The decision to begin widespread vaccination for smallpox, starting with 500,000 military personnel and an equal number of "first-responder" health-care workers, will probably cause a few hundred serious adverse reactions and perhaps some deaths -- a dark side of vaccination unseen in the world for 25 years.
Most people tolerate the smallpox vaccine with only minor effects, such as fever and body aches. But a survey of those inoculated in 1968 found about 1 person per million died of the vaccine's side effects, and as many as 52 of every million people suffered life-threatening reactions, including fever, serious infections and brain swelling.
The side effects are viewed by most public health experts as an acceptable trade-off against smallpox itself, which kills about 30% of its victims. And according to a national survey released Wednesday, most Americans agree. In the poll conducted for the Robert Wood Johnson Foundation, 65% of respondents said they would take the smallpox vaccine -- up from 59% polled in May. Only 22% said they would refuse the vaccine, down from 33% in May. However, pollsters did not offer details about the vaccine's risks.
For three millenniums before its eradication, smallpox regularly ravaged nations across the globe, killing millions with high fevers and an excruciating blanket of erupting pustules across the entire body, including the palms, eyelids and inside the nostrils. Survivors were often left with horrific scars as a lifelong reminder.
The last known case of smallpox occurred in Somalia in 1977. After a global vaccination campaign, the disease -- caused by the variola virus -- was declared eradicated in 1980. In this country, routine smallpox vaccination was ended in 1972, meaning that most people who were inoculated before that time have long since lost their immunity to the disease and would need to be reinoculated. Today's vaccine is derived from stockpiles frozen for decades.
Produced From Calves
The smallpox vaccine is made from vaccinia, a virus related to the variola virus but far less dangerous. The vaccine is mass-produced in cultures of lymph cells from calves.
Vaccination involves dipping a two-pronged needle into the vaccine, then using it to make 30 shallow skin punctures on the upper arm. In most cases this causes a red, itchy bump that eventually forms a pus-filled blister that heals in about three weeks.
The inoculation gives full immunity for three to five years but gradually wears off over the next decade, according to the federal Centers for Disease Control and Prevention in Atlanta.
Among the most serious side effects of the vaccine is a skin infection known as progressive vaccinia. The disease, which kills tissue around the vaccination site and can spread to other parts of the body, affects 1 to 2 people per 1 million vaccinations.
A more common but still serious reaction is a similar skin infection known as eczema vaccinatum. The infection causes a painful rash across the body and can be fatal. The problem occurs in about 39 cases out of every 1 million vaccinations.
Other Side Effects
Another serious side effect is post-vaccinial encephalitis, an infection that swells the brain, causing headaches, vomiting, high fevers and, in rare cases, paralysis and death. It affects about 12 people per 1 million vaccinations.
In addition to these side effects, the 1968 study found that about 935 of every 1 million first-time vaccinations result in serious but not life-threatening infections -- particularly on the face, eyelids or genitals.
All of these side effects are less common among people who were previously vaccinated for smallpox. Virtually no Americans under the age of 25 -- about 97 million people born after the date of eradication -- have been vaccinated.
Some of the side effects, including eczema vaccinatum, progressive vaccinia and the less serious generalized vaccinia, can be treated with vaccinia immune globulin -- a vaccine derived from the antibody-rich blood plasma of recently inoculated donors. It must be injected into muscle tissue. Severe cases can require massive doses -- as much as a liter injected into multiple muscles for a 220-pound person. Only 700 doses of vaccinia immune globulin are available, enough to treat cases expected from no more than 6 million vaccinations, according to the CDC.
Researchers are working to expand that supply within a few months, using a new vaccinia immune globulin formulation that can be administered intravenously in much lower doses. The antiviral drug cidofovir has also shown experimental promise for treating vaccinia infections, but it would be used only when vaccinia immune globulin is not available.