Impact of a regional Hib vaccination programme in Italy.

In the Veneto region of Italy, a coverage of 26% for Haemophilus influenzae type b (Hib) primary vaccination in 1-year-old children plus a 31-53% catch-up coverage in children 1-4 years of age resulted in a 91% reduction of Hib invasive disease in children <5 years of age. These data suggest that vaccination of older children can contribute substantially to herd immunity, even in settings where primary vaccination is low. Since a single Hib vaccine dose is efficacious in preventing Hib invasive disease in children over 1 year of age, and the costs of vaccination are reduced, catch-up should always be considered when introducing Hib vaccine in routine immunization programmes.