http://pediatrics.medscape.com/viewarticle/423084?srcmp=ped-020502

 

Incidence of Pertussis Increasing Among Infants

 

 

ATLANTA (Reuters Health) Jan 31 - In the last 20 years, the number of pertussis cases has increased overall, especially among infants too young to receive three pertussis vaccine doses, according to the US Centers for Disease Control and Prevention (CDC).

The number of pertussis cases has remained stable among children old enough to be vaccinated, but the increase in cases in children younger than six months indicates that "a true increase in pertussis circulation has occurred," CDC researchers report in the February 1st issue of the CDC's Morbidity and Mortality Weekly Report.

From 1997 to 2000, over 7,000 pertussis cases among all age groups were reported each year, compared with about 2,000 cases per year in the early 1980s.

Among the 29,000 persons with pertussis from 1997 to 2000 for whom ages were known, 29% were aged less than 1 year, 12% were aged 1 to 4 four years, 10% were aged 5 to 9 years, 29% were aged 10 to 19 and 20% were twenty or older, the CDC reports.

Compared with surveillance data from 1994 to 1996, the new data indicate that the rate increased by 11% among infants, although it decreased by 8% among children aged 1 to 4 years and remained stable among children aged 5 to 9 years.

Additional data collected by the National Health Interview Survey (NHIS) in 1998 suggest that 73% of children aged 7 to 18 months were vaccinated with three or more doses of acellular pertussis (DTaP), diphtheria and tetanus toxoids (DTP), or diphtheria tetanus toxoids (DT) vaccines.

Vaccine effectiveness was estimated at 88% in children aged 7 to 18 months, with approximately two thirds of the vaccinations being DTaP and one third being DTP

"Prevention efforts should be directed at treatment of pertussis cases to prevent further spread of disease, use of antimicrobial prophylaxis in contacts of pertussis cases, and minimizing infant exposures to children and adults with cough illnesses," the CDC advises.

"Pertussis remains an endemic disease," Dr. Kris Bisgard, a medical epidemiologist with the CDC's National Immunization Program told Reuters Health. According to Dr. Bisgard, adolescents and adults likely play an important role in transmitting pertussis to very young infants.

"Infants less than 6 months of age are the most vulnerable to pertussis," she said. "However, data from this and other studies suggests that the DTaP is very effective in controlling pertussis among children 6 months to about 9 years of age."

MMWR 2002;51:73-76.

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