Coming Your Way
Smallpox and Vaccination in the 21^st Century
Charles Grose, MD, Professor and Director of Infectious Disease
Department of Pediatrics, University of Iowa Hospitals and Clinics
Winter 2002

People in the Middle Ages identified three pox illnesses:

• "Small" pox was vaccinia, the same smallpox that we know today.
• "Large" pox is thought to have been syphilis, a much more virulent disease in the past.
• "Chicken" pox, a name derived from middle French pois chiche (chickpeas), was our varicella.

Smallpox, a life-threatening illness with a fatality rate of 10-20%, continued through the early 20^th century. Then a massive, worldwide effort was undertaken, and in the 1960-70s, this disease was eradicated. But the vaccination of healthy children was not without risk. Every year from seven to nine small children in the US died from complications directly related to vaccination. Children with immunosuppressive disease who were vaccinated in error would almost invariably die. For these reasons, routine childhood vaccinia vaccination was discontinued in the 1970s.

The eradication campaign was successful because there was a potent vaccine. Today, it is a lyophilized (rapidly frozen and then dehydrated under high vacuum conditions) preparation of live vaccinia virus. After eradication of smallpox, vaccine production ended except for a limited use with military personnel. In the year 2002, all people in the United States who have never received vaccinia vaccine are susceptible to smallpox. Older individuals who were vaccinated during childhood (before 1970) may have some residual immune protection.

With the advent of bioterrorism, such as that using anthrax this fall, concerns have increased about the intentional release of smallpox virus in the general population. As a direct result, the federal government has expressed a renewed interest in smallpox vaccination. Pharmaceutical companies are producing more of the traditional vaccine. In addition, they are also developing new smallpox vaccine products.

The traditional vaccine is produced using calf lymph. One of the new vaccine products is being prepared in human cell cultures, in a manner similar to that used in the preparation of rubella vaccine. Because it is produced in human cell cultures, it will probably causes fewer reactions, and thus fewer deaths. Phase 1 vaccine trials are being designed to evaluate the safety and effectiveness of these newer candidate vaccines.

If these clinical trials are successful, the pediatric community will be asked again to consider universal vaccination for smallpox. One strategy may include immunization only of 4-6 year old children, to avoid vaccination of younger children with as yet undiagnosed immunosuppressive conditions. In addition to vaccination, antiviral medications are also being developed to treat vaccinia virus infection.