Whooping cough vaccinations

If you have a sixth grader, you may have gotten a reminder last spring (or will get one this fall) that they need a DTaP (diphtheria, tetanus, and pertussis) booster for your child. Here's why:

In the late 1990s, the Food and Drug Administration approved a new formulation, called DTaP, for babies and children. Before this, the vaccine used dead whole cells of pertussis to stimulate kids’ immune systems. Now the newer version deployed only a few selected compounds, not cells. The good news is that it hasn’t caused as many side effects. Early clinical trials suggested that this newer, acellular vaccine was also highly effective.But as Tom Clark, a pertussis expert at the CDC, told me, the studies fell short. They tended not to follow children for a long enough time. Or they defined cases in a way that missed milder infections. As a result, the studies missed a dire fact: The new vaccine doesn’t actually work for as long as the old one.Now we’re feeling the painful effects. During the 2010 whooping-cough outbreak in California, the largest number of cases, age-wise, were infants under the age of 1. But a notable spike was also seen in kids aged 7 to 10, most of whom had received all of the recommended shots—at 2 months, 4 months, 6 months, 2 to 3 years, and 4 to 6 years of age. These kids were supposed to be safe. What’s more, their risk seemed to increase with age, with the 10-year-olds most likely to get sick. When the CDC picked up that pattern, it “leapt out at us,” Clark says. These were kids who hadn’t received any doses of the old, whole-cell vaccine, which had been phased out completely by 2000. So the uptick strongly suggested that the acellular vaccine’s effects were wearing off year-by-year as the kids got older—long before anyone had anticipated.

Pertussis, simply put, kills babies. It makes older kids dangerously ill (and sometimes kills them, too). We need herd immunity to keep those babies from getting it. This is why doctors are now recommending that adults also get boosters (even the older vaccine does wear off over time).