Do You Need a Smallpox Shot?

Many Americans over age 50 bear the faint, dime-sized scars of long-forgotten childhood vaccinations against smallpox, a lethal disease eradicated years ago.

Now, decades later, the increased threat of attacks using biological agents like smallpox has raised questions over whether to resume vaccinations that can cause serious or even fatal complications.

Smallpox vaccinations were halted 30 years ago in the United States. But do those old inoculations offer any protection against the disease? Would they reduce the severity of side effects in those who are revaccinated? Are revaccinations safe for older people?

Old vaccinations and boosters have probably lost their protective powers, experts say.

"The good news is if you had a previous smallpox vaccination, any future vaccination will be less risky" because of residual immunity that reduces adverse effects, says C.J. Peters, M.D., director of the Biodefense Center at the University of Texas Medical Branch in Galveston.

"But," he cautions, "the older you are, the less efficient your immune system is," and that raises risks. In fact, the Centers for Disease Control and Prevention (CDC) advises people with weak immunity not to have vaccinations unless they are exposed to the disease. [See When You Should and Shouldn't Be Vaccinated.]

Nor does the agency even recommend inoculations for most healthy individuals unless an attack is imminent or a smallpox case detected. The vaccine will almost always prevent smallpox if given within three days of exposure.

The quandary for guardians of the public health arises because with no surefire treatment for smallpox, vaccinations remain the best defense. But the vaccination, using a live virus, causes reactions ranging from mild soreness to, in rare cases, brain inflammation and a lethal infection called progressive vaccinia.

Historically, of every 1 million people vaccinated, from 14 to 52 will fall seriously ill—and one or two will die, the CDC reports.

But the odds of dying from the disease—about 30 percent of patients don't recover—are far higher than dying from the vaccine. Spread by direct contact, the smallpox virus is most contagious when a rash appears, developing into little blisters that fill with pus, pop and leave scabs.

Smallpox inoculations are mandatory for U.S. military personnel but voluntary for 11 million health and emergency workers. In January the CDC began shipping vaccine to 400,000 "first responders," workers who would tend the infected.

The reaction has been mixed. A New York Times survey found that about 350 hospitals decided not to inoculate their workers because of potential side effects, the fear of spreading the virus to patients and others and the lack of compensation for those hurt by the vaccine.

Even though vaccinations are not being given to the general public, CDC spokesman Curtis Allen says the government is setting up a process to accommodate those who insist on being vaccinated.

Made from the vaccinia virus, the vaccine is pricked into the skin with a two-pronged needle. Within days a blister appears, and a scab forms within three weeks. Until the site heals, it's possible to transmit smallpox to others or to other parts of the body. "If you inadvertently touch the area, and then another, you'll have another lesion,'' says David Pegues, M.D., associate professor of infectious diseases at the University of California at Los Angeles.

What happens if smallpox is detected? Vaccinations could be given in a ringlike fashion around the area where it occurred to prevent further spread, says Charles Ericsson, M.D., head of clinical infectious diseases at the University of Texas at Houston.

"That's when it's time," he adds, "for the public to be inoculated."

Michele Meyer is a freelance health writer in Texas.