'Herd immunity' threatened in measles outbreak, pathologist says

The current concern over outbreaks of measles in the United States provides valuable lessons about how vaccinations are effective across a broad community. However, according to Gary W. Procop, MD, FCAP, a fellow of the College of American Pathologists, the spread of disease can be controlled only if a sufficient number of people in the community are vaccinated.

This phenomenon is called "herd immunity" or "community immunity," and here's how the Centers for Disease Control and Prevention (CDC) defines it:

." .. a situation in which a sufficient proportion of a population is immune to an infectious disease (through vaccination and/or prior illness) to make its spread from person to person unlikely. Even individuals not vaccinated (such as newborns and those with chronic illnesses) are offered some protection because the disease has little opportunity to spread within the community."

Dr. Procop is a professor and medical director of virology in the Pathology and Laboratory Medicine Institute at the Cleveland Clinic, as well as serving as medical director for enterprise test utilization and director of the parasitology and mycology laboratories.

Dr. Procop has a subspecialty in microbiology and chairs the CAP's Microbiology Resource Committee. He warns that the herd immunity can be disrupted.

"We see pockets of unvaccinated individuals, usually children, who are then susceptible to infection. Once an infection gets into that group, it's like a spark in tinder," Dr. Procop says.

"The real danger is that newborn babies or people with compromised immune systems who cannot generate a good antibody response to fight off the disease would suffer because of the decisions of the group who chooses not to get vaccinated," says Dr. Procop.

That some parents choose not to have their children vaccinated disappoints Dr. Procop.

"In many instances Americans will listen to television personalities rather than scientific opinion. As medical professionals we have to be vigilant, diagnose accurately and collaborate with our public health colleagues."

In recent months there has been media focus on whether the Ebola virus might spread beyond the few confirmed U.S. cases. Dr. Procop thinks the attention is misplaced. "The real risk of Ebola was extremely low. The risk of measles in the populations that are not vaccinated is much greater than the risk of ever getting Ebola."

To protect yourself and your children, follow the current vaccine guidelines. "If you are vaccinated, you will either not get the disease, or if you do get the disease, it won't be very serious," says Dr. Procop.

International travelers can learn about local diseases and recommended vaccines from in CDC Health Information for International Travel (commonly called the "Yellow Book") published by the Centers for Disease Control.