pa. "The vaccine was first approved in 1931, and the existing lots were manufactured in the 1970s and early 1980s and stored frozen," says William Egan, deputy director of the FDA's Office of Vaccine Research and Review. "The vaccine lots remained fully potent."
In October 2002, the FDA approved a license supplement for a 100-dose kit of Dryvax, with a new supply of diluent (the liquid that's mixed with dried vaccine before it's administered) and needles for administration, Egan says. "Before the approval of this supplement, Dryvax was available only under an investigational new drug (IND) application. Now the vaccine can be distributed and used as any other approved product." Along with Dryvax, there are several other smallpox vaccines that are being evaluated under INDs.
The potential threat of smallpox as a biological weapon has raised plenty of questions about the disease and the vaccine. Here are some answers from the FDA and the Centers for Disease Control and Prevention (CDC).
Q. Does smallpox pose a significant threat as a weapon?
A. There is no proof of any threat right now, but the CDC recognizes it as a possibility. In light of the terrorist attacks in September and October 2001, including the use of anthrax, the smallpox plan was developed as a precautionary measure. Smallpox is particularly dangerous because it can be spread from person to person, has a high rate of mortality, and there is no known cure (although it can be prevented through vaccination).
Q. How is smallpox spread?
A. Smallpox is caused by the variola virus, which is spread through close contact with a person who has symptoms of the disease. A person with smallpox has infected saliva, and face-to-face contact can spread the virus. The virus could also be spread through other body fluids and contaminated clothing or bed linen. Smallpox is highly contagious, and people who have it are most infectious during the first week of illness.
Q. What are the symptoms of smallpox?
A. The first symptoms of smallpox usually appear between a week and 17 days after exposure to the virus, and can include high fever, fatigue, headaches, backaches, and vomiting. The next symptom, which appears in the next two to three days, is a rash on the face, arms, legs and other areas of the body. The rash turns into raised bumps that become pus-filled blisters. Scabs develop and usually fall off three to four weeks later.
Q. How dangerous is smallpox?
A. The CDC classifies smallpox as a Category A agent, a designation given to diseases believed to pose the greatest threat to public health. Anthrax, botulism, and plague are also in this category. Up to 30 percent of smallpox cases result in death, and the death rate can be higher in infants and small children. The remainder of people who contract smallpox recover, though they are often left with permanent scarring and sometimes blindness.
Q. How is smallpox treated?
A. No proven treatment exists. People with smallpox are given intravenous fluids and medicine to control fever and pain, and antibiotics are given to prevent or treat possible bacterial infections. Two treatments for smallpox--Vaccinia Immune Globulin (VIG) and cidofovir--are being studied and could be given under investigational new drug protocols.
Q. Who will be receiving the smallpox vaccine?
A. Under President Bush's smallpox plan, HHS is working with state and local governments to develop volunteer Smallpox Response Teams. The health-care and emergency workers who will serve on these teams--estimated at nearly half a million people--are being offered the vaccine. The Department of Defense will vaccinate some military and civilian personnel who might be deployed in high-risk areas. Dryvax, the currently licensed product, is the vaccine being used to inoculate smallpox response teams and U.S. troops.
The smallpox vaccine is not recommended for the general public at this time because the risks of the vaccine are currently thought to outweigh its benefits. HHS is working on a process to make smallpox vaccine available to adults who want to be vaccinated. Sufficient supplies of a licensed vaccine are not available for the general public yet, and won't be available until approximately 2004. Members of the general public who choose to be vaccinated now would be vaccinated with an investigational vaccine.
Q. How is the smallpox vaccine given?
A. The smallpox vaccine is not given through a shot. A two-pronged (bifurcated) needle with a droplet of the vaccine is used to prick the skin several times in the upper arm. A red, itchy sore spot at the site of the vaccination within 3-4 days is proof that the inoculation was successful; that is, "it took." A blister develops at the vaccination site and then dries up. A scab falls off in the third week, leaving a small scar.
Q. How effective is the smallpox vaccine?
A. The smallpox vaccine has been proven to be highly effective. The first dose protects against the disease for three to five years, possibly longer. For people who haven't been inoculated who are exposed to smallpox, getting vaccinated within four days of exposure may prevent or lessen the severity of the disease in most people. Effective smallpox inoculation led to the global eradication of smallpox in 1980.
Q. What if you have already been inoculated?
A. People who may have received the smallpox vaccine before 1972 are considered susceptible to the disease. Because the vaccine may only be protective for three years to five years, public health officials are assuming that these people are not protected.
Q. What are the risks of the smallpox vaccine?
A. The smallpox vaccine is made from a virus called vaccinia, which is related to the smallpox virus. It provides immunity against smallpox, but it does not cause smallpox. The vaccinia virus is a live virus that has in the past grown on the skin of calves, sheep, and water buffalo. Dryvax was grown on the skin of calves. Because the virus is live, it is possible to get infected with vaccinia at a site other than the site of vaccination. People who get vaccinated must care for the site properly. Failure to care for the site, such as improperly disposing of bandages, could result in passing vaccinia to other parts of the body or to other people.
The most common side effects from the smallpox vaccine are a sore arm, fever, and body aches. People who get the vaccine should understand potential problems that could occur. Reactions to the vaccine have ranged from mild rashes to rare fatal brain inflammation (encephalitis). In the past, it was estimated that out of every million who received the smallpox vaccine, between one and two people died as a result of a reaction to the vaccine.
Relative to the disease, the smallpox vaccine is very safe. However, some people are at increased risk for complications. People at risk include those with eczema or other skin conditions, pregnant women (the fetus is at increased risk), people with immunodeficiency diseases such as HIV infection, and those with suppressed immune systems, which occurs in people with leukemia, lymphoma, generalized malignancy, or following solid organ transplantation. The CDC will report summaries indicating how many people have been vaccinated and the nature of any adverse events.
Smallpox Vaccine Guidance for Blood Industry
The FDA has issued guidance for the blood industry regarding potential blood donors who have recently received the smallpox vaccine (vaccinia virus) or those who may have had other direct exposure to smallpox vaccines. The recommendations were developed with smallpox experts at the Centers for Disease Control and Prevention and the U.S. Department of Defense. The FDA issued the guidance as a precautionary measure because the presence of vaccinia virus in transfused blood or plasma could be harmful to some recipients.
Reprinted from FDA Consumer. This article originally appeared in the March-April 2003 FDA Consumer.
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