Unvaccinated Children at Much Greater Risk for Whooping Cough

Whooping cough, known medically as pertussis, is a highly contagious infection of the respiratory system that is marked by severe coughing spells that end in a “whooping” sound when the person breathes in. Before a vaccine was available, whooping cough was a major cause of childhood illness and death in the U.S., but
with the introduction of a vaccine in the 1940s, the number of cases fell from approximately 200,000 a year to an all-time low of 1,010 in 1976. Since then, however, the number of whooping cough cases has been steadily increasing, reaching 25,827 in 2004; the highest since 1959. Experts believe this trend could be due in part to the rising number of parents who refuse some or all of the recommended immunizations for their children—a theory confirmed by a recent study.

To get a better idea of the impact immunization refusal has had on whooping cough, Dr. Jason Glanz and colleagues analyzed the records of children 2 months to 18 years enrolled in the Kaiser Permanente Colorado health plan from 1996 to 2007. They looked for children who had laboratory-confirmed cases of whooping cough, and for those whose parents had refused at least one of the initial series of DPT—diphtheria, pertussis, and tetanus—immunizations for nonmedical reasons. The researchers found that unvaccinated children were 23 times more likely to get the infection than those who received the full course of immunizations.

Additionally, a second analysis of 27,748 children from 2 to 20 months of age who were continuously enrolled at Kaiser Permanente, there was a similarly high risk of infection among the children of parents who refused the vaccine. “This study helps dispel one of the commonly held beliefs among vaccine-refusing parents: that their children are not at risk for vaccine-preventable diseases,” Dr. Glanz said. “It also shows that the decision to refuse immunizations could have important ramifications for the health of the entire community. Based on our analysis, we found that 1 in 10 additional whooping cough infections could have been prevented by immunization.”

While the study did not examine the reasons why parents refused to have their children vaccinated, the researchers say it could be because as many vaccine-preventable diseases, such as whooping cough, polio and smallpox, become rarer, parents are shifting their focus from disease prevention to issues of vaccine safety. Though numerous studies have found no link between vaccines and autism, the fear is still prompting some parents to refuse vaccinations. Other parents believe their children are at low risk for infection and that many diseases aren’t a severe enough threat to their children’s health. “These findings stress the need to further understand why parents refuse immunizations and to develop strategies for conveying the risks and benefits of immunizations to parents more effectively,” the researchers write.

Dr. Gregory Poland, director of Mayo Clinic Vaccine Research Group in Rochester, Minnesota says the findings are consistent with other studies and agrees that “parents need to know they place their children at a documented and real risk, as well as others, when they refuse vaccines based on inaccurate information.” He added that “there is plenty of pertussis out there and it is highly contagious.”

The bacteria spread from person to person through tiny drops of fluid from an infected person’s nose or mouth. These may become airborne when the person coughs, sneezes, or laughs. Others then can become infected by inhaling the drops or getting the drops on their hands and then touching their mouths or noses. Experts believe that up to 80 percent of non-immunized family members will develop whooping cough if they live in the same house with someone who has the infection.

Dr. Glanz and his colleagues say they are concerned that the decreased immunization rates could also lead to other disease outbreaks across the country. For instance, in 2008 there were 131 cases of measles, the most in 12 years.

The study will appear in the June 2009 issue of the journal Pediatrics.