Vaccinating pregnant women against pertussis (whooping cough) )provides greater protection to the small percentage of their infants who contract the disease, according to a study released Friday by the California Department of Public Health.
In recent years, public health experts have been recommending that pregnant women get vaccinated against pertussis in the third trimester as a way to protect their infants from getting the disease when they are too young to be fully vaccinated.
A small percentage of babies will still contract pertussis, which can lead to hospitalization and in rare cases death, the Department said. But its study of 382 infants with pertussis found those whose mothers were vaccinated in the third trimester of pregnancy were much less likely to be hospitalized. Of those who were hospitalized, a far smaller percentage ended up in intensive care, none needed intubation, had seizures or died.
Of the sick infants whose mothers did not get the vaccination, known as Tdap (which protects against tetanus, diphtheria and pertussis), three out of four (77 percent) were hospitalized, according to the study. Less than half (44 percent) of those whose mothers did get the Tdap ended up in the hospital.
The babies whose mothers were unvaccinated experienced longer hospital stays (a median of six days versus three for the children of vaccinated moms) and were more likely to be admitted to intensive care (31 percent vs. 13 percent).
One in ten of the infants of unvaccinated moms required intubation, and six died. None of the children of vaccinated mothers needed intubation or died.
The children in the study were born from 2011 through August 2015.
Infants can get their first DTaP vaccine – which also protects against tetanus, diphtheria and pertussis – at around six weeks of age, but they are not considered fully protected until they have received at least three of the five recommended doses, usually by the time they are six months old. So the health department sees the vaccination of pregnant women -- recommended for the third trimester -- as another way to help protect newborns.
"Prior studies have demonstrated that prenatal Tdap vaccination reduces the risk of whooping cough among infants less than two months of age," said State Public Health Officer Dr. Karen Smith.
"However, this is the first study that CDPH is aware of that has evaluated the impact of Tdap vaccine during pregnancy on the outcomes of infants who do become infected with pertussis," she said. "This study provides more evidence that getting the Tdap vaccine is the best way for pregnant mothers to protect their babies from pertussis and its complications."
California is experiencing a "high" rate of pertussis this year - more than 4,200 as of this week, according to the public health department. Excluding the epidemic years of 2014 and 2010, the state has already had more cases reported in 2015 than in any year since the 1950s, it said.
Infants who contract pertussis do not have typical symptoms and may not appear to cough, according to the health department. "Instead, they may have difficulty breathing, their face may turn purple, and they may even stop breathing," it said.
Among children and adults, the disease starts with a cough and runny nose for a week or two, "followed by weeks to months of rapid coughing fits that sometimes end with a whooping sound and vomiting," according to the department, which adds that fever is rare.