When the American Academy of Pediatrics’ committee on infectious diseases reconvened for the first time after September 11, 2001, bioterrorism was a topic. Several people had died after coming in contact with anthrax-laced letters, and there was concern that future attacks would involve smallpox. The committee needed a pediatrician to serve as a liaison between the academy and the Centers for Disease Control and Prevention (CDC) in discussions of smallpox.

Robert S. Baltimore, M.D., volunteered and has since found himself the academy’s main spokesman on the topic.

“I had no idea what I was in for,” said Baltimore, professor of pediatrics and epidemiology, sitting in his office at the School of Medicine. Although he specializes in pediatric infectious diseases, Baltimore, like his peers in the academy, had no specific experience with smallpox. The virus had not been seen in the United States since 1949, when Baltimore was in grade school. His own research focuses on infections in newborns and hospital-acquired infections, and Baltimore studied smallpox only generally as an infectious diseases fellow in the 1970s at the Walter Reed Army Medical Center and the Army Institute of Research.

So Baltimore started educating himself, reading about the virus and collecting a grim photo archive on his computer showing the effects of smallpox on children. He had help from colleagues in the department’s infectious diseases division, who met every two weeks throughout 2002 to discuss bioterror-related topics in their journal club. “The group wanted to make sure we had a very detailed knowledge,” Baltimore said.

As the academy’s representative, Baltimore holds conference calls with the CDC’s “smallpox working group” and travels to Atlanta for CDC meetings. In addition, he has become embroiled in the debate over how best to vaccinate the public in the event of an attack. At issue are competing proposals of mass vs. “ring” vaccination—whether to inoculate everyone, or just those in the vicinity of people infected.

In the fall, CDC officials were moving away from the center’s earlier support for a ring vaccination strategy and recommended making the vaccine available to the general public. [As Yale Medicine went to press President Bush announced plans to inoculate up to 500,000 frontline troops and 10 million civilian health care and emergency workers against smallpox, but advised against vaccination for the general public at this time.] Baltimore thinks mass vaccination would be a mistake, and on behalf of the academy has advocated the alternate approach. Children are more susceptible than adults to serious complications, he said. And there is the worry that individuals who avoid vaccination for health reasons might be exposed to the live vaccinia virus anyway, through contact with those who have been vaccinated.

There are three situations in which the vaccine could be fatal. In people with certain skin conditions, including eczema, the vaccine can spread, causing pustules to form over the entire body. Those with immune systems compromised by aids or chemotherapy, for example, may also become seriously ill from the vaccine. And in rare cases, some of those vaccinated will develop oozing, infected sores in the injection site that spread and invade deep tissues without healing.

In the first two instances, said Baltimore, children are more at risk. Many skin disorders disappear with adulthood, which means more children have them, and immune deficiency may not be apparent in young children.

For adults, the fatality rate for smallpox vaccine is about one per million. For infants, the rate is about 5 per million and there are serious adverse reactions in about 400 per million—a rate that decreases with age. The CDC has the antidote for severe reactions, an antibody-rich blood product known as vaccinia immune globulin, but current quantities are minuscule. Baltimore also is concerned about the vaccine itself. The CDC is diluting stockpiles of the old vaccine to stretch it while new vaccine is manufactured. But neither the diluted version nor the new one has been tested on children.

Even if at-risk children and adults are not inoculated, they can be infected through contact with people who have received or administered the vaccine and have it on their skin. “Mass vaccination carries with it risks that can’t be justified,” Baltimore said. “The information that all public health people have been given is that the chances of a smallpox outbreak are remote. Should there be additional information that says this isn’t true, we would say this should be reconsidered.”