Protection provided by Haemophilus influenzae type b conjugate vaccines in Los Angeles County: a case-control study.
The objective was to assess the degree of disease control and to evaluate the protective efficacy of licensed Haemophilus influenzae type b (Hib) conjugate vaccines (HbOC, PRP-OMP, PRP-D) used routinely in children 2 to 35 months of age. We conducted a case-control study in Los Angeles County between January 1, 1991, and December 31, 1992, and a cohort analysis of Hib cases between 1983 and 1992. For the case-control study 105 cases of invasive Hib disease were identified and 767 geographically and age-matched controls were selected by random digit telephone dialing. Sixteen HbOC vaccine failures occurred > 14 days after a single dose of vaccine, 6 vaccine failures after 2 doses and 3 failures after 3 doses; 2 cases occurred 6 and 12 days, respectively, after an initial dose of HbOC. The protective efficacy of a single HbOC vaccine dose was 71.1% (95% confidence interval (CI), 37.5 to 87.2%). After 2 doses the efficacy was 88.8% (95% CI, 59.5 to 96.9%) and after 3 doses it was 94.4% (95% CI, 68.0% to 99.0%). Similar 95% CIs were seen for 1 and 2 doses of PRP-OMP vaccine. Adjustment of efficacy estimates for potential confounding variables did not significantly alter the results. Despite relatively low rates of immunization (20 to 60%) the rates of Hib disease decreased strikingly between 1990 and 1992 (from 24.2 to 4.4/100,000 children < 5 years of age). The HbOC conjugate vaccine, used predominantly but incompletely during this period, provided substantial protection against invasive Hib disease in children immunized between 2 and 35 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)
UCLA Center for Vaccine Research, Harbor-UCLA Medical Center, Torrance.
C M
CM
Vadheim
D P
DP
Greenberg
E
E
Eriksen
L
L
Hemenway
P
P
Christenson
B
B
Ward
L
L
Mascola
J I
JI
Ward
D016022:Case-Control Studies; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology / Q000517:prevention & control*; D018073:Haemophilus Vaccines; D006193:Haemophilus influenzae; D006801:Humans; D007223:Infant; D015141:Los Angeles / Q000453:epidemiology; D008297:Male; D012703:Serotyping
D018073:Haemophilus Vaccines