Pertussis vaccine effectiveness in reducing clinical disease, transmissibility and proportion of cases with a positive culture after household exposure in Brazil.

In household outbreaks of pertussis, children <5 years of age who received at least 3 doses of vaccine had 12% less clinical disease; vaccinated cases were 63% less culture-confirmed and transmitted infection to 62% fewer contacts. Three doses of pertussis vaccine are likely to decrease circulation of Bordetella pertussis by reducing the proportion of bacteriologically positive cases and transmissibility.