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Smallpox: Inoculation Could Spread Disease By Mike Nartker Global Security Newswire Healthy people inoculated with the smallpox vaccine (see GSN, Nov. 19) could possibly cause illness among others, especially patients with vulnerable immune systems, according to experts. “Yes, it is a possibility,” said a National Institutes of Health official. “As the ability to prolong life has increased greatly, there are more people who are immunocompromised than ever before.” The smallpox vaccine consists of a weakened—but still living—virus called vaccinia or cowpox, a close cousin to smallpox. It is the live factor that creates the risk for the virus to spread from healthy inoculated people to others if no precautions are taken. The chances of contracting the vaccinia virus would increase for a person with a weakened immune system, such as a chemotherapy patient or someone with AIDS or HIV, said Carole Heilman, director of the Microbiology and Infectious Disease Division of the National Institute of Allergy and Infectious Diseases. “Anyone who was immunocompromised would be at risk.” A person infected with vaccinia could suffer a wide range of effects. A 1968 assessment showed that symptoms could range from fever and malaise to death, Heilman said. The severity of the side effects depended, in part, on the extent that the person’s immune system was compromised, according to Heilman. “The spectrum of side effects is related to the spectrum of immunocompromised patients,” she said. People infected with vaccinia, however, would not develop full-blown smallpox, according to U.S. Centers for Disease Control and Prevention spokesman Curtis Allen. Instead they would suffer something akin to cowpox, according to Allen. A Simple Hug Could Spread Vaccinia The vaccinia virus would spread primarily through direct contact with the inoculation site before it healed, according to experts. For example, a child could become blind by touching the uncovered, inoculated site on a healthy person and then touching his or her eye, Allen said. Once an inoculated person had infected someone, further transmission from the infected person to others—called secondary transmission—would be very unlikely, according to Heilman. While no direct study on the issue has been conducted, the vaccinia virus is not hardy enough to survive long in the population, Heilman said. She added that a person infected with vaccinia would feel ill, or “too crappy,” to do much to spread the virus during its highly contagious phase. Since vaccinia spreads only through skin-to-skin contact, secondary transmission is possibile but not likely, said Philippe Chilade, medical director of the Whitman-Walker Clinic in Washington. The danger comes from inoculated people not being told about the risk of transmission, Chilade said. Can the Immunocompromised be Vaccinated? Scientists are developing new smallpox vaccines that lower the risk to immunocompromised patients, even to the point where they could receive the vaccine directly (see GSN, Nov. 14). “[There has been] a lot of interest in alternative vaccines that are safe as well as effective,” Heilman said. Some companies are developing vaccines based on a dead virus, which would make them safe enough to use on people with weakened immune systems. Other research has focused on modifying the current live vaccine to reduce its virulence even further, Heilman said. Researchers have also developed treatments for vaccinia infections. Federal health agencies have stockpiles of vaccinia immunoglobulin, a medicine that could be injected into a person infected with vaccinia to “sop up” the disease, Heilman said. Research on Smallpox Treatment Some researchers are also developing antiviral drugs, according to Heilman. One is called Cidofovire, which federal authorities keep on hand in the event that the immunoglobulin was ineffective. It has not been tested in humans, but has proven effective as a treatment in monkey pox models and other animal testing, Heilman said. She added that some researchers are working on antiviral drugs that could prove effective even against smallpox itself. “You wouldn’t feel obligated to vaccinate everyone [against smallpox] if you have good drugs,” Heilman said.
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