Background: Maternal antibodies, transported through the placenta during pregnancy, contribute to the protection of infants from infectious diseases during the first months of life. The aim of this study was to measure the concentration of antibodies against several vaccine-preventable diseases in paired maternal and cord blood serum samples in preterm and term infants and to assess placental transfer ratios and infant antibody concentrations against vaccine-preventable diseases.
Methods: Antibody concentrations specific against pertussis proteins (pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae), diphtheria and tetanus toxins, and antibody concentrations specific against polysaccharides from Haemophilus influenzae type b and Neisseria meningitidis serogroup C were measured in cord blood samples from preterm (<32 weeks and 1500 g) and term infants and maternal serum samples, using a fluorescent bead-based multiplex immunoassay.
Results: A total of 96 preterm and 42 term infants and their mothers were included in the study. Placental transfer ratios of antibodies against all vaccine antigens were significantly lower in preterm infants (medians varied from 0.26 to 0.86) compared with term infants (medians, 0.74-1.89; all antibodies P < 0.05). Furthermore, polysaccharide-vaccine-specific antibodies showed lower transplacental transport ratios than protein-vaccine-specific antibodies. Maternal concentrations are the most important determinants of infant antibody concentrations against vaccine-preventable diseases.
Conclusions: Preterm infants benefit to a lesser extent from maternal antibodies against vaccine-preventable diseases than term infants, posing them at higher risk for infectious diseases in the first months of life.