Whooping cough cases in the U.S. have more than doubled since last year and could be the worst since 1959, the Centers for Disease Control and Prevention said.
In its weekly Morbidity and Mortality Weekly Report, the agency focused on a pertussis epidemic in Washington state, where cases have increased by 1,300 percent from 2011 to 2012. By June 16 there were 2,520 cases, the highest number reported since 1942.
At a press briefing, Dr. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases, talked to reporters about the spread of the disease and why numbers have been going up. In Washington and the U.S., a growth in cases has been seen among infants under one year and children ages 10, 13 and 14.
“What is happening in Washington state is a reflection of the larger national picture,” she said, adding that the country may see record high pertussis rates this year. Nine deaths from whooping cough have been reported this year so far among roughly 18,000 cases that have reported to the CDC.
Schuchat said a number of factors are driving the increase. The disease is cyclical, she noted, with peaks and valleys that happen about every three to five years. Immunity to the vaccine could diminish over time. A rise in diagnoses and reporting of cases may influence the data as well.
Schuchat stopped short of blaming vaccine delayers and abstainers for the increase in cases. She said she’s aware of pockets around the country with large numbers of unvaccinated people, but added, “We don’t think (they) are driving this current wave. We think it is a bad thing that people aren’t getting vaccinated or exempting, but we cannot blame this wave on that phenomenon.”
Very young infants—those under two months—are especially vulnerable to pertussis since they’re too young for the vaccination. “Their protection instead depends on the immunity of the people around them,” Schuchat said, “especially pregnant women, their mothers. That is why we strongly urge pregnant women and all who will be around babies to be vaccinated.”
The rise in whooping cough cases among older children may be due, she added, to declining protection from the vaccine over time. In 1997 a switch was made in the immunization, from the whole cell to the acellular pertussis vaccine, which “might have done something to impact how long the vaccines last. “
The switch was made, Schuchat said, because the acellular vaccine had fewer side effects. The CDC recommends a pertussis booster called Tdap for children 11 to 12. However, in Washington, whooping cough rates among 13- and 14-year-olds is higher despite high rates of Tdap boosters.
The pertussis vaccine “remains the key single most effective approach to prevent infection,” she said. “It is critical to protect infants and others at high risk.” She added that unvaccinated children are at an eight times higher risk of getting the disease compared to those who have had the vaccine.
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