The 1996 pertussis epidemic in New Zealand: Vaccine effectiveness

Abstract

Aim. To assess if reduced vaccine effectiveness may have accounted for increased hospitalisations in the 1996 pertussis epidemic. Methods. Vaccine effectiveness was estimated by comparing vaccine coverage of the population (derived from a literature review) with that of cases (from notification data available from 1 June 1996) - the screening method. Only three doses of pertussis vaccine were in the immunisation schedule until 1996, so vaccine effectiveness was calculated for three or more doses. Results. Most likely estimates of vaccine effectiveness for Europeans were 88% (95% confidence interval 71 to 95%) for 5-to 14-month-olds, 80% for 15-month to 4-year-olds (66 to 88%) but lower for c..