Safety and immunogenicity of an acellular pertussis vaccine in premature infants

Objectives. To evaluate the safety and immunogenicity of a two-component ac ellular pertussis vaccine in preterm infants. Study Design. Fifty preterm infants (25-35 weeks of gestation; mean, 30.8 w eeks) and 50 term infants as a control group received a two-component acell ular pertussis vaccine irrespective of their biological age and actual weig ht. Adverse reactions were registered by parents on a diary card and review ed on each visit. Antibodies against pertussis toroid (PT) and filamentous hemagglutinin (FHA) were determined with an enzyme-linked immunosorbent ass ay before the first and after the third vaccination. Results. The infants of both groups showed an increase in geometric mean ti ters (GMT) against PT and FHA after vaccination (3 doses). There was a sign ificant difference of antibody concentration between the preterm and the co ntrol group. The GMT for PT antibody of the preterm infants was 64.16 U/L, and for the term infants it was 98.96 U/L. The GMT for FHA was 50.92 U/L in preterm versus 86.02 U/L in the control group. Efficacy of the immunizatio n (more than a fourfold increase of antibody concentration in each infant) was 93.5% in the preterm group with respect to PT and 82.6% with respect to FHA. The incidence of adverse reactions was low and comparable in both stu dy groups. Conclusion. Immunization with an acellular pertussis vaccine is safe for pr eterm infants. The immune response is significantly lower compared with a c ontrol group of term infants, but efficacy is high.