Vaccines: Are You Hiding In The Herd?

Nov 12, 2013

Herd, as in "herd immunity," the concept being that the majority of vaccinated people protect the minority who aren't vaccinated, a kind of safety-in-numbers for your immune system. But what if the number in the minority starts to creep up?

RI child immunization rates, 2011. Click to enlarge.
Credit RI Dept. of Health / CDC, National Immunization Survey

That's what's happening in Western Mass., according to my friend and colleague Karen Brown of New England Public Radio. You can listen to her story on NEPR here or read a print version in the Globe here. After a couple of measles cases popped up in Boston recently, she says, public health officials highlighted the rising number of kids going without or delaying vaccines in the state's Western half as a risk for more disease outbreaks.

Brown does a great job explaining why some parents think they're making an educated, compassionate decision to refuse vaccines for their kids, but they're misinformed - and likely doing more harm than good. First, there's no known link between vaccines and autism. And as for the recommended schedule of immunizations for kids? Brown writes:

"The American Academy of Pediatrics and the Centers for Disease Control and Prevention, among others, have vouched for the safety of today’s vaccine regimen, and insist vaccines are neither toxic at the doses given nor taxing to normal immune systems."

As one of her experts tells her, many of the diseases we've nearly wiped out with vaccines are still:

"'...only a plane ride away. And every year the number of kids getting exempted (from vaccines) grows,” said Dr. Lawrence Madoff, director of Epidemiology and Immunization for Massachusetts. “When immunization rates fall, it doesn’t take long, even in a developed country, for diseases to resurge.”

(Case in point: the resurgence of polio in Syria.) Brown's sources point out the irony in the fact that, in some low-income neighborhoods, kids are missing vaccines because of spotty access to health care, while in well-off, well-educated communities, some parents refuse vaccines because they feel more empowered to question medical authority.

In Rhode Island, we've seen a growing number of pertussis (whooping cough) outbreaks, which could be down to a few reasons. First, pertussis isn't that unusual, and the vaccine isn't 100% effective, although health experts say it's far safer to be vaccinated than not, especially if you're going to be around a newborn. Second, scientists are finding good evidence (such as this study recently published in JAMA) that the pertussis vaccine loses efficacy over time. So the CDC recommends kids and adults stay up-to-date on the vaccine throughout a lifetime. Third, could we be seeing a rising number of Rhode Island parents refusing to vaccinate their kids? I'm not sure about the trend line, but in the chart above from the RI Dept. of Health, you can see that Rhode Island is slightly below the national average for the DTap (which includes pertussis protection) vaccine.