Children whose mothers received the tetanus, diphtheria, and pertussis (Tdap) vaccine during pregnancy exhibited a notably reduced immune response to their own vaccinations in early childhood. Nevertheless, booster vaccinations administered at age 4 normalized their immunity levels, according to a recent observational cohort study.
The study involved children receiving their primary diphtheria, tetanus, and acellular pertussis (DTaP) vaccinations at 3, 5, and 12 months of age. It was observed that by age 3, children whose mothers had the Tdap vaccine had geometric mean concentrations (GMC) of anti-pertussis toxin immunoglobulin G (anti-PT IgG) at 2.44 IU/mL, compared to 5.76 IU/mL in children of unvaccinated mothers (P=0.002). This significant difference persisted at age 4.
However, after receiving the DTaP booster at age 4, the immune levels in the children of vaccinated mothers were comparable to those of children of unvaccinated mothers (247 vs 270 IU/mL), as reported by Dr. Lauri Ivaska and colleagues from the University of Turku in Finland in the Journal of Infectious Diseases.
Dr. Ivaska and colleagues emphasized that maternal Tdap vaccination is a safe and effective strategy for protecting infants against pertussis, which remains a key reason for its administration during pregnancy. They noted that although maternally derived antibodies may affect antibody dynamics into childhood, the booster vaccination response seems to remain intact.
This study extends findings from the Finnish MIFI trial, which analyzed the dampening effect that maternal Tdap vaccination might have on infants’ responses to their primary DTaP shots.
In the United States, both the CDC and the American College of Obstetricians and Gynecologists recommend maternal Tdap vaccinations to offer newborns protection during the vulnerable period until they begin their primary DTaP vaccination at age 2 months. Infants younger than 3 months are at a heightened risk of severe consequences from pertussis infections, with approximately 1 in 100 infected infants succumbing to the illness.
The findings reinforce the recommendation for all pregnant women to receive the Tdap vaccine, as noted by Dr. Lori Handy, associate director of the Vaccine Education Center at the Children’s Hospital of Philadelphia.
Dr. Handy pointed out that a significant finding of this study is that infants born to mothers who were vaccinated during pregnancy displayed robust levels of antibodies at birth and at 3 months of age.
The study revealed that children born to Tdap-vaccinated mothers had significantly higher cord-blood anti-PT IgG GMCs than those born to unvaccinated mothers (93.7 vs 18.4 IU/mL, P<0.001). Additionally, children of vaccinated mothers displayed significantly better anti-diphtheria toxin (DT) seroprotection rates than those born to unvaccinated mothers (100% vs 62%, P<0.001).
Between April 2023 and July 2025, the research team evaluated preschoolers’ responses to pertussis, diphtheria, and tetanus at ages 3, 4, and following their 4-year DTaP boosters. At 4 years of age, 30 children of vaccinated mothers and 15 children of unvaccinated mothers participated in a pre-booster assessment.
For the study, concentrations of anti-DT IgG of at least 0.1 IU/mL were deemed fully protective, while anti-PT IgG concentrations of at least 5 IU/mL were considered seropositive.
Both groups of children, regardless of maternal vaccination status, exhibited declines in pertussis seropositivity and diphtheria seroprotection rates by age 3. Pertussis seropositivity was significantly lower in children of vaccinated mothers compared to those of unvaccinated mothers (21% vs 62%, P=0.003). Although both groups experienced a decline in anti-DT seroprotection rates by age 3 (8% and 25%, respectively), the difference was not statistically significant.
After the age-4 booster, anti-DT IgG GMCs increased in both groups: to 1.21 IU/mL in children of vaccinated mothers and to 1.14 IU/mL in those of unvaccinated mothers.
The researchers proposed that switching to a pertussis-only vaccine during pregnancy may provide early pertussis protection without diminishing children’s later diphtheria response. However, this approach might not resolve the diminished response to primary pertussis vaccination. They also suggested the possibility of administering the preschool DTaP booster at a younger age.
Nonetheless, Dr. Handy cautioned that changes to the U.S. vaccination schedule might not be justified if no clinical differences were found between DTaP-vaccinated children whose mothers were Tdap-vaccinated and those whose mothers were unvaccinated. Such changes would require further investigation into population-level infection rates and associated risks.
The study’s limitations included a small sample size and the loss of some children during the four-year follow-up period.
Disclaimer: The information provided is for educational purposes only and is not intended as a substitute for professional medical advice. Always consult your healthcare provider for personal recommendations regarding vaccinations and health decisions.
Fuente: https://www.medpagetoday.com/pediatrics/vaccines/123156
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