Haemophilus influenzae type b carriage in Indigenous children and children attending childcare centers in the Northern Territory, Australia, spanning pre- and post-vaccine eras

BIGDATA: A Protocol to Create and Extend a 25-Year Clinical Trial and Observational Data Asset to Address Key Knowledge Gaps in Otitis Media and Hearing Loss in Australian Aboriginal and Non-Aboriginal Children

INTRODUCTION

Otitis media (OM) is a common childhood illness, often resolving without intervention and acute and long-term complications are rare. However, Australian Aboriginal and Torres Strait Islander infants and children experience a high burden of OM and are at high risk of complications (tympanic membrane perforation and chronic infections). Bacterial OM is commonly associated with Streptococcus pneumoniae, non-typeable Haemophilus influenzae, and Moraxella catarrhalis. BIGDATA is a data asset combining over 25 years of microbiology and OM surveillance research from the Ear Health Research Program at Menzies School of Health Research (Northern Territory, Australia), including 11 randomized controlled trials, four cohort studies, eight surveys in over 30 remote communities (including data from Western Australia), and five surveys of urban childcare centers including Aboriginal and Torres Strait Islander and non-Indigenous children. Outcome measures include clinical examinations (focusing on OM), antibiotic prescriptions, pneumococcal vaccination, modifiable risk factors such as smoking and household crowding, and nasopharyngeal and ear discharge microbiology including antimicrobial resistance testing.

METHODS AND ANALYSIS

The initial series of projects are planned to address the following key knowledge gaps: (i) otitis media prevalence and severity over pre pneumococcal conjugate vaccines (PCVs) and three eras of increasing PCV valency; (ii) impact of increasing valency PCVs on nasopharyngeal carriage dynamics of pneumococcal serotypes, and antimicrobial resistance; (iii) impact of increasing valency PCVs on nasopharyngeal carriage dynamics and antimicrobial resistance of other otopathogens; and (iv) serotype specific differences between children with acute OM and OM with effusion or without OM. These data will be utilized to identify research gaps, providing evidence-based prioritization for ongoing research.

ETHICS AND DISSEMINATION

Data asset creation and priority analyses were approved by the Human Research Ethics Committee of Northern Territory Department of Health and Menzies School of Health Research (EC00153, 18-3281), the Child and Adolescent Health Service Human Research Ethics Committee and Western Australian Aboriginal Health Ethics Committee. Dissemination will be through peer review publication and conference presentations.

Haemophilus influenzae type b disease in the era of conjugate vaccines: critical factors for successful eradication

INTRODUCTION

Prior to implementation of Haemophilus influenzae type b (Hib)-conjugate vaccination programs in the 1990s, Hib was the commonest cause of bacterial meningitis in children aged <5 years. While the burden of all Hib disease has significantly decreased in the post-vaccination era, Hib still accounted for >29,000 deaths worldwide in children aged <5 years in 2015.

AREAS COVERED

We reviewed literature data on the most widely used Hib vaccines and vaccination strategies which led to the global prevention and control of Hib disease and aim to highlight important factors for continued disease control and elimination in the future.

EXPERT COMMENTARY

More than 90% of countries worldwide have implemented Hib-conjugate vaccination in their national immunization programs. Vaccines containing Hib polyribosylribitol phosphate (PRP) conjugated with tetanus toxoid (Hib-TT) are the most commonly used. Neisseria meningitidis outer membrane protein complex of PRP (Hib-OMP) is also used. Although the kinetics of the immune response varies with Hib vaccine and schedule used, high control of Hib disease was observed in all settings/scenarios. Further improving global Hib vaccination coverage may result in disease elimination. Plain language summary What is the context? Haemophilus influenzae is causing a variety of diseases, from otitis media and sinusitis to invasive disease (e.g. meningitis and pneumonia). H. influenzae type b (Hib) was the most common cause of bacterial meningitis in children <5 years of age, and especially among <2-year-olds. Even with appropriate treatment, up to 40% of children with bacterial meningitis can suffer permanent disabilities and up to 5% will die. The development of vaccines to protect against Hib disease has started in the late 1970s and has culminated with the licensure of 4 Hib conjugate vaccines, of which 2 are currently widely used. What is new? In this review, we gathered evidence on the different Hib vaccines and vaccination strategies that have contributed to the global prevention and control of Hib disease. The review indicates: the incidence of Hib disease has decreased considerably due to the introduction of Hib vaccines in national immunization programs worldwide. However, Hib disease is not yet completely eradicated. the vaccines currently used offer protection against Hib over long periods of time. carriage of the pathogen by healthy individuals seem to be less frequent, but data are still needed to fully evaluate the impact of vaccination. other H. influenzae types are now more frequent. Why is this important? Despite the huge success of Hib vaccination, continuous surveillance is needed to anticipate potential re-emergences and devise the best strategies for prevention and control of disease. Hib vaccination should be considered in the few countries who have not yet implemented it, to decrease associated morbidity and mortality.

