A new CDC study published today in Clinical Infectious Diseases reported that vaccination with whooping cough vaccine, Tdap, during the third trimester of pregnancy prevented more than three out of four (78 percent) cases of whooping cough (also known as pertussis) in babies younger than two months. However, only 49 percent of pregnant women who delivered between fall 2015 and spring 2016 received the vaccine. CDC recommends women get Tdap during each pregnancy to provide critical short-term protection to babies when they are most at risk for this life-threatening illness.

The study used data from 2011 through 2014 on babies younger than two months from six states. It found that mothers whose babies had whooping cough were less likely to have received Tdap during pregnancy. The study reported that, in addition to being 78 percent effective at preventing whooping cough, Tdap vaccination during the third trimester was 90 percent effective at preventing serious cases of whooping cough that require hospitalization.

“Women have such a great opportunity to help protect their babies before they enter the world by getting Tdap vaccine while pregnant,” said Nancy Messonnier, M.D., director of CDC’s National Center for Immunization and Respiratory Diseases. “This study highlights how babies can benefit when their mothers get the vaccine and reinforces CDC’s recommendation for women to get Tdap vaccine in the third trimester of each pregnancy.”

 Young babies at highest risk

Whooping cough is a serious disease that can cause uncontrollable, violent coughing that often makes it hard to breathe. In this study, 65 percent of babies younger than two months who got whooping cough needed treatment in the hospital. Babies younger than one year are at the highest risk for severe complications or death. Typically, between five and 15 babies die from whooping cough each year in the United States. Most deaths are in those too young to be protected by getting their own whooping cough vaccines. Babies do not get vaccinated to start building their own protection against whooping cough until they are two months old.

Tdap vaccine history and recommendation

Before the introduction of whooping cough vaccines in the 1940s, more than 200,000 cases were reported per year in the United States. After vaccines became available, whooping cough cases declined dramatically to fewer than 10,000 cases reported by 1965. Beginning in the 1980s, whooping cough started making a comeback, though not to the levels seen before vaccines were available. Since 2010, there have been tens of thousands of whooping cough cases reported each year nationwide, with a peak of more than 48,000 cases reported in 2012. More than a third of all whooping cough hospitalizations and two thirds of all whooping cough deaths are in babies younger than two months. To date in 2017, more than 11,000 cases of whooping cough have been reported in the United States.

In 2012, CDC began recommending women get a whooping cough vaccine during each pregnancy. The American College of Obstetricians and Gynecologists and the American College of Nurse-Midwives, healthcare professionals who specialize in caring for pregnant women, support this recommendation, as do the American Academy of Pediatrics and the American Academy of Family Physicians. CDC recommends that doctors and midwives administer Tdap at 27 through 36 weeks of pregnancy, preferably in the earlier part of that period. This timing leads to the most transfer of protective antibodies from mothers to their babies.

Previous research

Today’s study adds to the growing body of research on Tdap vaccination during pregnancy that indicates it prevents whooping cough in babies who are too young to receive their own whooping cough vaccines. Three other studies from the United Kingdom and two from California also show much lower rates of whooping cough in babies whose mothers received Tdap during pregnancy. Another California study also found that babies with whooping cough whose mothers received Tdap during pregnancy were significantly less likely to need care in a hospital.

To learn more about CDC’s Tdap vaccine recommendation for pregnant women, visit CDC’s Pregnancy and Whooping Cough website.

For more information about whooping cough symptoms, prevention, and outbreaks, visit CDC’s Pertussis (Whooping Cough) website.