Maternal immunization in the early third trimester (from 28 weeks’ gestation) may protect premature infants from pertussis, study results found.

This was the finding of an observational substudy of a larger multicenter, randomized, controlled vaccination trial of premature infants (the PUNS trial), which compared pertussis antibody concentrations before and after primary immunization in premature infants born to mothers who were or were not vaccinated with Repevax. Dr. Alison Kent of St George’s, University of London, and colleagues assessed the levels of the five vaccine antigens present in the maternal combination Repevax vaccine (pertussis toxoid, filamentous hemagglutinin, fimbriae types 2 and 3, diphtheria toxoid, tetanus toxoid, and inactivated poliovirus) in premature infants born to mothers who either received or did not receive Repevax from 28 weeks’ gestation. Antigen quantifications were conducted in these premature infants at approximately 2, 5, and 12 months of age.

Thirty-one (19%) of the 160 premature infants in the substudy were born to mothers who had been vaccinated. Two months after their premature birth, infants born to vaccinated mothers had significantly higher concentrations of all five measured antigens, compared with those born to unvaccinated mothers (all P values less than .001). Although fewer infants were sampled at 5 months of age, significantly higher concentrations of filamentous hemagglutinin and diphtheria toxoid were still found in those born to vaccinated mothers (both P = .003). Data collected at the 12-month assessment indicated that only tetanus antibody concentrations remained significantly higher in those born to vaccinated mothers (P = .015). A positive correlation between the number of days from maternal vaccination to delivery was found for all measured antigens, with the exception of fimbriae types 2 and 3.

“The emergency introduction of a maternal immunization program to control a national pertussis outbreak serendipitously provided an opportunity to assess antibody concentrations to maternal vaccine antigens in premature infants,” Dr. Kent and associates noted in Pediatrics (June 2016 doi: 10.1542/peds.2015-3854 ). This unexpected opportunity resulted in evidence supporting a protective effect against pertussis in the early lives of infants born prematurely to mothers immunized in their early third trimester.

Pfizer and the National Institute for Health Research Clinical Research Network funded the study. Professor Heath and Dr. Ladhani disclosed conducting studies on behalf of St George’s, University of London funded by vaccine manufacturers without receiving personal payments or travel support. The other authors reported no conflicts of interest.


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