Why does whooping cough keep coming back?

Whooping cough, also known as pertussis, has remained one of pediatrics’ -- and parents’ -- most troublesome issues. The highly contagious bacterial disease, which leaves victims (traditionally children) with a hacking cough, can be fended off with a vaccine that has been in use for decades.

But in spite of the vaccine’s good work, say the authors of a study published online Monday in the journal Proceedings of the National Academy of Sciences, whooping cough cases have been on the rise over the last two decades. What was going on? Are people simply more aware and reporting more pertussis than they used to, or has the disease mutated into a different strain so that the vaccine no longer prevents it?

After designing a model based on the data, the researchers discovered that a third explanation was most likely: that as a herd, people have lost immunity, allowing the disease to reemerge. Unlike many vaccines, the pertussis vaccine doesn’t confer lifelong immunity. When whooping cough was more common, people as a group tended to be exposed and re-exposed to the disease more frequently as it jumped from person to person -- meaning that as a group, resistance was constantly kept pretty high.

Once the vaccine was implemented, however, whooping cough became, on a regular basis, less common. Good, right? The problem is that the less prevalent it is, the less likely people are to get booster shots. And the more time passes, the more the body “forgets” what to look out for, even after being vaccinated or after having suffered it before. So when a bad epidemic comes through years later, it can do some serious damage.

Moral of the story? The Tdap booster shot is your friend.

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