Pregnant women can help protect their newborns from whooping cough by getting a Tdap vaccine during the third trimester of pregnancy.

The U.S. Centers for Disease Control and Prevention tracked cases of infant whooping cough between Jan. 1, 2000, and Dec. 31, 2019.

The researchers found a link between reduced rates of whooping cough in newborns under 2 months of age and Tdap (tetanus, diphtheria, pertussis) vaccination during pregnancy.

Whooping cough, or pertussis, is highly contagious and can be serious for infants who are too young to be vaccinated. The CDC recommends babies get their first Tdap shot at 2 months of age.

"Getting Tdap during pregnancy offers infants the best protection before they are old enough to receive their whooping cough vaccines," Dr. José Romero, director of CDC's National Center for Immunization and Respiratory Diseases, said in a CDC news release. "This protection is critical because those first few months are when infants are most likely to have serious complications, be hospitalized or die if they get whooping cough."

The researchers had not looked at U.S. population level trends in infant whooping cough cases since this maternal vaccination strategy began in 2011. The CDC recommends all women get Tdap vaccines between their 27th and 36th week of each pregnancy.

Newborn whooping cough rates decreased significantly since vaccination of pregnant women began, according to the CDC. Maternal Tdap vaccination prevents more than three-quarters of cases of whooping cough in infants under 2 months of age.

Tdap vaccination during pregnancy dropped off during the COVID-19 pandemic, and the CDC and its partners are working to increase rates.

The CDC said that all people in close contact with infants should be up to date with their whooping cough vaccines.

"Everyone who is pregnant should feel confident in knowing that the Tdap vaccine is safe and effective," said Dr. Linda Eckert, the American College of Obstetricians and Gynecologists' liaison to CDC's Advisory Committee on Immunization Practices. "Knowing that Tdap vaccination during pregnancy protects 9 in 10 babies from being hospitalized with whooping cough, I strongly recommend this vaccine to all my pregnant patients for their peace of mind and for their family's health and well-being."