The eradication of smallpox worldwide by 1980, largely due to massive immunization efforts, is a success story for vaccination and public health. The history of the rise and fall of smallpox is unique and interesting, but this once conquered disease is back in the public health spotlight with controversy over the smallpox vaccine.
Smallpox Vaccine
Smallpox is a disease that is fatal in 30% of unvaccinated people, caused by the variola virus, an orthopoxvirus. However, the smallpox vaccine is not made from the variola virus. The smallpox vaccine contains the live vaccinia virus, another member of the orthopoxvirus family. The smallpox vaccine does not cause smallpox, but it can cause a disease called vaccinia.
Prevention of Smallpox
Smallpox can be prevented with vaccination. In addition, vaccination up to 3 days after exposure will prevent smallpox or significantly reduce the symptoms and likelihood of death. Vaccination 4 to 7 days after exposure may still be helpful in reducing the severity of the symptoms.
Dryvax
The vaccine licensed by the FDA was taken from a weak strain of vaccinia virus called the New York City Board of Health strain. It was produced by Wyeth Laboratories and licensed under the name Dryvax. Wyeth stopped production in 1982.
Vaccination Site
The vaccine is given with a two-pronged needle that is used to prick the skin of the upper arm several times causing a few drops of blood. In 3-4 days a red, itchy bump forms. In the first week the bump develops into a blister, then fills with pus, and drains. In the second week, the blister dries up and begins to scab over. In the third week, the scab falls off, leaving a scar. For a few days after the vaccination, a person can get fever, chills, and swollen lymph nodes.
Smallpox Vaccine Needle - Closeup
Contagion of Vaccination Site
The immunization site is contagious until the scab dries up completely and falls off. Someone who comes in contact with the immunization site or bandages could get vaccinia, but not smallpox. Smallpox Vaccine - Spread to other sites
Side Effects of the Vaccine
There are side effects associated with smallpox vaccination. The majority of these are mild, and require no medical attention. However, there are serious side effects that require medical care. The following is a list of potential side effects of vaccination:
- Minor local reactions
- Minor generalized reactions
- Inoculation of other sites
- Generalized Vaccinia
- Eczema Vaccinatum
- Vaccinia Keratitis
- Progressive Vaccinia - Vaccinia Necrosum
- Post-Vaccinial Encephalitis
Death from Smallpox Immunization
Death occurring after smallpox immunization is most often caused by post-vaccinial encephalitis or progressive vaccinia. Prior to 1960, approximately 1 to 2 people out of every 1 million people vaccinated died.
Factors Affecting Risk of Side Effects
The estimated risk of developing side effects may not be accurate today for two reasons - immune suppression and previous immunization. On the one hand, the risk of side effects would be higher in people with suppressed immune systems from HIV/AIDS, or taking immune suppressing drugs for cancer or organ transplantation. There are more people in the United States today with suppressed immune systems than there were in 1960. On the other hand, the risk of side effects may be lower for people who have been vaccinated in the past.
Treatment of Side Effects
There are 2 medications that may help people who have certain serious reactions to the smallpox vaccine - Vaccinia Immune Globulin (VIG), and cidofovir. VIG is a product that contains antibodies that neutralize the vaccinia virus. It has been used in the past and felt to be effective for eczema vaccinatum, generalized vaccinia, and progressive vaccinia - but there are no controlled studies to prove this. By the end of December 2002 there will be enough VIG to take care of the predicted reactions if 27 million people are vaccinated. Cidofovir is an experimental antiviral drug that has shown activity against poxviruses in test tubes. By the end of December 2002 there will be enough cidofovir to treat the predicted reactions if 15 million people are vaccinated.
Information for this article was taken from
-Polgreen P, Helms C. Immunizations - Vaccines, biological warfare, and bioterrorism. Primary Care Clinics in Office Practice 01-Dec-2001; 28(4): 807-21, vii.
-Diven D. An overview of poxviruses. Journal of the American Academy of Dermatology 01-Jan-2001; 44(1): 1-16.
-Silvers M, Steptoe M. Immunizations - Historical overview of vaccines. Primary Care Clinics in Office Practice 01-Dec-2001; 28(4): 685-95, v.
-Centers for Disease Control Adverse Reactions Following Smallpox Vaccination
-Department of Health and Human Services Reactions After Smallpox Vaccination
