Pertussis serostatus among neonates born to Hispanic women.

The reasons for the higher pertussis incidence among Hispanic infants, compared with among infants of other ethnicities, are unknown. The geometric mean concentration of pertussis toxin-specific immunoglobulin G in serum samples from 220 Hispanic neonates was 8.45 EU/mL, as determined by enzyme-linked immunosorbent assay, and it was significantly lower if mothers were adolescents (4.63 EU/mL; P < or =.001). A lack of maternal immunity is one explanation for pertussis susceptibility in very young Hispanic infants.