Antibody persistence following primary and toddler booster vaccination of a hexavalent DTaP-IPV-HB-PRP∼T vaccine and immunogenicity of a school-age aP-containing booster vaccine in term and preterm infants born to women vaccinated with Tdap during pregnancy.

BACKGROUND

Previously, we reported strong immune responses in term and preterm infants following primary and toddler booster vaccination with a fully liquid DTaP-IPV-HB-PRP ∼ T hexavalent vaccine, irrespective of maternal Tdap vaccination status (NCT02511327). In this follow-up study in the same cohorts, we assessed antibody persistence after the primary series and toddler booster, and evaluated immunogenicity of a second, primary school-age booster of an aP-containing vaccine.

METHODS

Antibody persistence was evaluated at 3 and 5 years of age. Immunogenicity was assessed one month after a second aP-containing booster (Tetravac® [N = 78], Infanrix-IPV® [N = 14], Boostrix® [N = 2]) administered at 5-7 years of age through the Belgian healthcare system. All assays were validated and booster data were pooled across vaccines.

RESULTS

Of 232 infants in the baseline study, 128 children (71 term, 57 preterm) were included at 3 years, 106 children (62 term, 44 preterm) at 5 years, and 94 children (57 term, 37 preterm) received the school-age aP-containing booster vaccine. Antibody levels declined between 3 and 5 years of age in both groups and were generally higher in term children. Seroprotection rates remained high and comparable at 3 and 5 years of age, except for anti-HB, which was lower than the other antigens and declined over time. Following the booster, antibody levels increased markedly for all assessed antigens. One month post-booster, seroprotection rates reached 100% in both term and preterm groups for diphtheria, tetanus, and poliovirus type 1, and ≥ 96% for poliovirus types 2 and 3. Pertussis seroconversion and vaccine response rates were ≥ 93% in both groups.

CONCLUSIONS

These data support current maternal Tdap vaccination strategies and childhood booster vaccination policies in Belgium.