Author: Rashi Venkataraman
Institution: Carnegie Mellon University
Date: July 2007
Researchers at the Washington School of Medicine in St. Louis recently developed a way to predict if a smallpox vaccine will result in an adverse reaction. This new development will not only help those that receive the smallpox vaccine, but may also improve the safety of other popular vaccines.
Considered a similar-pathogen-live vaccine, the smallpox vaccine is extracted from cowpox-infected cows, treated to remove contaminants, and then injected into patients. Because it is still "live" post-injection, the cowpox virus (very similar to smallpox) invades the body and triggers the immune system to mount a response. Memory B and T cells that "remember" what the disease looks like are released into the bloodstream so that if encountered with the virus again, the immune system will quickly mount a fast response. Unfortunately, the smallpox vaccination is not foolproof. Of those who are vaccinated for the first time, 15% develop a fever of 99°F or more. A study conducted by the Centers of Disease Control in 1968 found that close to 70 people in one million suffered serious reaction including erythema multiforme, generalized vaccinia, and even death.
Samuel Stanley Jr., M.D. leading the research team from Washington University found that genetic variations on our chromosomes are responsible for many of the side effects. Although Stanley admits that his team does not "know whether the same genetic variations we identified in our study are also linked to more serious vaccine complications," he concedes that the study "will point us in that direction in terms of looking for genetic alterations that predict more serious complications."
Stanley's team analyzed single nucleotide polymorphisms, or genetic variations, in nineteen genes that are linked to the body's immune response. Four of these genes had eight possible alterations that could be involved with the fevers that develop. Specifically, it is the IL-1 and IL-18 gene complexes on chromosome 2 that produce molecules known to stimulate fevers in the immune response.
In the U.S., the smallpox vaccine is mainly administered to high-risk groups, like healthcare workers or U.S. military personnel. However, other vaccines are more widely distributed. For example, federal law mandates that the MMR vaccine (which prevents mumps, measles, and rubella) is administered to all children. However, some children have suffered from seizures after receiving their vaccine. This discovery from the Washington School of Medicine could potentially help scientists develop tests to predict if a patient is at risk for vaccine-related reactions.
"Live-Attenuated Vaccines." World Health Organization.
"Making Vaccines: Similar-Pathogen Vaccine: smallpox virus." Nova Online. PBS.
- By Rashi Venkataraman