Unvaccinated Americans Continue to Pose Measles Risk


Researchers have found that lower vaccination rates in the US could explain a worrisome trend: One in eight US children are not protected against measles, a highly contagious disease, and up to a quarter of kids under the age of three are vulnerable to measles.

Emily Willingham of HealthDay quotes Dr. David Kimberlin, a professor of pediatric infectious diseases at the University of Alabama at Birmingham, who was not involved in the study, on the importance of the findings:

“We simply cannot take our eye off of this disease. These new data show that we have not done as well with this as we should.”

The results of a national survey of immunizations among US adolescents for the years 2008 to 2013 were analyzed by lead author Robert Bednarczyk, an assistant professor of global health and epidemiology from the Rollins School of Public Health at Emory University in Atlanta, and his colleagues. The researchers found that of the approximately 70 million young people under the age of 17, nearly 9 million were not protected against measles. In some cases, there are children who cannot, for health reasons, be immunized, but others are simply unvaccinated or under-vaccinated.

The study was presented to the yearly meeting of infectious disease specialists at the Infectious Diseases Week in San Diego. Since the study has not yet been published in a peer-reviewed journal, its findings are considered preliminary.

In 2013, the disease was the cause of 400 deaths per day around the world, says the World Health Organization. Symptoms of the disease include a runny nose, fever, and a rash across the entire body. Measles is the most infectious disease that is able to be controlled by vaccine and is passed through the air by cough or sneeze. The risk of infection is increased by the fact that a person can have the disease before presenting any symptoms, says the CDC.

In order for the disease to be controlled, at least 92% of the human “herd” needs immunity, with “herd immunity” referring to the zone created around immunized people. Some people such as infants cannot be immunized, and a child must be a year old before the two-shot series of the measles-mumps-rubella vaccine can be given. Preschool kids have the lowest immunity levels, and elementary children vacillate around 92%, which worries Kimberlin.

“Right now, in the older ages, we see immunity levels greater than 92 percent, which should be adequate to prevent sustained measles transmission,” said Bednarczyk, “but we do not have a very wide buffer.”

The CDC reports that measles travels into the US via individuals who have been exposed in other countries, most of whom have not been vaccinated.

Measles outbreaks linked to Disneyland infected 147 US citizens, and event that brought a renewed focus to the debate over vaccinating children. Small groups typically of wealthy parents sprinkled across the country refuse to have, or delay having, their children vaccinated, which can potentially allow outbreaks of the disease, writes NBC News’ Maggie Fox. This year alone there have been 189 cases of measles in the US. This number includes a woman’s death in Washington state.

Bednarczyk says the vaccine is very safe, and not vaccinating “is highly risky.” Rachael Rettner, reporting for LiveScience, writes that 5% of 17 year-olds in the US have never been vaccinated, according to researchers.

Another reason that some children are not receiving the vaccine is that some young people have an immune system condition that could prevent them from responding to the vaccine in the correct way. However, infants under the age of 6 months have a level of immunity because of their mothers’ antibodies.

There are also serious complications that can occur from having been infected by the measles virus, such as pneumonia and brain inflammation. Up to one-quarter of children who are infected by measles are hospitalized.

“It is frustrating to admit children to hospitals with a disease that is very preventable,” said Dr. Matthew Zahn, medical director of epidemiology at Orange County Health Care Agency in California. Zahn’s county experienced 35 cases of measles during the outbreak. “It is sobering to recognize that one exposure event can cause so many public health ripples around the country,” he said.

The CDC reports that measles was declared eliminated in the US in 2000. Then, in 2014, 668 cases were reported and a multi-state outbreak originating in Disneyland at the beginning of this year affected over 100, according to Ashley Welch of CBS News.

Thursday, a case of measles was reported in Fairfax, Virginia, and the child may have infected others. The CDC stated that the child had received the first dose of the measles vaccine, but had not yet received the second dose.