"The magnitude of the increase in California is concerning, and that's why we are trying to emphasize the importance of vaccination," Liang said.
Vaccination guidelines call for children to receive doses of pertussis vaccine at 2 months, 4 month, 6 months, between 15 and 18 months and then again at school age, between 4 to 6 years. Children should also receive a booster between the ages of 11 and 12.
Previous recommendations called for women to get vaccinated right before or right after pregnancy to protect infants. But in the wake of the epidemic, California public health officials are now advising pregnant women to get vaccinated.
Since 2005, the CDC has also recommended adolescents and adults up to age 64 receive a one-time booster shot because immunity from childhood pertussis immunization wanes over time, said Christina Chambers, an epidemiologist and a professor of pediatrics at the University of California, San Diego.
The shot itself, called Tdap, typically also includes a tetanus and diphtheria booster.
Yet few adolescents and adults are following expert recommendations, Liang said. A 2008 CDC study found about 40 percent of adolescents aged 11 and 12 had gotten the booster, while only 6 percent of adults had.
Though there little data explicitly looking at whether the vaccine is safe for pregnant women, there is no evidence that getting the vaccine can bring on the disease or carries any other risks. The pertussis vaccine is made up of an inactivated, or "killed," virus, Chambers explained.
"There is no data to suggest [that] giving the pertussis vaccine during pregnancy will cause harm," said Chambers, director of the California Teratogen Information Service (CTIS) Pregnancy Health Information Program, which provides counseling for pregnant women on
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