Effectiveness of two pertussis vaccines in preterm Danish children.

Reduced immunogenicity in preterm children has been observed for pertussis vaccines. How immunogenicity relates to clinical protection is not well-established for pertussis, and the corresponding reduction, if any, in post-licensure vaccination effectiveness among preterm children has not been determined. We conducted a nationwide cohort study of 879,424 Danish children including 1553 cases of pertussis hospitalisation. The effectiveness of pertussis vaccination, both whole-cell and acellular, was evaluated in preterm and full-term children. The effectiveness of a completed primary series of pertussis vaccination, whole-cell or acellular, was similar in preterm and full-term children.