TEN YEARS OF HAEMOPHILUS INFLUENZAE TYPE B (HIB) IMMUNIZATION IN SWITZERLAND

Hp.E. Gnehm. H.P. Zimmermann

Children's Hospital Aarau and Federal Office of Public Health, Berne, Switzerland

OBJECTIVE: Ten years after the introduction of HIB immunization in Switzerland we want to know about the sustained effect of the vaccination program in respect to life threatening infections and to various age groups.

METHODS: Immunizations for infants and children are voluntary and covered by health insurance. 1990 PRP-D was the first HIB vaccine introduced, followed by PRP-OMP, PRP-OC and PRP-T recommended for routine immunizations. Surveillance of Hl-diseases is warranted by a mandatory reporting system of the Federal Office of Public Health for physicians and microbiological laboratories. Details concerning the patient, the illness, immunization status and bacteriological results are requested on additional report forms.

RESULTS: The overall incidence of invasive HIB in children (< 5 years) dropped by 95 % from 41 to 2/100'000, staying at this rate for the last 3 years. Meningitis cases decreased by 93 %, epiglottitis cases by 96 %. In the age group 0-2 years infection rates were reduced by 92 %, in those of 2 - 4 and 5 - 15 years by 96 and 83 % respectively. Of 320 children with invasive Hl-diseases occurring since 1991, 264 (83%) were not immunized, 29 (9 %) were incompletely immunized or infected by non type b strains or by strains not analyzed for serotype and 27 (8 %) received complete HIB immunization. Of the 27 HIB immunized but infected children 24 had received PRP-D vaccine, two the PRP-OMP and one PRP-T vaccine respectively before 1998. Up to the end of 1997 approximately 2 mio. doses of HIB-vaccine were administered to infants and young children. Comparing the share of 28% PRP-D to the total of HIB vaccines administered, vaccine failures in association with PRP-D (89%) are overrepresented.

CONCLUSIONS: The HIB-lmmunization program stays very effective since its start with various HIB-vaccine products. To obtain even better protection from HIB diseases highly immunogenic vaccines, early immunization and still higher vaccination rates are needed. These aims may be reached with the actually available combination vaccines for infants and children.