In 2010, California experienced the worst whooping cough outbreak in more than 60 years. The state reported 9,120 cases — which represented a third of all pertussis cases in the entire country that year — and 10 deaths. And now, after conducting an analysis of the California residents who refused to vaccinate their kids in the lead-up to that outbreak, researchers believe that persistent vaccine denial played a big role in allowing the illness to spread.
Researchers examined the non-medical vaccine exemptions for the children entering kindergarten between 2005 and 2010, and compared that data to the pertussis cases that were diagnosed in 2010. They identified 39 geographical clusters in the state with high rates of non-medical exemptions, and two clusters where the whooping cough cases were concentrated. And those two types of clusters tended to overlap.
Parents who chose not to get their kids vaccinated likely represented “one of several factors in the 2010 California pertussis resurgence,” the researchers concluded. Public health officials also suspect that whooping cough may be resurging because the vaccine typically used against it is becoming less effective over time.
In conclusion to their study, researchers warn that failing to immunize kids against pertussis ultimately leads to communities with lower-than-average vaccination rates — which allows whooping cough to easily spread, and puts infants at risk for contracting the potentially deadly disease.
California state law allows parents to opt out of vaccinations if they violate their beliefs, even if they don’t cite specific religious reasons for that decision. Last year, Gov. Jerry Brown (D) approved a law that will require parents who opt out of immunizations to sign a paper noting that they understand the “risks and benefits” of vaccines.
California parents aren’t alone. Across the country, persistent vaccine misinformation — like the widely-debunked myth that some types of vaccines can cause autism — has left many U.S. parents with lingering doubts about whether it’s safe to immunize their children. Officials from the Centers for Disease Control continually urge parents to make sure their kids get their shots. But even though most of the United States has high rates of vaccination, pockets of unvaccinated people can still allow diseases to spread rapidly. Federal health officials recently warned that measles, a disease that has practically been eradicated with the advance of vaccines, is making a comeback thanks to anti-vaccine beliefs.
And since 2010, whooping cough has continued to be a problem. Last year, the country faced the worst whooping cough outbreak in decades. This month, Texas is facing its own record-breaking pertussis epidemic.