Tetanus-diphtheria-acellular pertussis (Tdap) vaccine is recommended for all pregnant women in the US as the key medical intervention to protect newborn infants from pertussis (whooping cough). However, the safety of giving the Tdap vaccine to pregnant women has not been fully determined. According to a study published in Human Vaccines & Immunotherapeutics, the Tdap vaccine is safe for both mothers and infants.

A team of University of Texas researchers analyzed health outcomes of 1,759 births and compared cases in which the mother was immunized with the Tdap vaccine (n = 1,109) to those where the mother was not vaccinated with this vaccine (n = 650).

“We took advantage of electronic medical records to look at the health of a large number of women and their infants, many more than some previous studies. We also examined more health outcomes than previous studies and were able to thoroughly check women’s medical records,” says the lead author Dr Abbey B. Berenson of the Department of Obstetrics & Gynecology and Center for Interdisciplinary Research in Women’s Health at University of Texas Medical Branch.

There was no difference in the six maternal and seven infant health outcomes, with one exception: the vaccinated mothers were less likely to deliver by C-section, an observation unlikely to be directly connected to the vaccine.

“Our study adds to the growing body of evidence that the Tdap vaccine is safe for pregnant women and their unborn children,” says Dr Berenson. “It’s important for women to get the Tdap vaccine while they are pregnant to protect their infants from pertussis. Doctors can share the findings of our paper with their pregnant patients to let them know the vaccine is safe for them and their babies.”

Caused by the Gram-negative bacterium Bordetella pertussis, the disease is an important cause of infant death around the world. According to the US Centers for Disease Control and Prevention, 200,000 cases of pertussis had been reported annually in the US alone before the vaccine became available. Routine immunization led to >90% decrease in the developed world, but the risk remains significant, particularly for infants, as the disease takes the lives of ~200,000 infants annually.

“Babies less than three months old are especially vulnerable to the devastating outcomes from pertussis. They are most at risk of dying from the disease. And yet, newborns don’t receive their first dose of DTaP (the pediatric vaccine for pertussis and two other diseases) until they are two months old and aren’t fully protected until they are six months old. Therefore it is extremely important to protect newborns from pertussis in other ways. Maternal immunization is one way to help protect them because the antibodies that the mom generates in response to the vaccine can be passed to her unborn child. These maternal antibodies can provide short-term protection to newborns,” concludes Dr Berenson.