What Pertussis Epidemic?  

There has been a lot of news this year about pertussis, or whooping cough.  We have seen a spike in the number of cases of pertussis in California and a number of infant deaths from the disease.  It is assumed that the primary route of transmission to infants is via unvaccinated or out of date vaccinations of parents, caregivers and family members.  Until now, the CDC recommended infants and young children be vaccinated with three doses before they were 5 years old.  Until that third dose, they don’t have adequate immunity.  But, there was not a recommendation about teens and adults getting boosters.  It is unclear for how long the vaccinations confer immunity.  There is also a controversy swirling around about the possible link between vaccinations and autism.  I recently learned that the original study that showed this link selected specifically for autistic children, then determined what vaccinations they’d had.  So, the causality is fairly suspect.  But, this information circulates all over the Internet and shows up on many, many blogs.

Here are some of the problems with understanding this issue.

First, How many people have pertussis (incidence and prevalence)? We don’t know.  Cases of pertussis are reported but only if they are diagnosed.  This means that the patient has to have seen a healthcare provider and received a definitive diagnoses.  This is likely only if they had a case severe enough to be tested, or been hospitalized, or had a fatal case.  Many people may have whooping cough but not know it.

Second, How many people have been vaccinated?  We don’t know.  Only childhood immunizations are reported to the state health department and from there to the CDC.  Since childhood immunizations are required by schools, we have a decent source of information.  Once the child is enrolled in high school however, there is no more data on them.  Some workplaces require immunization data, particularly if you work for a healthcare organization or school.  But, many more employers do not require this.

Third, How do people get their information about vaccinations?  Blogs, CDC, public health departments, doctors, nurses, the news?  We don’t really know who is accessing which source, or what makes a consumer act on the information they find.  How do they know it’s credible?  When I google blog searched on “pertussis,” the first five links were:  California Healthline, Pathofilia (for the love of disease), CureTalk (a clinic trial recruitment site), BlogHer, and Sounds of Pertussis (pharmaceutical company Sanofi-Pasteur).   Like many consumers, I didn’t bother scrolling past these.

I really wonder how anyone could make an informed decision about this issue given the lack of information and tools with which to analyze it.  This is why we need public health informaticians!