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The highest pertussis antitussive concentrations were associated with immunization at the beginning of the third trimester, especially week 27 to 30 gestation.
Immunization of the mother during the third trimester with tetanus, diphtheria, and pertussis acellular vaccine (Tdap) was associated with higher neonatal concentrations of pertussis toxin antibodies compared to no immunization, according to data published in JAMA.
The Tdap vaccine is recommended in the United States during weeks 27 to 36 of pregnancy to prevent subsequent pertussis in infants. This prospective, observational, newborn cohort of Houston, Texas was undertaken between December 2013 and March 2014 to determine the optimal gestation age for immunization to maximize neonatal antibody concentrations.
A total of 626 pregnant women were included in the study and 312 received the Tdap vaccine at an average gestation of 31.2 weeks (range, 27.3-36.4). The remaining 314 women were not immunized. In the vaccine group, the mean geometric mean concentration of pertussis toxin antibodies in the neonatal cord was 47.3 IU / ml (95% CI, 42.1-53.2). In the unexposed group, the mean geometric mean concentration of pertussis toxin antibodies in the neonatal cord was 12.9 IU / ml (95% CI, 11.7-14.3), resulting in an average geometric concentration of 3.6 95% CI, 3.1-4.2; P <.001). Antibody concentrations of 15 IU / ml or greater were found to be more exposed than unexposed newborns, respectively 86% versus 37% (49% [95% CI, 42%-55%]). The same was true for geometric mean concentrations of 30 IU / ml or more (72% vs. 17%, the difference being 55% [95% CI, 49%-61%]) and 40 IU / ml or greater (59% versus 12%, difference, 47% [95% CI, 41%-54%]). The statistical significance has been demonstrated by P values <.001 for each analysis. Geometric mean concentrations were highest when the vaccine was administered during weeks 27 to 30, after which they decreased, reaching a peak at week 30 with a geometric mean concentration of 57.3 IU / ml (95% CI, 44 , 0 to 74.6).
As a result of the observational design of the study, the causal interpretations of the data are not possible, the investigators note. In addition, the study was conducted in a single center and was exploratory in nature without any formal calculation of power, so more extensive studies are needed to verify the results. Finally, serum preimmunization and post-stimulation samples were not collected, no woman was immunized during the second trimester of pregnancy, and the low number was immunized at late pregnancy.
Although more studies are needed, the researchers concluded that the study demonstrated "immunization with Tdap vaccine during week 27 to 36 pregnancy, as recommended [Centers for Disease Control and Prevention] to prevent life-threatening pertussis in young infants compared to no immunization was associated with significantly higher concentrations of pertussis toxin antibodies in neonates at birth. Investigators concluded with the statement that the highest antibody concentrations were associated with immunization at the beginning of the third trimester, especially in the weeks 27-30.
Reference
Healy CM, Rench MA, Swaim LS et al. The association between Tdap immunization in the third trimester and the neonatal pertussis antibody concentration. JAMA. 2018; 320: 1464-1470.
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