Pertussis, also known as whooping cough, is a highly contagious bacterial infection of the respiratory tract that can obstruct breathing. It is especially dangerous to infants until they receive a 3-vaccine series called DTaP. The series usually begins at 2 months old and protects them against diptheria, tetanus, and pertussis. Several countries, including the United States, now recommended that pregnant have the Tdap vaccine to protect newborns from pertussis until they receive the DTaP series.
Researchers wanted to estimate the effectiveness of maternal pertussis vaccination during pregnancy for protecting newborns against pertussis. They looked at protection in the first 2 months of life before they start the vaccine series and in the first year of life while they are getting it. The study, published in Pediatrics, found that maternal Tdap vaccination during pregnancy is highly protective against infant pertussis, especially in the first 2 months of life.
About the Study
The cohort study assessed information gathered from 148,981 infants born at Kaiser Permanente Northern California from 2010 to 2015 during a whooping cough epidemic. The study had 2 overlapping follow up periods: birth to 2 months of age or birth to 1 year of age. Infants were followed until they had either had pertussis or reached 2 or 12 months of age. Out of the 148,981 infants 103 had pertussis during the study.
The study found that maternal Tdap during pregnancy reduced the risk of pertussis:
- 91.4% during the first 2 months of life when babies are not otherwise protected and can have more severe disease
- 69% during the entire first year of life after adjusting for the effects of DTaP vaccination
Furthermore, the study did not find evidence that the maternal Tdap and infant DTaP interfere with one another. Instead maternal Tdap added to the protection of infant DTaP. The maternal Tdap vaccine effectiveness was 87.9% before infants had any DTaP vaccine doses, 81.4% between doses 2 and 3, and 65.9% effective after all 3 doses.
How Does This Affect You?
Cohort studies are observational studies. These studies simply observe events as they unfold, but do not interfere or introduce factors that can affect the outcome. This is a large study, which generally increases the reliability of outcome. The study is also consistent with 2 earlier studies in the United Kingdom that also examined maternal Tdap in preventing pertussis. However, this study also confirmed that Tdap added to the protection of infant DTaP vaccinations.
The United States Centers for Disease Control and Prevention recommends that pregnant women receive a Tdap booster between 27 and 36 weeks of pregnancy. This study further supports this recommendation. If you are pregnant, talk to your obstetrician about the benefits of the Tdap vaccine.
- Reviewer: Michael Woods, MD, FAAP
- Review Date: 04/2017 -