Pertussis, more commonly known as whooping cough, is making a major comeback across the U.S., the Centers for Disease Control and Prevention (CDC) announced on Thursday. Nearly 18,000 cases have been reported nationwide to the CDC in 2012, more than twice as many as were reported at this time last year. That puts the country on track for the most cases in more than 50 years.
“We may need to go back to 1959 to to find a year with this many cases reported,” said the CDC’s Dr. Anne Schuchat in a conference call.
Some areas of the country have been hit harder than others, such as Washington state, which declared a whooping cough epidemic in April. More than 3,000 cases have been reported in the state so far, compared with 20 reported by the same time last year, said Mary Selecky, secretary of the Washington State Department of Health. “For every case that we know about, we suspect that there are many people out there who have pertussis and don’t know it,” she said.
“What’s happening in Washington state is a reflection of the larger national picture of this very difficult to control disease,” said Schuchat.
The highest rates of infection are being seen in babies less than 12 months old; half of all cases are in those under 3 months old. That’s not surprising, since these infants are too young to be vaccinated. They are protected by mothers’ vaccination in pregnancy and the vaccination of other adults and children who come into contact with them — but vaccination rates aren’t as high as they should be.
The CDC notes also that pertussis rates are high in young kids and teens, aged 10 to 14. Health officials think the spike is due largely to the waning protection of pertussis vaccinations received earlier in childhood. The U.S. used to use a childhood pertussis vaccine known as DTwP that contained killed B. pertussis bacteria cells. But in 1997, in response to fears that the vaccine was linked with rare neurological problems (the connection has not been shown scientifically), manufacturers switched to a so-called acellular vaccine (DTaP) that uses proteins from the surface of the bacterium to trigger immunity.
DTaP is given in five doses in childhood, with the final dose given between ages 4 and 6. Although the vaccine offers strong protection soon after it is given, evidence suggest that protection peters out sooner than with the older vaccine — perhaps within five years. That’s why the CDC recommends a pertussis booster at age 11 or 12.
“Our pertussis vaccines are not perfect. They don’t provide protection for as long as we wish they would and this adds to our challenges during our times of increased disease,” said Schuchat. Still, children who have been vaccinated but catch whooping cough have less severe disease and are less infectious than unvaccinated children.
Pertussis is a contagious bacterial disease that causes uncontrollable, violent coughing. The coughing makes breathing difficult for suffers, often resulting in the deep “whooping” sound that characterizes the disease. It is particularly dangerous for young children and infants; half of babies who get the disease are hospitalized.
Rates of pertussis tend to be cyclical in nature, with peaks occurring every three to five years or so. The last peak occurred in 2010, when more than 27,000 cases and 27 deaths were reported. So far, this year, nine children have died. “We may be hitting one of those cycles where we are in an upswing around the country,” said Schuchat. However, the rates of disease in young teens are different from what the CDC has seen in the past, which is why health officials recommend the booster shot — and have debated moving up its timing.
Along with children, teens aged 11 to 18 and adults aged 19 to 64 are recommended to receive a pertussis vaccine (the booster shot, called Tdap). Adults and pregnant women who may come into contact with a baby under 1 are also strongly encouraged to get vaccinated with Tdap for the infants’ protection. Kids who don’t get vaccinated have an eight times higher risk of getting pertussis.
In 2010, 95% of 3-year-olds had received at least three doses of the DTaP vaccine, and 84% had had four doses. However, the number of kids and adults getting the booster shot were much lower. Sixty-nine percent of 13- to 17-year-olds had gotten Tdap and only 8% of adults had. “I know we can do better than this. We need to do better than this,” said Schuchat.