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Vaccine’s long-term potency in doubt

Tue., Sept. 20, 2011

Pertussis shot’s effect may fade in three years

ATLANTA – The whooping cough vaccine given to babies and toddlers loses much of its effectiveness after just three years – a lot faster than doctors believed – and that could help explain a recent series of outbreaks in the U.S. among children who were fully vaccinated, a study suggests.

The study is small and preliminary, and its authors said the results need to be confirmed through more research. Nevertheless, the findings are likely to stir debate over whether children should get a booster shot earlier than now recommended.

“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, chief of infectious disease at the Kaiser Permanente Medical Center in San Rafael, Calif. Witt presented his findings Monday at the American Society for Microbiology conference in Chicago.

The study was done in California, where whooping cough vaccinations are a hot-button issue. The state had a huge spike in whooping cough cases last year, during which more than 9,100 people fell ill and 10 babies died. California schools have turned away thousands of middle and high school students this fall who haven’t gotten their booster shot.

Dozens of Kootenai County children were sickened with whooping cough last year and state health officials blamed the region’s poor vaccination rates.

Whooping cough cases rose in Washington to 608 according to state statistics, but the rate of infected children was lower than that of Idaho.

Government health officials recommend that children get vaccinated against whooping cough in five doses, with the first shot at age 2 months and the final one between 4 and 6 years. Then youngsters are supposed to get a booster shot around 11 or 12. That means a gap of five to eight years.

Witt’s study looked at roughly 15,000 children in Marin County, Calif., including 132 who got whooping cough last year. He found that youngsters who had gone three years or more since the last of their five original shots were as much as 20 times more likely to become infected than children who had been more recently vaccinated. The largest number of cases was in children 8 to 12 years old.

Whooping cough, or pertussis, is a highly contagious bacterial disease that in rare cases can be fatal. It leads to severe coughing that causes children to make a distinctive whooping sound as they gasp for breath.

California health officials told doctors last year that they could give the booster to kids as young as 7 in an effort to stifle the outbreak. Federal health officials said that they are still studying the issue and that it is too soon to make that a standard practice.

At the Centers for Disease Control and Prevention, which makes recommendations on childhood shots, officials acknowledged that the vaccine’s protection declines, but they said the agency’s own studies show the drop-off is not as pronounced as Witt’s research found.

CDC officials stressed that the vaccination is still much better than nothing – it reduces how sick a child becomes. Also, the nation no longer sees thousands of whooping cough deaths each year, as it did before there was a vaccine.

The shots “are still our best protection against pertussis, and they still protect well against fatal disease,” said Dr. Tom Clark, who leads the CDC’s epidemiology team focused on vaccine-preventable diseases.


 

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