The first effective vaccine for whooping cough was developed in 1940. Before that, the respiratory infection killed thousands each year -- and it may be making a comeback.
Hundreds of cases are being reported in nine states. Washington State has declared an epidemic, with 1,484 cases. CBS News correspondent Dr. Jon Lapook has taken a look at what is behind the outbreak.
Heidi Bruch of Seattle did everything she was told during her pregnancy. Unfortunately, that didn't include getting a booster shot against whooping cough. She caught the disease and passed it to her two-week-old daughter, Caroline.
"My heart just sank. Oh my gosh" said Bruch. "I had inadvertently given my newborn a potentially fatal disease. It was a horrible feeling."
Caroline recovered after a month in the hospital, but it was touch-and-go. Dr. Wendy Sue Swanson is a pediatrician at the Everett Clinic in Mill Creek, Wash. Her county has seen 264 cases so far; that's more than the entire state had last year at this time.
"Newborns and infants in particular are at highest risk for complications," Swanson said. "They can have a serious, life-threatening pneumonia. They can have pauses, or cessation in their breathing, where they stop breathing."
Eighty-two percent of cases have been in children under age 18. All four fatalities in Washington this year were infants.
Children get their first three doses of whooping cough vaccine at two, four and six months. According to the Centers for Disease Control, 95 percent of kids in the U.S. get those first vaccinations. But immunity wears off over time.
The CDC said adults need one booster shot after age 18. But today only 8 percent of adults get that recommended booster.
Washington Secretary of Health Mary Selecky is urging people to get immunized.
"This is about taking care of yourself, your family, but also your community," said Selecky.
"As a parent, you don't want to go through this," said Bruch. "Having this booster available: It's a no-brainer. Go and get it."
Last year, the CDC began recommending that pregnant women be vaccinated against whooping cough for two reasons: To protect mothers like Heidi Bruch; and because protective antibodies pass to a child before birth, which helps newborns too young to be vaccinated themselves.