Baylor College of Medicine News

Pertussis vaccination during pregnancy could protect infants during period of highest vulnerability

Newborns whose mothers received the tetanus, diphtheria and acellular pertussis (Tdap) vaccine during pregnancy received immunity from their mothers at birth and in their first few months of life, and responded adequately to their own vaccinations, according to researchers at Baylor College of Medicine in a report that appears today in the Journal of the American Medical Association.

“Our findings support current recommendations from the Centers for Disease Control and Prevention that women should receive the Tdap vaccine during the third trimester of pregnancy to protect their newborns against pertussis,” said Dr. Flor Muñoz, associate professor of pediatrics – infectious diseases at Baylor and Texas Children’s Hospital and first author of the study.

Pertussis background

Pertussis, or whooping cough, is a highly contagious respiratory tract infection that can turn serious in infants. A rising number of pertussis cases have been reported in infants under 2 months of age who are too young to be vaccinated and can suffer complications and death from pertussis. Researchers have found that their mothers have very little pertussis antibodies from the vaccine that they themselves received during childhood.

Infants routinely receive five doses of the diphtheria, tetanus and acellular pertussis vaccine (DTaP) at 2, 4, 6 and 15 through 18 months and 4 through 6 years of age. The Tdap vaccine is given to those ages 11 and older, including adults, and it was recommended for all pregnant women in 2012.

Study focus

“Our study, which started in 2009, provides important information about how to prevent pertussis in babies who are at the greatest risk for complications and death from this disease because they are not getting protection from their mothers’ antibodies and are too young to have received their DTaP vaccine,” said Muñoz.

Researchers at Baylor and two other National Institutes of Health-funded Vaccine Treatment and Evaluation Unit sites, Duke University School of Medicine and Group Health Research Institute in Seattle, studied the previously-licensed adult vaccine for pertussis, Tdap, in 48 pregnant women, 33 of whom were vaccinated in the third trimester of pregnancy and 15 postpartum, and 32 non-pregnant women. 

Study results

The study found that:

The Tdap vaccine was safe in pregnant women. 

Pregnant women had adequate immune responses from the vaccine, similar to those of women who were not pregnant. 

At the time of delivery, women who were vaccinated during pregnancy had significantly higher concentrations of antibodies to pertussis compared to women who received the vaccine postpartum. 

Infants of mothers who received the vaccine during pregnancy had significantly higher concentrations of antibodies to pertussis at birth and in the first two months of life, likely providing protection during the period of highest vulnerability to pertussis and its complications.

Researchers continued to follow these babies during the first year of life and after receipt of routine vaccines for pertussis and measured their antibodies after the first three doses of DTaP and after their first booster and determined that even if their mother gave them antibodies from her Tdap vaccine during pregnancy, infants were able to respond to their own vaccine.

Implications

“Maternal immunization with Tdap is the most effective method currently available to protect babies against pertussis. However, infants need to receive their recommended vaccines starting at 2 months of age, even if the mother receives the vaccination during pregnancy,” said Munoz.

Dr. Carol J. Baker, professor of pediatrics at Baylor and Texas Children’s Hospital and senior investigator of the study, added that maternal immunization is not expected to be 100 percent effective in protecting babies.

“Infants still need to be protected before the first dose of DTaP so their care givers should also receive Tdap vaccine before the baby is born,” Baker said. 

Recommendations

The CDC recommends that pregnant women receive the Tdap vaccine during each pregnancy, preferably between 27 and 36 weeks of gestation, to protect newborns against pertussis.

Others who took part in the study include Nanette H. Bond, Dr. Maurizio Maccato, Dr. Phillip Pinell, Dr. Morven S. Edwards, Dr. and C. Mary Healy from Baylor; Dr. Hunter A. Hammill from a private practice in Houston; Dr. Geeta K. Swamy and Dr. Emmanuel B. Walter from Duke University School of Medicine; Dr. Lisa A. Jackson of Group Health Research Institute; Dr. Janet A. Englund of Seattle Children’s Research Institute; and Dr. Carey R. Petrie, Jennifer Ferreira and Johannes B. Goll of EMMES Corporation in Rockville, Md.

Funding for this study came from the National Institute of Allergy and Infectious Diseases, one of the National Institutes of Health.