A case-control study of risk factors for Haemophilus influenzae type B disease in Navajo children.

Abstract

Abstract. To understand the potential risk factors and protective factors for invasive Haemophilus influenzae type b (Hib) disease, we conducted a case-control study among Navajo children less than two years of age resident on the Navajo Nation. We analyzed household interview data for 60 cases that occurred between August 1988 and February 1991, and for 116 controls matched by age, gender, and geographic location. The Hib vaccine recipients were excluded from the analyses. Conditional logistic regression models were fit to examine many variables relating to social and environmental conditions. Risk factors determined to be important were never breast fed (odds ratio [OR] ϭ 3.55, 95% confidence interval [CI] ϭ 1.52, 8.26), shared care with more than one child less than two years of age (OR ϭ 2.32, 95% CI ϭ 0.91, 5.96); wood heating (OR ϭ 2.14, 95% CI ϭ 0.91, 5.05); rodents in the home (OR ϭ 8.18, 95% CI ϭ 0.83, 80.7); and any livestock near the home (OR ϭ 2.18, 95% CI ϭ 0.94, 5.04).Before the widespread use of conjugate vaccines, incidence rates of invasive Haemophilus influenzae type b (Hib) disease among Navajo children were demonstrated to be much higher than in the general U.S. population. During the 1970s, the incidence of Hib meningitis for Navajo children less than five years of age was 152 per 100,000 child-years, 1 compared with 19-60 per 100,000 in various non-Native American communities. 2 The reasons for these elevated rates are not well understood, although environmental factors, genetic predisposition, and delayed maturation of immune functions all may be implicated.Many factors have been identified in population groups other than the Navajo as being associated with increased risk of Hib disease incidence. These include the use of shared child care facilities, 3-7 large family size or crowding, 5,6,8,9 low socioeconomic status, 8 and smoking. 8 Breast feeding has been shown to be protective. 3,5,6,9,10 In a case-control study of Navajo children, we investigated these and other factors that were unique to the environmental and cultural characteristics of this population, including heating fuels, husbandry practices, and arts and crafts activities.Although Hib disease has been virtually eliminated in this Navajo population, it is a leading cause of serious childhood illnesses in many countries where Hib vaccines are not routinely administered. 11,12 This case-control study, conducted in a predominantly rural and disadvantaged community just prior to licensure of Hib conjugate vaccines, has relevance to many less industrialized populations. MATERIALS AND METHODSSurveillance for Hib disease. From July 1988 through July 1990, active laboratory-based surveillance for Hib disease was carried out on the Navajo Nation in Arizona and New Mexico as part of a trial designed to evaluate the safety and efficacy of a Hib conjugate vaccine (Hib-OMPC: PedvaxHIB; Merck, Blue Bell, PA). 13 Further surveillance for Hib disease was conducted as part of a study to evaluate the effectiveness of implementation of a Hib va...

Association of Secondhand Smoke Exposure with Pediatric Invasive Bacterial Disease and Bacterial Carriage: A Systematic Review and Meta-analysis

“…The 12 case-control studies on SHS exposure and invasive Hib disease included a total of 1,228 cases and 3,076 controls (Table 1) [3],[36],[44]–[53]. The overall effect size was positive but nonsignificant (pooled OR 1.22, 95% CI 0.93–1.62; test of heterogeneity p =  0.011, I 2  = 55.0%) (Figure 2C).…”

“…In subgroup analysis, studies with laboratory-confirmed diagnosis had a similar effect size of 1.24 (95% CI 0.86–1.78), whereas adjusted studies yielded a lower and nonsignificant effect size (OR 1.10, 95% CI 0.80–1.51) [3],[36],[44],[46]–[53]. Studies on preschool children had a significant positive association (OR 1.46, 95% CI 1.19–1.81) (Table 2) [3],[36],[44]–[47],[49],[52],[53]. Studies before 1990, when Hib vaccine was not yet commonly available, had a stronger positive association (OR 1.49, 95% CI 1.16–1.93) than the overall analysis [3],[44]–[47].…”

Haemophilus influenzae type a as a cause of paediatric septic arthritis

“…In the Arctic, an augmented transmission rate of H. influenzae was reported to be associated with smoking in pregnancy, prematurity, lack of breastfeeding, shared care with more than one child younger than 2 years of age, adoption status, Inuit ethnicity, as well as with wood heating, rodents in the home, livestock near the home, overcrowding and rural residence (Banerji et al , 2009; Hennessy et al , 2008). In Navajo children, poor housing conditions, such as a lack of an in-home water service, were reported to increase H. influenzae type b infection rates (Wolff et al , 1999). Similar socio-economic factors underlying an increased susceptibility to invasive H. influenzae disease are commonly present in various indigenous populations (Tsang et al , 2014).…”

A review of invasiveHaemophilus influenzaedisease in the Indigenous populations of North America

“…Among young children, greater exposure to the pathogen due to poor housing conditions, such as overcrowding and lack of access to adequate volume of water in the home may cause high transmission rates of H. influenzae [71]. Several epidemiological studies have found an association of invasive Hib disease with indicators of low socioeconomic status (low income, single parents, low parental education levels, household crowding, indoor wood heating, rodents in the home), number of children in a family, shared childcare facilities, parental smoking and lack of breastfeeding in Navajo and Alaska Native children [22, 72]. High burden of chronic conditions, such as obesity, diabetes, chronic obstructive pulmonary disease, tuberculosis as well as a prevalence of smoking, alcohol and substance abuse that have been identified as important health issues in Canadian Indigenous populations [73] may have a negative effect on natural immunity against H. influenzae in the population and hence contribute to an enhanced circulation of the pathogen in Indigenous communities.…”