Australian vaccine preventable disease epidemiological review series: invasive Haemophilus influenzae type b disease, 2000-2017

Introduction

Invasive Haemophilus influenzae type b (Hib) disease is rare in Australia following vaccine introduction in 1993. Two deaths in vaccinated children in 2017, and the Hib booster dose moving from age 12 months to 18 months in 2018, prompted this review.

Methods

Hib Case Surveillance Scheme 2000-2017 data were used to calculate incidence, incidence rate ratios (IRR) and vaccine failure (VF) trends. We used denominators from the Australian Immunisation Register to calculate incidence in immunised and unimmunised children.

Results

All-age national invasive Hib disease incidence halved from 0.13 per 100,000 population in 2000 to 0.06 in 2017. Of 345 cases notified in 2000-2017, 153 were born post-2000, with 51 (33%) Aboriginal and Torres Strait Islander (Indigenous), and compared with non-Indigenous children IRR was 8.34 (95% CI: 5.83-11.79), with no evidence of decrease. Overall case fatality rate was 12.4% (19/153); 6 cases had underlying medical conditions. The overall incidence of invasive Hib disease was over 8 times higher (16.6 per 100,000) in children with no recorded doses than in children with ≥1 vaccine dose (1.9 per 100,000). VF criteria were met in 65/145 (45%) cases aged >8 weeks, of whom 7 (11%) were immunocompromised and 6 (9%) died, with no evidence of VF increase over time.

Conclusion

Overall, invasive Hib disease incidence declined by 55% from 2000 to 2017, but marked disparity persists between Indigenous and non-Indigenous children. Following moving the fourth dose from 12 to 18 months in 2018, monitoring of 3-dose VFs will be important, especially in Indigenous children.

Risk factors and mitigation of influenza among Indigenous children in Australia, Canada, United States, and New Zealand: a scoping review

AIM

This review considers prominent risk factors and mitigation strategies of influenza among Indigenous children.

METHODS

Seven electronic databases were searched from the period of 2004-2017 to locate articles discussing influenza among Indigenous children in the developed circumpolar nations of Australia, Canada, United States, and New Zealand. Articles selected for inclusion discussed influenza among Indigenous children as either individuals or as a part of a community. Ancestry searches of articles meeting the review criteria were also undertaken to discern seminal research in this topic area.

RESULTS

From the 39 primary research studies included, marked risk factors and mitigation strategies of influenza among Indigenous children were identified using inductive analysis. Notable risk factors included age under 2 years, cigarette smoke exposure, presence of a chronic illness, and crowded living conditions. Successful mitigation of influenza for Indigenous children included strategies to improve vaccine coverage, provision of health education, and policy change.

CONCLUSION

In the past, the impact of influenza upon Indigenous communities has been devastating for both children and their families. By utilizing existing public health infrastructure and collaborating with culturally unique Indigenous groups, preventive action for Indigenous children at significant risk of contracting influenza can be realized.

Mercury Exposure and Poor Nutritional Status Reduce Response to Six Expanded Program on Immunization Vaccines in Children: An Observational Cohort Study of Communities Affected by Gold Mining in the Peruvian Amazon

