DO NOT FORGET IMMUNIZATIONS

July 22, 2010 — Six infants have died in California in what looks like the state's worst whooping cough epidemic in 50 years.

To date, the CDC says South Carolina is the only other state where whooping cough cases have exceeded the "epidemic threshold" -- a statistical measure that means there are significantly more cases than usual for the time of year.

After declaring an official epidemic of pertussis, the medical term for whooping cough, California health officials announced a broadened vaccination campaign for teens and adults of all ages. Anyone who comes into contact with babies is particularly urged to get the vaccine -- even pregnant women and the elderly.

"Teens and adults should be vaccinated, especially anyone who is going to have contact with infants who are too young for vaccinations," CDC epidemiologist Stacey Martin, MSc, tells WebMD. "Those California deaths were all in infants less than 3 months old. They don't have the benefit of vaccination yet, so we have to vaccinate around them."

Infants get three doses of the vaccine but are not fully protected until after they are 6 months old.

Neither the pertussis vaccine nor natural infection gives a person lifelong immunity to whooping cough. Outbreaks tend to occur in five-year cycles, suggesting that immunity wanes within that time.

Pertussis is one of the diseases covered by the three-way DTaP (diphtheria/tetanus/acellular pertussis) vaccine for children under age 7 years and by the three-way booster Tdap vaccine for older children, teens, and adults. There is no standalone pertussis vaccine.

Although a person needs a tetanus vaccination only once every 10 years, it's not a problem to get the Tdap vaccine at shorter intervals. Adults who get the tetanus and Tdap shots within two years may have more redness and soreness at the place the needle went in, but no significant safety issues.

Whooping Cough: A Serious Disease

Pertussis is a bacterial infection. It's named whooping cough for the "whooping" sound a person with the disease makes while trying to catch a breath between coughing fits.

The cough can be so severe that it causes broken blood vessels in the face, eyes, and even in the brain. But the main risk to small children is suffocation, said Dean Blumberg, MD, associate professor of pediatrics at the University of California, Davis, who has treated infants with whooping cough.

"Pertussis is a horrible disease at any age, but most severe in the youngest infants," Blumberg said at a Monday news teleconference. "The reason is their airways are so small. When they get pertussis they cough, cough, cough, and keep coughing. The air goes out but nothing comes in, so they suffocate."

The California vaccination effort may yet head off the epidemic. As of July 17, there were about 1,500 reported cases in the state. But time may be running out. July, August, and September tend to be peak months for whooping cough.

Vaccine Refusal Driving Whooping Cough Epidemic?

There's indirect evidence that people who refuse to vaccinate their children may be playing a role in the whooping cough epidemic, suggested Gilberto Chavez, MD, chief of the California Department of Health's infectious disease center.

Chavez noted that most whooping cough cases tend to occur in areas where the most parents exempt their kids from routine vaccination -- a choice that California state law permits the parents of school children.

"We have noticed that to some degree [the epidemic pattern] matches counties where there is a higher percent of kids not immunized because of personal-belief exemptions [to school-required vaccination]," he said at the news conference.

For example, Marin County north of San Francisco has a relatively high rate of vaccine refusal. Marin County has the highest number of whooping cough cases, Chavez said.

That fits with a 2008 study that matched whooping cough outbreaks in Michigan with geographic pockets of families that exempted their children from school immunization requirements.