Eradication of Haemophilus influenzae type b disease in southern California. Kaiser-UCLA Vaccine Study Group
C. M. Vadheim, D. P. Greenberg, E. Eriksen, L. Hemenway, N. Bendana, L. Mascola and J. I. Ward
UCLA Center for Vaccine Research, Research and Education Institute, Harbor-UCLA Medical Center, Torrance.
OBJECTIVE: To assess the effects of Haemophilus influenzae vaccination of
infants. RESEARCH DESIGN: We evaluated H influenzae type b (Hib) disease
rates in Los Angeles County, California (population, 9 million; 1983
through 1992), and in the Southern California Kaiser Health Plan (2.5
million enrollees; 1988 through 1992) during the past decade. Cases were
obtained through active and passive disease surveillance in the two
populations. The following vaccines were used during the study period (1983
through 1992): (1) Hib polysaccharide vaccine (polyribosyl ribitol
phosphate) (used from 1985 through 1987 for children 24 through 60 months
of age); (2) Hib polysaccharide-diphtheria toxoid conjugate, Hib
polysaccharide CRM197 mutant diphtheria toxoid conjugate vaccine, and Hib
polysaccharide outer-membrane protein of group B meningococcus conjugate
vaccine in older children (1988 through 1990; ages 15 through 60 months);
and (3) Hib polysaccharide CRM197 mutant diphtheria toxoid conjugate
vaccine and Hib polysaccharide outer-membrane protein of group B
meningococcus conjugate vaccine used in infants (1991 through 1992).
MEASUREMENTS AND RESULTS: Between 1983 and 1988, the Hib disease incidence
in Los Angeles County was unchanged (32.7 to 42.5/100,000 person-years in
children younger than 5 years). In 1989 through 1990, before Hib conjugate
licensure for infant use, Hib disease rates in all age groups declined.
After licensure of Hib vaccines for infants in 1990, there was a further
fivefold decrease in infants. More dramatic decreases occurred in the
better-immunized Kaiser Health Plan children aged 0 through 60 months (53
cases in 1989, only two cases in 1992). CONCLUSIONS: The Hib disease has
been nearly eradicated in a fully immunized population (Kaiser Health
Plan), and significant reductions have also occurred in Los Angeles County.
