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Vaccinating for pertussis during pregnancy protects baby, study says

Dr. Daniel Kahn holds the Tdap vaccine, which he administers to pregnant women in their third trimester.
Rebecca Plevin/KPCC
The CDC's Advisory Committee on Immunization Practices recommends all pregnant women get the Tdap shot, which protects against pertussis.

A large-scale study of tens of thousands of births appears to validate the federal government's recommendation that pregnant women get vaccinated to protect their unborn babies from pertussis, also known as whooping cough. 

The study, published in the journal Pediatrics, finds that maternal Tdap vaccination during pregnancy is very effective in preventing whooping cough in infants before they get their first dose of pertussis vaccine and through their first year of life. The Tdap vaccine protects against tetanus, diphtheria and pertussis.

The study examined nearly 150,000 births at Kaiser Permanente Northern California from 2010 to 2015. Nearly 70,000 of the mothers had gotten the Tdap shot during pregnancy. The researchers find that for the babies born to the immunized mothers, the vaccine was more than 90 percent effective in preventing pertussis during the first two months of life and 69 percent effective during the first year of life.

The authors say their findings support the 2013 recommendationof the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices that all women should be vaccinated against pertussis during every pregnancy.

The thinking was that moms would pass pertussis antibodies on to their newborns, protecting them until they were old enough to get vaccinated. There was substantial research proving thesafety of this practice, but until the Pediatrics study, there was limited evidence of its effectiveness.

"I think this really provides a strong amount of support to improve vaccination rates for pregnant women around the country," says Dr. Nicola Klein, director of Kaiser Permanente's Vaccine Study Center in Oakland.

Klein says some scientists have worried that maternal vaccination could interfere with the effectiveness of the DTaP vaccine, which protects children against diphtheria, tetanus and pertussis. Kids get five doses of this immunization beginning at 2 months of age.

The study finds the opposite effect: After their first, second and third DTaP shots, kids whose mothers received the Tdap vaccine were better protected.

"We found that the Tdap vaccine seemed to add to the protection that the infants get from their own vaccines," Klein says.

An Oct. 2015 study by California's Department of Public health found that vaccinating pregnant women against pertussis provides greater protection to the small percentage of their infants who contract the disease.

Of the sick infants whose mothers did not get the vaccination, three out of four were hospitalized, according to the study. Less than half of those whose mothers did get the Tdap ended up in the hospital.