This article is more than 5 years old. Information may no longer be current.
Maternal Tdap vaccine reduced infant pertussis risk by 91% in first 2 months
Children whose mothers received the tetanus-diphtheria-acellular pertussis vaccine during pregnancy exhibited a 91% reduced risk of pertussis within the first 2 months of life, according to new research published in Pediatrics.
Additionally, the researchers found that maternal Tdap vaccination did not interfere with infant diphtheria, tetanus and acellular pertussis (DTaP) vaccines but rather supplemented their protection.
“The strategy of immunizing pregnant women to boost maternal antibody transfer appears to be more effective for protecting young infants against pertussis than are attempts at ‘cocooning,’ in which mothers and other persons in close contact with newborns are vaccinated,” Nicola P. Klein, MD, PhD, codirector of the Kaiser Permanente Vaccine Study Center, and colleagues wrote. “Substantial evidence supports the safety of Tdap vaccination in pregnancy. However, there is limited evidence on its effectiveness, and only one study has estimated Tdap vaccine effectiveness in infants who have also received the DTaP vaccine.”
For researchers to evaluate and estimate the effectiveness of maternal Tdap vaccination during pregnancy before the first infant dose of DTaP at 2 months and 1 year, infants born at Kaiser Permanente Northern California between 2010 and 2015 (n = 148,981) were included in a retrospective cohort study. Each additional dose of DTaP given to a child was accounted for.
According to study results, the effectiveness of maternal Tdap vaccination at preventing pertussis was 91.4% during the first 2 months of life. Within the first year of life, maternal vaccination was 69.0% effective.
Before an infant’s DTaP vaccination, maternal vaccine efficacy was observed at 87.9%. Effectiveness of vaccination against pertussis reached 81.4% after one dose of DTaP was administered to the child, 6.4% after two doses and 65.9% after three doses.
“We should be cautious about the interpretation of how much additional protection infants are provided by maternal Tdap vaccination in addition to DTaP vaccination between the second and third doses, because the CI is wide,” Klein and colleagues wrote. “However, it is reassuring that at every level of DTaP vaccine exposure, children whose mothers received the Tdap vaccine are better protected.” — by Katherine Bortz
Disclosure: Drs. Baxter and Klein report potential conflicts of interest including the pertussis vaccines purchased by Kaiser Permanente Northern California, which are the focus of this study, were manufactured by GlaxoSmithKline and Sanofi Pasteur. The other authors have indicated they have no potential conflicts of interest.
Perspective
Back to Top
Resting critically on the assumption that aP vaccination protects the vaccinated against secondary transmission is the practice of ‘cocooning’ newborn infants, which entails vaccinating all close contacts (mother, father, siblings, grandparents) with a Tdap booster. If aP does not protect against transmission, this strategy will fail. And it has. Multiple studies, including the present, have shown little to no effectiveness of the cocooning strategy.
However, all is not lost with the aP vaccine. The current study is a nice contribution to the evidence base that receipt of a Tdap booster in the beginning of the third trimester — ideally between 27 and 36 weeks’ gestation — reduces the risk of pertussis infection in the critical 2 months before the infant’s first-round DTaP by nearly 90% and indeed for the entire first year of life (nearly 70% reduction), when pertussis infections are most severe. Similar reductions (>90%) in risk have been seen in the United Kingdom and in another study in the U.S.
Although it is becoming clear that a new vaccine for pertussis is desperately needed, it is heartening to see the effectiveness of maternal aP boosting in reducing pertussis infections in our infants at their most vulnerable. It further reiterates the importance of keeping vaccination levels high: if the only protection afforded by aP vaccination is direct, all immunocompetent children should be vaccinated because we cannot rely on the safety of herd immunity.