Background: Poor nutritional status combined with mercury exposure can generate adverse child health outcomes. Diet is a mediator of mercury exposure and evidence suggests that nutritional status modifies aspects of mercury toxicity. However, health impacts beyond the nervous system are poorly understood. This study evaluates antibody responses to six vaccines from the expanded program on immunization (EPI), including hepatitis B, Haemophilus influenzae type B, measles, pertussis, tetanus, and diphtheria in children with variable hair mercury and malnutrition indicators. Methods: An observational cohort study (n = 98) was conducted in native and non-native communities in Madre de Dios, Peru, a region with elevated mercury exposure from artisanal and small-scale gold mining. Adaptive immune responses in young (3–48 months) and older children (4–8 year olds) were evaluated by vaccine type (live attenuated, protein subunits, toxoids) to account for differences in response by antigen, and measured by total IgG concentration and antibody (IgG) concentrations of each EPI vaccine. Mercury was measured from hair samples and malnutrition determined using anthropometry and hemoglobin levels in blood. Generalized linear mixed models were used to evaluate associations with each antibody type. Results: Changes in child antibodies and protection levels were associated with malnutrition indicators, mercury exposure, and their interaction. Malnutrition was associated with decreased measles and diphtheria-specific IgG. A one-unit decrease in hemoglobin was associated with a 0.17 IU/mL (95% CI: 0.04–0.30) decline in measles-specific IgG in younger children and 2.56 (95% CI: 1.01–6.25) higher odds of being unprotected against diphtheria in older children. Associations between mercury exposure and immune responses were also dependent on child age. In younger children, one-unit increase in log₁₀ child hair mercury content was associated with 0.68 IU/mL (95% CI: 0.18–1.17) higher pertussis and 0.79 IU/mL (95% CI: 0.18–1.70) higher diphtheria-specific IgG levels. In older children, child hair mercury content exceeding 1.2 µg/g was associated with 73.7 higher odds (95% CI: 2.7–1984.3) of being a non-responder against measles and hair mercury content exceeding 2.0 µg/g with 0.32 IU/mL (95% CI: 0.10–0.69) lower measles-specific antibodies. Log₁₀ hair mercury significantly interacted with weight-for-height z-score, indicating a multiplicative effect of higher mercury and lower nutrition on measles response. Specifically, among older children with poor nutrition (WHZ = −1), log₁₀ measles antibody is reduced from 1.40 to 0.43 for low (<1.2 µg/g) vs. high mercury exposure, whereas for children with good nutritional status (WHZ = 1), log₁₀ measles antibody is minimally changed for low vs. high mercury exposure (0.72 vs. 0.81, respectively). Conclusions: Child immune response to EPI vaccines may be attenuated in regions with elevated mercury exposure risk and exacerbated by concurrent malnutrition.

Paediatric invasive Haemophilus influenzae in Queensland, Australia, 2002-2011: Young Indigenous children remain at highest risk

AIM

Haemophilus influenzae continues to cause invasive disease in children despite widespread Hib immunisation. The significance of non-B serotypes continues to be investigated, with evidence of increased invasive non-typeable H. influenzae (NTHi) world-wide. The aim of this study was to examine the current epidemiological and clinical features of invasive H. influenzae disease in children in Queensland, Australia.

METHODS

A retrospective review was performed of all cases of invasive H. influenzae disease in children <18 years of age in Queensland between January 2002 and December 2011. Cases were identified from pathology records and data requested from treating hospitals.

RESULTS

Laboratory data were obtained for 144 cases and clinical/demographic data for 123 cases. The majority (72%) of cases were children <5 years of age. Annual incidence rate for all children <5 years was 7.4/100 000, and for Aboriginal and Torres Strait Islander children <5 years was 10.2/100 000. Serotype was reported for 132 isolates, 69 NTHi and 63 encapsulated strains. The most common clinical diagnoses were pneumonia, meningitis and bacteraemia without clinical focus. Of the patients, 5 patients died, and 12 had significant morbidity at hospital discharge.

CONCLUSIONS

While rates of invasive H. influenzae disease have decreased dramatically following the introduction of Hib vaccination, H. influenzae remains a cause of significant morbidity and mortality, and Aboriginal and Torres Strait Islander children remain particularly vulnerable.

An innovative approach to improve ear, nose and throat surgical access for remote living Cape York Indigenous children

INTRODUCTION

On a background of high rates of severe otitis media (OM) with associated hearing loss, children from the Torres Strait and Cape York region requiring ear, nose and throat (ENT) surgery, faced waiting times exceeding three years. After numerous clinical safety incidents were raised, indicating a failure of the current system to deliver appropriate care, the governing Hospital and Health service opted to deliver surgical care through an alternate process. ENT surgeries were performed on 16 consented children from two remote locations via the private health care system, funded by a health provider partnership.

METHODS

We examined the collaboration processes alongside clinical findings from this ENT surgery. Collated patient data, included patient demographics, clinical and audiometry presentation features were reviewed and compared pre and post-operatively. Cost savings associated with the use of TeleHealth post-operatively were briefly examined.

