Whooping cough protection fades in 3 years

ATLANTA -- The vaccine against whooping cough falters after only about three years, a preliminary study suggests, adding support to school rules requiring kids to get the vaccination periodically.

This year, California schools have turned away thousands of middle and high school students who haven't gotten the booster shot typically given at age 11 or 12. That state had a huge spike in whooping cough cases last year: More than 9,100 people became sick and 10 babies died after exposure from adults or older children.

The study of cases in Marin County, Calif., found the risk of getting the disease was as much as 20 times higher in kids three years or more after they finished receiving a recommended series of vaccinations. But kids vaccinated more recently were well-protected.

The findings may help explain why significant numbers of fully immunized children got whooping cough in the recent outbreaks.

"I was disturbed to find maybe we had a little more confidence in the vaccine than it might deserve," said the lead researcher, Dr. David Witt. He is chief of infectious disease at the Kaiser Permanente Medical Center in San Rafael.

Witt presented his findings yesterday at an infectious diseases medical conference in Chicago.

Whooping cough, also known as pertussis, is very contagious, though rarely fatal, except to babies too young to be vaccinated. The disease starts like a cold but leads to severe coughing that can last for weeks. It also is considered one of the hardest-to-control bacterial illnesses for which a common childhood vaccine is available. Health officials say the vaccine is effective in most people, and yet there are periodic outbreaks in places with high vaccination rates.

More than 80 percent of the children who developed whooping cough in Witt's study had been fully vaccinated.