By late summer 2010 an alarming number of children in California had developed pertussis, or whooping cough—five times as many as in the first half of 2009. David Witt, a physician and infectious disease specialist who works at Kaiser Permanente San Rafael Medical Center, cared for some of those sick children. His practice lies in the heart of Marin County, the famously counterculture spit of land north of San Francisco. At first, he assumed that the outbreak was a consequence of parents refusing vaccinations for their children. As the incidence continued to climb month after month, however—not just in northern California but all across the state—Witt began to wonder whether something else was going on.
Working with his college-age son Maxwell and his pediatrician colleague Paul Katz, Witt retrieved the records for 132 Kaiser Permanente patients younger than 18 who had tested positive for pertussis between March and October 2010.
“The bulk of the cases were in fully vaccinated children between eight and 12 years old,” Witt says. “That was a total surprise.”
As Witt's small study spotted, and larger ones have since confirmed, protection granted by the vaccine, which has been used for the past two decades, is wearing off much faster than public health planners anticipated. Rates of pertussis increased at least threefold between 2011 and 2012 in 21 states. Whereas some of these cases occurred among children who had never been vaccinated, most of the affected children had in fact received vaccines; those inoculations simply failed to safeguard them over the long term.
Now health authorities are scrambling to devise new strategies for protecting kids. There are no easy solutions. No one is developing a better vaccine to replace the current one. Attempting to recommend additional shots would trigger years of public health debate, and it is not clear whether extra doses of vaccine would make a difference. Even discussing the problem provokes uneasiness: with antivaccine sentiments and vaccine refusal at historic highs, nobody wants to impeach one of public health's crucial tools.
Before a vaccine became available in the 1940s, many parents learned firsthand that pertussis was a terrible disease. The bacterium that causes it, Bordetella pertussis, produces a toxin that damages the tiny sweeping hairs that coat the lining of the lungs, preventing them from clearing the airways of mucus and the microbial invaders. Following uncontrollable coughing fits—some of which are strong enough to cause seizures and brain damage—children wheeze and gasp for breath, giving the illness its name. In the pre-vaccine era, whooping cough afflicted as many as 200,000 children each year in the U.S. and killed about 8,000. The new vaccine shrank the incidence of pertussis from around 157 cases for every 100,000 members of the population to one in 100,000.
This success came at a cost, though. Researchers crafted the original pertussis vaccine from dead pertussis bacteria that could not reproduce but retained many microbial proteins by which immune cells could recognize and attack B. pertussis before it caused disease. Unfortunately, those whole-cell preparations also contained other molecular components that could cause unwanted immune system reactions, such as swelling near the injection site and, in rare cases, high fevers that could dangerously inflame the brain. “People didn't pay much attention to the reactions in the early days, because the death rate before the vaccine came along had been so staggering,” says James Cherry, a longtime professor of pediatrics and vaccine researcher at the David Geffen School of Medicine at U.C.L.A.
Over the next few decades, however, concern surrounding the vaccine's side effects intensified. In the 1970s Sweden and Japan ceased using the vaccine altogether. A government study published in England in 1981 concluded that the vaccine caused permanent brain damage once in every 310,000 doses (a result that was later disputed). And in 1982 an NBC broadcast aired criticisms of the vaccine, turning public opinion against it and jump-starting the U.S. antivaccine movement.