Accessibility links

US Military Study Says It's Safe to Conduct Large Smallpox Vaccination Campaign

A U.S. military study has found that a large smallpox vaccination campaign can be carried out safely with few adverse health consequences. The findings offer the first new data about the safety of smallpox vaccination in 35 years.

The U.S. government has been amassing smallpox vaccine to defend Americans against a possible attack by bioterrorsts dispersing the virus. But officials have lacked recent data showing what the vaccine's side effects are.

It had not been used in the United States for more than a generation - since soon after the virus was eradicated worldwide in the late 1970s. The most recent U.S. study of vaccine side effects was conducted in 1968 while smallpox inoculation was still going on. Officials wondered if differences in the population since then decreased the data's validity, especially since HIV has weakened the immune systems of many people.

Now, the U.S. Defense Department has released two studies of nearly half a million uniformed military personnel given smallpox vaccine since last December.

The top U.S. military health officer Dr. William Winkwerder says the results show few serious adverse reactions among them.

"Our experience demonstrates that a large-scale smallpox vaccination program can be conducted safely," he said.

The findings, published in the Journal of the American Medical Association, show that negative side effects occurred at lower rates than before. There was just one case of brain swelling, a rate of two per million, only about one-third the historical rate. Blistery skin rashes also showed up at one-third the old rate, or 80 per million. Heart inflammation was about four-fifths of the rate of a 1970s and '80s study in Finland, or 82 per million. No deaths occurred.

In fact, not more than three percent of vaccine recipients needed short term sick leave.

Another study overseer, U.S. Army Colonel John Grabenstein, attributes the improved results to greater patient selectivity and more care with smallpox inoculation than in the past.

"Our program implementation focused on human factors, how people behave staff training, screening for people who should not get the vaccine, education to the recipients about how they should act responsibly and they did, and their due attention to bandaging," he said.

Colonel Grabenstein says the military study is applicable to U.S. civil society because differences between the two populations are negligible.

But the government's top infectious disease expert warns public health officials not to become complacent about the smallpox vaccine's side effects. Dr. Anthony Fauci of the National Institutes of Health says the precautions the military doctors followed should be practiced with everyone.

"We cannot take this study to say that we're dealing with an absolutely safe vaccine," he said. "No. The vaccine has some severe adverse events associated with it. We need to realize that as we continue with the vaccination program in the civilian population as well as the continuation of it in the military population."

Nevertheless, the U.S. military studies reaffirm that, for a population, the smallpox vaccine is much safer than the virus, which kills 30 percent of its victims.