Search

OBJECTIVES: The purpose of this study was to evaluate the effectiveness of Haemophilus influenzae type b (Hib) conjugate vaccines among children aged 2 to 18 months and to determine risk factors for invasive Hib disease during a period of declining incidence (1991-1994). METHODS: A prospective population-based case-control study was conducted in a multistate US population of 15.5 million. A laboratory-based active surveillance system was used for case detection. RESULTS: In a multivariate analysis, having a single-parent mother (odds ratio [OR] = 4.3, 95% confidence interval [CI] = 1.2, 14.8) and household crowding (OR = 3.5, 95% CI = 1.03, 11.7) were risk factors for Hib disease independent of vaccination status. After adjustment for these risk factors, the protective efficacy of 2 or more Hib vaccine doses was 86% (95% CI = 16%, 98%). Among undervaccinated subjects, living with a smoker (P = .02) and several indicators of lower socioeconomic status were risk factors for Hib disease. CONCLUSIONS: Hib disease still occurs at low levels in the United States, predominantly in socioeconomically disadvantaged populations. Low immunization coverage may facilitate continuing transmission of Hib. Special efforts to achieve complete and timely immunization in disadvantaged populations are needed.

To identify characteristics of day care facilities associated with H. influenzae disease, we compared 92 licensed facilities in which a case of H. influenzae disease had occurred with randomly selected facilities at which no cases occurred. Matched univariate analysis showed that personnel at facilities where H. influenzae disease occurred were more likely than those at control facilities to use towels or handkerchiefs to wipe children's noses, admit children who were not toilet trained or had diarrhea ("liberal fecal policy"), had a narrower age range, were more likely than control facilities to be for-profit and less likely to use volunteers. In a multivariate model that adjusted for age range, profit status and liberal fecal policy, towel or handkerchief use (OR 5.5, 95% CI: 1.1, 30) was the only variable independently associated with case facilities. This is the first association of a specific day care practice with H. influenzae disease.

Outbreaks and sporadic cases of meningococcal disease among college students have prompted consideration of a policy of routine vaccination for this group. Purchase and administration of the vaccine for routine vaccination would cost $56 million per year. Savings in medical care and indirect costs would not equal this amount unless the annual rate of disease among students is at least 6.5/100,000. The actual rate among students is unknown; however, surveillance data suggest it could not be more than 1.3/100,000. At rates near this estimate, the net cost of the program would be approximately $45 million annually. More cost-effective prevention strategies might be yielded by further studies to identify students at substantial risk of meningococcal disease, or by the development of a conjugate serogroup C vaccine that could be administered during infancy.