(HealthDay News) — Preliminary evidence shows that immunization with the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine is safe during pregnancy, according to a study published in the May 7 issue of the Journal of the American Medical Association, a theme issue on child health. This issue was released early to coincide with the annual meeting of the Pediatric Academic Societies, held from May 3–6 in Vancouver, Canada.

Flor M. Munoz, MD, from the Baylor College of Medicine in Houston, and colleagues randomized 48 pregnant women (aged 18–45 years) to receive either Tdap (33 patients) or placebo (15 patients) at 30–32 weeks of gestation, with crossover immunization postpartum.

The researchers observed no Tdap-associated serious adverse events in women or infants. After Tdap immunization, injection site reactions were reported in 26 pregnant and 12 postpartum women (P>0.99). Twelve pregnant women and 11 postpartum women reported systemic symptoms (P=0.03). Both infant groups showed similar growth and development. No pertussis occurred. In women who received Tdap during pregnancy, significantly higher concentrations of pertussis antibodies were measured at delivery, compared to those receiving vaccination postpartum (P<0.001). Similar results were seen in their infants at birth (P<0.001) and at age 2 months (P<0.001). Antibody responses between the two groups of infants did not differ following the fourth dose of the diphtheria and tetanus toxoids and acellular pertussis vaccine.

“Further research is needed to provide definitive evidence of the safety and efficacy of Tdap immunization during pregnancy,” the authors write.

Several authors disclosed financial ties to the pharmaceutical industry.

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