RESULTS

Surgeries were successfully completed in all 16 children. The reported mean waitlist time for ENT surgery was 1.2 years. Pre-surgery pure-tone average hearing thresholds were reported at left: 30.9 dB, right: 38.2 dB. The majority of presentations were for bilateral OM with Effusion (69%). Post-surgical follow up indicated successful clinical outcomes in 80% of patients and successful hearing outcomes in 88% of patients. Mean difference pure-tone average hearing thresholds, left: 8.4 dB and right: 11.2 dB. Furthermore, the majority of patients reported improved hearing and breathing. The use of TeleHealth for post-operative review enabled a minimum cost saving of AUD$21,664 for these 16 children. Overall, a high level of staffing resources was required to successfully coordinate this intense surgical activity.

CONCLUSION

This innovative approach to a health system crisis enabled successful ENT surgical and hearing outcomes in 16 children, whose waitlisted time grossly exceeded state health recommendations. Using private health facilities funded by a health partnership, while unlikely to be a suitable model of care for routine service delivery; may be applied as an adjunct service model when blockages and delays lead to sub-standard service provision. This approach may be applicable to other health care facilities when facing extended elective surgery wait times in ENT or other specialty areas.

Impact of Haemophilus influenzae Type B Conjugate Vaccines on Nasopharyngeal Carriage in HIV-infected Children and Their Parents From West Bengal, India

BACKGROUND

In addition to reducing Haemophilus influenzae type b (Hib) disease in vaccinated individuals, the Hib conjugate vaccine (HibCV) has indirect effects; it reduces Hib disease in unvaccinated individuals by decreasing carriage. Human immunodeficiency virus (HIV)-infected children are at increased risk for Hib disease and live in families where multiple members may have HIV. The aim of this study is to look at the impact of 2 doses of the HibCV on nasopharyngeal carriage of Hib in HIV-infected Indian children (2-15 years) and the indirect impact on carriage in their parents.

METHODS

This prospective cohort study was conducted in HIV-infected and HIV-uninfected families. Nasopharyngeal swabs were collected from children and parents before and after vaccination. HIV-infected children 2-15 years of age got two doses of HibCV and were followed up for 20 months. Uninfected children 2-5 years of age got 1 dose of HibCV as catch-up.

RESULTS

123 HIV-infected and 44 HIV-uninfected children participated. Baseline colonization in HIV-infected children was 13.8% and dropped to 1.8% (P = 0.002) at 20 months. Baseline carriage in HIV-uninfected children was 4.5% and dropped to 2.3% after vaccination (P = 0.3). HIV-infected parents had 12.3 times increased risk of Hib carriage if their child was colonized (P = 0.04) and had 9.3 times increased risk if their child had persistent colonization postvaccine (P = 0.05). No parent of HIV-uninfected children had Hib colonization at any point. Pneumococcal colonization was associated with increased Hib colonization.

CONCLUSION

Making the HibCV available to HIV-infected children could interrupt Hib carriage in high-risk families.

Vaccination for the control of childhood bacterial pneumonia - Haemophilus influenzae type b and pneumococcal vaccines

Pneumonia in childhood is endemic in large parts of the world and in particular, in developing countries, as well as in many indigenous communities within developed nations. Haemophilus influenzae type b and Streptococcus pneumoniae conjugate vaccines are currently available against the leading bacterial causes of pneumonia. The use of the vaccines in both industrialised and developing countries have shown a dramatic reduction in the burden of pneumonia and invasive disease in children. However, the greatest threat facing pneumococcal conjugate vaccine effectiveness is serotype replacement. The current vaccines provide serotype-specific, antibody-mediated protection against only a few of the 90+ capsule serotypes. Therefore, there has been a focus in recent years to rapidly advance technologies that will result in broader disease coverage and more affordable vaccines that can be used in developing countries. The next generation of pneumococcal vaccines have advanced to clinical trials.

Trends in the epidemiology of invasive Haemophilus influenzae disease in Queensland, Australia from 2000 to 2013: what is the impact of an increase in invasive non-typable H. influenzae (NTHi)?

