Health

CDC links Calif. pertussis epidemic to less effective vaccine

Dr. Daniel Kahn holds the Tdap vaccine, which he administers to pregnant women in their third trimester.
Dr. Daniel Kahn holds the Tdap vaccine, which he administers to pregnant women in their third trimester.
Rebecca Plevin/KPCC

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In California, cases of pertussis have reached a nearly 70-year high in 2014, according to a new report from the Centers for Disease Control and Prevention. In the Morbidity and Mortality Weekly Report, the CDC warns that higher incidence of pertussis could become the "new normal," at least until there's a new vaccine available, or a more effective vaccine strategy.

During this year's epidemic, the state recorded close to 10,000 cases of pertussis, or whooping cough, through November 26. The rate of disease was highest among kids under 1 year, followed by 14 to 16-year-olds.

The report suggests this epidemic isn't linked to kids not getting the Tdap vaccination, which protects against pertussis, tetanus and diphtheria. In fact, most of the teens who got sick had been immunized, less than three years earlier.

Rather, the CDC says, the increase in cases of the disease is due to a less effective vaccine.

The acellular pertussis vaccine replaced the whole-cell vaccine in the 1990s. The new vaccine is less likely to cause a reaction, but it also confers immunity for a shorter amount of time, the report says.

This increase in disease would most endanger infants, who are at highest risk of severe illness of death from pertussis. So the CDC is urging women in their third trimester of pregnancy to get the Tdap shot. That way, they pass immunity onto their newborns, protecting them until they're old enough to get vaccinated.

But that strategy has been slow to take hold. The CDC cites two California studies from 2012 and 2013, which found that less than a quarter of mothers received the vaccination during pregnancy. Many more were vaccinated after delivery, but that doesn’t provide infants with direct protection.