Measles, Whooping Cough, and the Musk Ox

Mavenites, there have been reports in the news recently of unprecedented numbers of cases of measles in California, New York, and Ohio and a whooping cough epidemic has been declared in California. What is the reason for these outbreaks, the likes of which have not been seen in many decades?

Well, one thing is to blame:

No, no, not JUST she-who-will-not-be-named, but the general reduction in herd immunity due in large part to the anti-vaxx movement.

When I think of herd immunity, I think of the musk ox (see featured image). When the herd is threatened, adult musk oxen form a circle around their young to protect them. This wall of fur and flesh with pointy horns facing outward is an effective barrier against threats to the vulnerable young in the center of the circle. If you were to remove some of these barriers, the herd would become compromised and susceptible to attack. This is what is happening when vaccination rates drop – the wall of protection afforded by the majority of the population being vaccinated is reduced, and diseases like measles and whooping cough gain a foothold in the community, and the most vulnerable, especially infants from birth to six months who cannot be vaccinated against measles and diphtheria are at risk.

But is it just the reduction of herd immunity that is to blame for these outbreaks? Not entirely, especially not in the case of whooping cough. A recent report shows that 85% of the cases of whooping cough in San Diego were among patients who had received their full set of vaccines. What the monkey?

It’s true. Now, before the anti-vaxxers point their fingers and say “Nee-ner, nee-ner, nee-ner, we told you so!” Here’s what’s going on: The first pertussis vaccine developed in the 1940s was prepared from whole Bordetella pertussis organisms, and was successful in reducing the number of cases and deaths. Unfortunately, this whole-cell formulation combined with the diphtheria and tetanus toxoids (DTP) caused severe side effects such as localized reactions, fever, and convulsions. Because the vaccine coverage was so effective and the number of cases of whooping cough had been reduced so efficiently, the formulation was changed to a safer acellular form of B. pertussis (DTaP) in the 1990s, and was adopted for all five doses of the recommended vaccine and boosters. In 2010, outbreaks of whooping cough began to be reported at the highest rates since the 1950s. According to the study by the New England Journal of Medicine referenced above, immunity to the acellular version of the vaccine begins to wane 5 – 6 years after the final vaccination. Quoting the study:

“The incidence of pertussis was highest among the population of children who were 8 to 11 years of age and who had received the full five-dose series of DTaP in childhood, suggesting that the waning efficacy of the fifth dose among school-age children played a key role in both allowing and sustaining the recent pertussis outbreak.”

As a result of these findings, the CDC now recommends a Tdap booster beginning at 11 years of age.

Are the anti-vaxxers to blame for these unprecedented outbreaks of measles and whooping cough? Yes, but not entirely. The waning efficacy of the DTaP vaccine combined with the reduction in herd immunity has allowed whooping cough to regain a hold in the community. Mavenites, it’s time to take a lesson from the musk ox and circle around the weak and vulnerable in our population by boosting the immunity of the herd. Make sure you and yours are vaccinated and boosted.

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