Pertussis outbreak prompts questions about whether booster doses are needed
■ Nearly 18,000 cases and nine infant deaths were reported this year. An outbreak in Washington prompted state officials to declare an epidemic.
Waning pertussis immunity from the Tdap vaccine is helping drive the nationwide surge in cases of the bacterial disease this year, the Centers for Disease Control and Prevention said.
To help slow the spread of the illness, which has led to the deaths of nine infants since January, researchers are examining Tdap effectiveness and duration of protection among adolescents in California and Washington, said Anne Schuchat, MD, director of the CDC’s National Center for Immunization and Respiratory Diseases.
One question researchers are trying to answer is “whether you will need more booster doses during the adult years,” Dr. Schuchat said.
The CDC recommends that children receive five doses of DTaP (diphtheria, tetanus, acellular pertussis) vaccine between 2 months and age 6 and a booster of pertussis-containing vaccine (Tdap) between ages 11 and 12. The booster also is recommended for pregnant women and other adults who never received Tdap or can’t remember getting it.
Until new guidelines are issued, the CDC urges physicians to focus on administering Tdap to pregnant women and other adults who will have close contact with a baby. Data show that pertussis disproportionately affects infants, particularly those who are too young to be immunized.
“Our pertussis vaccines are not perfect,” Dr. Schuchat said. “They don’t provide protection for as long as we wish they would. But remember: Without vaccines, we know we would have hundreds of thousands of pertussis cases each year. Pertussis vaccine remains the single-most effective approach to prevent infection.”
There have been nearly 18,000 reported cases of the illness nationwide since January, according to July 19 figures from the CDC. That is the highest number of pertussis cases to be reported during that six-month period in the past five years.
“We may be on track for record-high pertussis rates this year,” Dr. Schuchat said.
A 2010 outbreak in California killed 10 infants and sent more than 800 adults and children to the hospital, making it the state’s worst pertussis epidemic in more than 50 years.
The disease is so prevalent in Washington, with 3,180 cases reported as of July 21, that the state’s Dept. of Health declared an epidemic in April. No deaths due to the illness have been documented in the state. During the same period in 2011, there were 230 reported pertussis cases in the state.
Wisconsin also has been hard hit by the disease, with 3,169 cases reported as of July 16, the CDC said (link).
Pertussis in Washington is highest among infants and children ages 10, 13 and 14, according to a study published in the July 20 issue of the CDC’s Morbidity and Mortality Weekly Report. The increased number of cases among teens is particularly concerning, because the pertussis booster is administered just a few years earlier, the CDC said.
Researchers examined all pertussis cases reported in Washington between Jan. 1 and June 16. They found that 76% of children 3 months to 10 years who contracted the disease were up to date with the childhood DTaP vaccine. Forty-three percent of children 11 and 12 received Tdap, as had 77% of teens 13 to 19, the study said (link).
“Vaccinated people who get whooping cough have milder symptoms [and] shorter illnesses and are less likely to spread the disease to others,” said Mary Selecky, secretary of health for the Washington State Dept. of Health. “Vaccination is still the best protection.”