Parents Should Vaccinate Against Pertussis, Oregon Health Officials Say

State officials sent out a reminder to parents Tuesday warning of the dangers of not vaccinating children against pertussis.

Pertussis, or whooping cough, is a highly contagious bacterial disease affecting 10,000 to 40,000 people in the U.S. annually, according to the Center for Disease Control. And although more than 90 percent of Oregon children are vaccinated, those who aren’t stand to spread the disease to other unvaccinated children at schools, churches, and other social gathering places –– effectively risking an outbreak, officials said.

According to Oregon Health Authority spokesman Jonathan Modie, a newly published report in "The Journal of Pediatrics" suggests that relaxing immunization recommendations and school requirements could cause vaccine-preventable diseases to spread.

The study, "The Timing of Pertussis Cases in Unvaccinated Children in an Outbreak Year: Oregon 2012," reviewed 351 reported pertussis cases among children 2 months to 10 years old living in 72 different northwest Oregon zip codes between January and November 2012. Of those 351 cases, 76 were for unvaccinated kids.

The study's authors, epidemiologists Steve Robison and Juventila Liko, learned a pertussis outbreak was three times more likely to affect unvaccinated children earlier than vaccinated kids, and the unvaccinated kids could then spread the disease more easily among other unvaccinated children.

The recent measles outbreaks in cities across the U.S. have sparked multiple studies by various agencies to find out what role unvaccinated children play in spreading preventable diseases in communities populated by other unvaccinated kids.

"Parents who are reluctant to immunize their children often have social networks and other connections to others with similar lack of immunizations," Robison said in a statement. "This may provide a way for infectious disease to spread across communities."

From the study:

In this study, young children who are not immunized tended to have pertussis 1-2 weeks before children who were immunized and living in the same zip code area, a result that would be expected if pertussis were spreading across the metropolitan area through social networks that had larger numbers of parents choosing to delay or avoid immunizations.
A consequence of this hypothesis as supported in this study is that deliberately children who are not immunized represent a dynamic risk of spreading disease in an outbreak, and have an impact that is greater than simply lessening overall community immunity levels.
Diseases such as pertussis may spread across areas through the choice of parents to not immunize or to limit immunizations. Once locally present, pertussis will spread to the unimmunized and vulnerable, who in turn through the weight of exposure may then ignite a wider outbreak in vaccinated populations.

The complete study can be found on The Journal of Pediatrics website.

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