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Whooping cough cases rising in U.S. as vaccine weakens over time

COLUMBUS, Ohio—Whooping cough, a disease Americans figured they whipped with the modern medical miracle of childhood vaccinations, is soaring again throughout the nation in numbers not seen in decades.

When pediatric infectious disease specialist Dr. Dennis Cunningham of Children's Hospital here tells parents that their child has whooping cough, something he has been doing a lot lately, they often ask him: "They still have that around?"

Down to barely 1,000 cases in 1976, pertussis—the scientific name for whooping cough—steadily rose in 1980s and 1990s in America. Then it jumped, first to 9,771 in 2002 and then to 11,647 in 2003. Preliminary numbers for last year showed the case almost reached 19,000.

This year, even though it's not high season yet, whooping cough cases are nearly double last year's level. It's on a pace to pass 37,000 cases. In the first 12 weeks of 2005, there have been 3,445 whooping cough cases—more than in 1981 and 1982 combined.

Scientists believe that the disease is infecting adolescents whose childhood vaccinations are wearing off, so this spring federal health officials are expected to approve and then recommend a new booster shot for young teens.

"Pertussis is a substantial public health problem in the U.S.," said Dr. Karen Broder, a Centers for Disease Control and Prevention medical epidemiologist specializing in infectious childhood diseases.

It's hitting the heartland hardest. Kansas, Indiana, Wisconsin, Iowa, North Dakota and Ohio have all seen large numbers of whooping cough recently.

Whooping cough can be fatal to infants under 6 months and health officials worry the rise of pertussis around babies makes them more susceptible before they start to get shots at age 2 months. From 1979 to 2002, 128 people died from whooping cough, 117 of them were under 1 year old.

And most cases of whooping cough go undiagnosed.

"The amount of pertussis that is out there is underestimated by a very large extent by our ability to recognize and treat the disease," said CDC's childhood infectious disease chief Dr. Trudy Murphy.

Ohio has been hit the hardest of any state this year with 441 cases so far, more than the entire year of 2003. And Columbus' Franklin County has more whooping cough than any other county.

"It's nowhere near slowing down in the community," Cunningham said.

For awhile the lab at Children's Hospital in Columbus confirmed about 20 positive pertussis tests a day, and there was always an infant or two fighting for breath and life in the neonatal intensive care unit, Cunningham said.

The same week in March that Broder was lecturing public health officials at an immunization conference about the renewed dangers of whooping cough, her boss, CDC director Dr. Julie Gerberding, pronounced that the United States had essentially conquered German measles. Polio and measles have also been vanquished in America with vaccines.

"It's the only vaccine-preventable disease that's increased in the last 10 years," said Iowa state epidemiologist Dr. Patricia Quinlisk.

The major problem is that unlike other childhood diseases that have vaccines, whooping cough's shots seem to wear off, after about five years.

Young children get a series of immunizations that go until about 6 years old. But now public health officials realize that the immunity for whooping cough wanes, unlike the lifelong protection we get from polio or German measles shots. Even if you get whooping cough once, you can get it again, unlike other diseases.

For many years, doctors didn't realize that pertussis immunity weakened.

"People were so pleased and the success was so great (from the vaccine, which reduced the disease from hundreds of thousands of cases a year) that there was a lack of interest in pursuing these very difficult questions" about immunity waning, CDC's Murphy said.

One top expert in whooping cough, UCLA pediatrics professor Dr. James Cherry said waning immunity is one issue, but he also attributes the increase to a change in vaccines about 15 years ago. The old whooping cough vaccine was made from whole cells, but had problems with reactions, the new vaccine is made from parts of cells so they don't produce as severe a reaction, he said. However, he said the newer vaccines are slightly less effective.

CDC officials don't buy that explanation. They say the massive increase in whooping cough is primarily in adolescents who have gone at least five years since their shots, which is explained by waning immunity. Adults also are getting whooping cough, but it often goes undiagnosed.

Last month, a Food and Drug Administration advisory committee recommended the approval of two pertussis booster shots for teens, replacing a tetanus-diphtheria shot with a combo tetanus-diphtheria-pertussis vaccination.

Next month, the FDA is expected to approve the use of boosters and a month later the CDC's immunization advisory panel will then likely recommend it for teens. If it works after that, adults may get boosters years from now, officials say.


(c) 2005, Knight Ridder/Tribune Information Services.

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