The National Institutes of Health (NIH) funded the clinical trial, which vaccinated 33 pregnant women with a single dose of Tdap and 15 others with a placebo. The results found that both the vaccinated women and their babies had higher levels of antibodies against pertussis, commonly known as whooping cough.
The antibodies persisted in the newborns' bodies for at least two months, which the National Institute of Allergy and Infectious Diseases (NIAID) said is the time when babies are most likely to contract pertussis. Newborns at that age are generally too young to receive the Tdap vaccine.
The trial found no adverse effects on the babies of vaccinated mothers.
The study was conducted by a network of healthcare professionals supported by NIAID. It was led by doctors from the Baylor College of Medicine in Houston, Texas, who reported that their findings support a 2012 recommendation from the federal Advisory Committee on Immunization Practices to vaccinate expectant mothers.
Pertussis rates have increased in the United States since the 1980s. More than 24,000 cases were reported in 2013.