Jean Zahalka, a soft-spoken public health nurse with shortly cropped gray hair, sat in a small office at the headquarters of the Snohomish Health District, conducting a phone interview with the mother of a 7-month-old baby who had just been diagnosed with whooping cough.
Luckily, the little boy didn’t attend daycare, which meant that he hadn’t had many opportunities to infect others. And despite his persistent cough, he was holding up well, possibly because he’d already had two doses of DTaP, the childhood vaccine for diphtheria, tetanus, and pertussis.
But then the mom told Zahalka that the boy’s 3-year-old sister was also coughing. Zahalka winced. Next, it came to light that the mother’s 14-year-old niece had spent three days with the family earlier that week, which meant she was probably infected as well. The niece’s mother had just lost her job and could not afford to buy antibiotics, so the health department was going to have to cover the cost of her treatment in order to curb the spread of the infection.
As health departments across the country are coming to learn, it is extremely difficult to monitor and control pertussis outbreaks. For one thing, many cases go undetected. “We’re reporting just the tip of the iceberg,” says Sandi Paciotti, communicable disease manager at the Skagit County Health Department, which tallied the most pertussis cases in Washington State in 2012. Paciotti estimates that three to five times more people have been infected than are reflected in her official numbers.
One reason is that 15 percent of the Skagit County population is uninsured and unwilling to pay for the $300 test. Teens are another overlooked pertussis reservoir; the director of the Skagit County Health Department, Peter Browning, says his 13-year-old son caught pertussis early in the outbreak, but since he had been immunized, Browning didn’t suspect it. “We don’t stop loving our kids after age 13, but we don’t rush them to the doctor, either,” he says.
The vaccine’s effectiveness begins to drop
after one year. Five years after the final dose, it provides only 70 percent protection.
There are probably also thousands of adults who have suffered through the infection without seeking treatment. Adults who have been vaccinated, like Fikkert, often have milder symptoms, but they are still contagious. Some do go to the doctor but only after they have been sick for several weeks, at which point the test can come back negative even if they had the infection. And some doctors do not even consider pertussis when adults come in complaining of a persistent cough. “They don’t think adults can get it,” the CDC’s Martin says.
With an infection so difficult to control, the best hope is prevention. But a better vaccine may be years, if not decades, away. “We just don’t know what we should be targeting,” says Martin, pointing out that no one knows what parts of the bacterium should be included in the vaccine to make it more effective.
Scott Halperin, the director of the Canadian Center for Vaccinology in Halifax, believes that changing the immune-boosting chemicals, called adjuvants, in the vaccine could make a difference. Camille Locht, a microbiologist at Inserm and Institut Pasteur de Lille in France, is developing a live vaccine for newborns; he says it could give infants enough protection to survive until they get their childhood series, but so far he has tested the vaccine only in adults.
The CDC began recommending a tetanus, diphtheria, and pertussis (Tdap) booster shot for most people over age 11, including adults up to age 64, in 2005. But as of 2010, only 8 percent of the adult population had actually received one. Moreover, an ongoing CDC investigation suggests that, like the childhood vaccine, the adult Tdap booster lasts only a few years at most.
Yet with the exception of childbearing women, who are advised to get the booster during every pregnancy, Tdap is licensed only for one-time use in adults. “That probably isn’t enough,” says Amie Tidrington, the immunization clinic manager for the Skagit County Health Department.
Still, it is crucial to vaccinate as many people as possible, says Gary Goldbaum, the health officer of the Snohomish Health District in Everett. Unprotected people are much less likely to encounter the infection if most of the population is protected. Despite a slew of recent funding cuts, Goldbaum’s district has held 20 vaccination clinics since the outbreaks started.
Last spring the American Congress of Obstetricians and Gynecologists sent pertussis information packets to more than 33,000 of its members to increase awareness among doctors, and a joint program between the AmeriCares charity and pharmaceutical company Sanofi-Pasteur has given more than 117,000 free Tdap booster shots to health clinics around the country to immunize uninsured, low-income families. “If we are serious about trying to protect the most vulnerable,” Goldbaum says, “the rest of us have to be fully protected too."