Tdap Vaccination During Pregnancy Likely to Protect Newborns from Pertussis

Results of NIH-Funded Clinical Trial Support Maternal Vaccination
May 3, 2014
Vaccinating pregnant women with tetanus, diphtheria and acellular pertussis (Tdap) vaccine is safe, induces an immune response in women and is likely to protect their newborn infants against pertussis, according to the results of a recent clinical trial. The trial was conducted through a national network supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. It was led by Carol J. Baker, M.D., and Flor Munoz, M.D., of the Baylor College of Medicine, Houston.
In the United States, rates of pertussis-also known as whooping cough-have been increasing since the 1980s, with more than 24,000 cases reported in 2013. Newborns younger than 2 months old are too young to receive the Tdap vaccine and are at increased risk of complications and death if they contract pertussis. (Children aged 2 months to 7 years receive DTaP vaccine, administered as a series of injections, that protects against diphtheria, tetanus and pertussis. Adolescents and adults receive Tdap.) In this trial, researchers vaccinated 33 healthy pregnant women with a single dose of Tdap and 15 pregnant women with a placebo during the third trimester of pregnancy. The researchers then evaluated the safety of the vaccine; measured antibody responses induced in the pregnant women (during pregnancy, antibodies are passively transferred through the placenta to the fetus); and examined the infants' later immune system responses to the DTaP vaccine.
The researchers found Tdap to be safe for pregnant women, with no adverse pregnancy outcomes related to the vaccine. At delivery, Tdap-vaccinated pregnant women and their newborns had significantly higher concentrations of antibodies against pertussis than did both the women who received a placebo during pregnancy and their newborns. The elevated antibody levels in the Tdap-vaccinated newborns persisted for at least 2 months, increasing the likelihood that they were protected from pertussis during the time of greatest risk. While vaccinating pregnant women with Tdap did slightly reduce infants' pertussis antibody concentrations in response to the initial doses of DTaP vaccine, their antibody responses to the fourth dose of DTaP were robust. The trial results support the federal Advisory Committee on Immunization Practices' 2012 recommendation to vaccinate expectant mothers, the study authors write.
FM Munoz et al. Safety and immunogenicity of tetanus, diphtheria and acellular pertussis (Tdap) immunization during pregnancy in mothers and infants: A randomized clinical trial. Journal of the American Medical Association DOI: 10.1001/jama.2014.3633 (2014).
Linda Lambert, Ph.D., chief, Respiratory Diseases Branch, NIAID, is available to discuss the findings.
To schedule interviews, please contact Anne A. Oplinger, (301) 402-1663,
Additional information about the clinical trial can be found at using the identifier NCT00707148.
Content last reviewed on May 3, 2014