Pertussis Vaccination during Pregnancy could Substantially Reduce lnfant Deaths
Abstract & Commentary
By Philip R Fischer, MD, DTM&H, Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN. Dr. Fischer reports no financial relationships in this field of study.
SYNOPSIS: A mathematical model of three Tdap vaccination strategies supported the authors' conclusion that pregnancy vaccination is an economically efficient method to substantially reduce infant pertussis morbidity and mortality.
SOURCE: Terranella A, et al. Pregnancy dose Tdap and postpartum cocooning to prevent infant pertussis: a decision analysis. Pediatrics 2013;131:e1748-1756.
From 2001 to 2010, there were 27,995 reported cases of pertussis during the first year of life in the United States; 189 of these babies died. Children during the first two months of life account for most of these cases and deaths. When a source is identifiable, it is usually one of the parents. Various vaccine strategies have been proposed, including prenatal maternal vaccination and post-partum cocooning (providing vaccine to adults in close contact with the baby after birth). These strategies had been found to be cost-effective in Europe. Liang and colleagues sought to determine cost-effectiveness of pertussis vaccination in preventing infant pertussis in the United States.
A mathematical model was used based on the approximately four million babies born in the United States in 2009. The authors analyzed three vaccination strategies: 1) a pregnancy dose of Tdap vaccine, 2) a post-partum dose of Tdap, and 3) limited "cocoon" doses of Tdap to the parents and a grandparent.
Vaccine effectiveness was assumed to be 85% for the first six months post-vaccine. Transplacentally transferred maternal antibody was assumed to be 60% protective for two months in the infants.
Modeling suggested that without new intervention there would be 2041 infant pertussis cases per year with 1463 hospitalizations and 22 deaths. Post-partum maternal vaccination would avert 20% of infant cases, and third trimester maternal vaccination would prevent 33% of cases. Post-partum parental and grandparental vaccination would prevent 32% of cases. Intra-pregnancy vaccination was similarly predicted to prevent more hospitalizations and deaths and to save more quality-associated life years.
With these models, vaccination during pregnancy led to medical care cost savings of 37%, post-partum vaccination yielded 19% savings, and cocooned vaccinations prompted 32% savings.
The authors acknowledge that there are still questions of the safety of vaccination during pregnancy, the risk of blunting responses to subsequent infant pertussis vaccination, and implementation systems to reach pregnant women. While awaiting further studies, the authors claim that "pregnancy vaccination offers an economically efficient method to substantially reduce infant pertussis morbidity and mortality."
COMMENTARY
Despite widespread use of infant and adolescent pertussis vaccinations, babies are still dying of pertussis in the United States. The Centers for Disease Control and Prevention carefully considered various vaccination schemes, and this recent paper from Liang and colleagues explains some of those considerations. Based in part on these data, the CDC Advisory Committee on Immunization Practice (ACIP) recommended in February 2013 that all women receive Tdap during pregnancy, regardless of their previous vaccination history.1 This vaccine should be given between 27 and 36 weeks of gestation. In addition, all adolescents and adults who anticipate being in close contact with an infant should receive Tdap if they have not previously been vaccinated with Tdap.
Is Tdap safe enough during pregnancy? Byington and colleagues reviewed 162,448 pregnancies in a large health system in the western United States.2 Neither the 138 women who received Tdap vaccine during pregnancy (many during the first trimester as part of wound care) nor their babies had an increased incidence of adverse outcomes. Intra-partum use of Tdap seems safe.
National authorities making vaccine recommendations must balance the desire to prevent all disease and a desire to be wise with the use of limited health care resources. Societal pressure similarly pushes toward full protection with no risk. Wisdom is needed to balance these varied demands, and ACIP demonstrated wisdom with their recommendations earlier this year.
Some people might claim that ACIP simply wants to make people use all available vaccines. In their recent recommendations, as supported by the data in Liang's paper, the committee showed reasonable restraint in not obligating repeat Tdap for all contacts of infants. And, the new recommendations for intra-partum vaccination would clearly prevent illness, save lives, and reduce medical care costs.
The data are clear, and the time is now. All pregnant women should be vaccinated with Tdap between the 27th and 36th weeks of gestation, regardless of previous vaccination history.
References
- Sawyer M, et al. Updated Recommendations for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine (Tdap) in Pregnant Women — Advisory Committee on Immunization Practices (ACIP), 2012. MMWR 2013;62:131-135.
- Shakib JH, et al. Tetanus, Diphtheria, Acellular Pertussis Vaccine during Pregnancy: Pregnancy and Infant Health Outcomes. J Pediatr 2013;in press.
