Whooping cough, one of those ancient scourges that infant vaccination was meant to wipe out, is making a dangerous comeback: It turns out the vaccine that babies get starts wearing off by adolescence.

With outbreaks striking teenagers and adults, the government soon will decide if it's time for booster shots against the cough so violent it can break a rib.

Last week, manufacturer GlaxoSmithKline sought Food and Drug Administration permission to sell a booster; competitor Aventis Pasteur isn't far behind.

While boosters are debated, however, don't lose sight of the real risk: Whooping cough (search) can kill newborns before they start getting their vaccinations. And while older patients usually recover, they can easily spread the disease, known medically as pertussis (search), to infants.

"Parents who have very young infants need to get them vaccinated as early as possible," advises Dr. Trudy Murphy of the Centers for Disease Control and Prevention (search) in Atlanta. Anyone who's coughing should "avoid contact with young infants on the chance this maybe is unrecognized pertussis."

Pertussis is a bacterial infection. Initial coldlike symptoms lead to fits of 15 to 20 coughs in a row that leave patients gasping for air — often, but not always, with a high-pitched "whoop."

The incidence of pertussis plummeted in industrialized nations after vaccination began in the 1940s. It now is on the rise again globally.

Why isn't clear, but it's thought to be at least partly due to waning immunity. Children get five doses of pertussis vaccine between ages 2 months and 6 years. The protection begins to drop five to 10 years after the last shot.

In the United States, a preliminary CDC count found more than 11,000 pertussis cases last year. That's up from 9,771 the previous year, and the most recorded in three decades.

"We know that's an underestimate," Murphy said.

Experts say there may be 10 times as many cases, even more. Studies suggest almost a quarter of people with coughs that last longer than two weeks have undiagnosed pertussis, says Dr. Kathryn Edwards of Vanderbilt University.

In fact, about a third of CDC-recorded cases are among adolescents, which even health professionals may not realize. So far this year, CDC has counted outbreaks, most involving teens, in 11 states, including a Chicago-area one that has involved more than 100 cases since March.

"I really thought it was a disease of the Depression," said Monika Burke, a Philadelphia nurse who was stunned when her 15-year-old daughter, Sophia, caught whooping cough in May.

A doctor first diagnosed a viral infection. But Sophia was having 30 or 40 coughing fits a day, occasionally so violent they'd trigger vomiting. So the doctor prescribed antibiotics and performed a blood test for pertussis. By the time test results came back a week later, her 12-year-old brother was sick, too.

Enter the booster debate. Proponents say booster shots for older ages could prevent misery and school and work absences, plus indirectly protect vulnerable infants: Since 1990, pertussis has risen 72 percent among babies younger than 4 months, the age when their vaccine protection begins to kick in.

Studies show that giving one-third of youngsters' pertussis vaccine doses to teens and adults can safely boost waning immunity. Already, boosters are offered in Canada, Germany, France and Australia.

Here, Glaxo last week asked the FDA to approve its Boostrix version for teens. The idea: People are supposed to get boosters against two other diseases, tetanus and diphtheria, every decade, including one for 11- to 18-year-olds. Boostrix simply adds a pertussis booster to the scheduled adolescent shot.

Competitor Aventis Pasteur wants to target adults, too. It is preparing to seek FDA approval to sell its Adacel pertussis-tetanus-diphtheria booster to ages 11 through 64.

Once FDA makes sales decisions, expected early next year, a CDC-appointed committee must recommend who should get whichever shots are sold. Adolescents likely will be the first candidates, noted Vanderbilt's Edwards. After all, they wouldn't require an extra doctor's visit or needle prick.

Less is known about adult pertussis risk. Still, new parents and infant caregivers and health workers are logical next choices "so we can cocoon babies," she said. "It's the babies that could die."