Following the introduction of vaccination against Haemophilus influenzae type b (Hib), cases of invasive encapsulated Hib disease have decreased markedly. This study aimed to examine subsequent epidemiological trends in invasive H. influenzae disease in Queensland, Australia and in particular, assess the clinical impact and public health implications of invasive non-typable H. influenzae (NTHi) strains. A multicentre retrospective study was conducted from July 2000 to June 2013. Databases of major laboratories in Queensland including Queensland Forensic and Scientific Services (jurisdictional referral laboratory for isolate typing) were examined to identify cases. Demographic, infection site, Indigenous status, serotype, and mortality data were collected. In total, 737 invasive isolates were identified, of which 586 (79·5%) were serotyped. Hib, NTHi and encapsulated non-b strains, respectively, constituted 12·1%, 69·1% and 18·8% of isolates. The predominant encapsulated non-b strains were f (45·5%) and a (27·3%) serotypes. Of isolates causing meningitis, 48·9% were NTHi, 14·9% Hib, 14·9% Hie, 10·6% Hif, 6·4% Hia and 4·3% were untyped. During the study period, there was an increase in the incidence of invasive NTHi disease (P = 0·007) with seasonal peaks in winter and spring (P 0·001) and Hib (P = 0·039) than non-Indigenous patients. In Queensland, invasive H. influenzae disease is now predominantly encountered in adults and most commonly caused by NTHi strains with demonstrated pathogenicity extending to otherwise young or immunocompetent individuals. Routine public health notification of these strains is recommended and recent available immunization options should be considered.

A review of invasive Haemophilus influenzae disease in the Indigenous populations of North America

Historically, the highest incidence rates of invasive Haemophilus influenzae disease in the world were found in North American and Australian Indigenous children. Although immunization against H. influenzae type b (Hib) led to a marked decrease in invasive Hib disease in countries where it was implemented, this disease has not been eliminated and its rates in Indigenous communities remain higher than in the general North American population. In this literature review, we examined the epidemiology of invasive H. influenzae disease in the pre-Hib vaccine era, effect of carriage on disease epidemiology, immune response to H. influenzae infection and Hib vaccination in Indigenous and Caucasian children, and the changing epidemiology after Hib conjugate vaccine has been in use for more than two decades in North America. We also explored reasons behind the continued high rates of invasive H. influenzae disease in Indigenous populations in North America. H. influenzae type a (Hia) has emerged as a significant cause of severe disease in North American Indigenous communities. More research is needed to define the genotypic diversity of Hia and the disease burden that it causes in order to determine if a Hia vaccine is required to protect the vulnerable populations.

Delivering vaccines for the prevention of pneumonia - programmatic and financial issues

Pneumonia is the leading cause of morbidity and mortality in children younger than 5 years. Vaccines are available against the main bacterial pathogens Haemophilus influenzae type b and Streptococcus pneumoniae. There are also vaccines against measles and pertussis; diseases that can predispose a child to pneumonia. Partners such as the Global Alliance for Vaccines and Immunisation (GAVI), the Hib Initiative, the Accelerated Development and Introduction Plan for pneumococcal vaccines and the Measles Initiative, have accelerated the introduction of vaccines into developing countries. Whilst significant improvements in vaccine coverage have occurred globally over the past decade, there still remains an urgent need to scale-up key pneumonia protection and treatment interventions as identified in the Global Action Plan for the Prevention and Control of Pneumonia (GAPP). There is promise that global immunisation will continue to improve child survival. However, there are several challenges to vaccine implementation that must first be addressed, including: a lack of access to under-served and marginalised populations; inadequate planning and management; a lack of political commitment; weak monitoring and surveillance programmes and assured sustainable finance and supply of quality vaccines. There is an urgent need to increase global awareness of the devastation that pneumonia brings to the worlds poorest communities.

Broad conditions favor the evolution of phase-variable loci

Simple sequence repeat (SSR) tracts produce stochastic on-off switching, or phase variation, in the expression of a panoply of surface molecules in many bacterial commensals and pathogens. A change to the number of repeats in a tract may alter the phase of the translational reading frame, which toggles the on-off state of the switch. Here, we construct an in silico SSR locus with mutational dynamics calibrated to those of the Haemophilus influenzae mod locus. We simulate its evolution in a regimen of two alternating environments, simultaneously varying the selection coefficient, s, and the epoch length, T. Some recent work in a simpler (two-locus) model suggested that stochastic switching in a regimen of two alternating environments may be evolutionarily favored only if the selection coefficients in the two environments are nearly equal (“symmetric”) or selection is very strong. This finding was puzzling, as it greatly restricted the conditions under which stochastic switching might evolve. Instead, we find agreement with other recent theoretical work, observing selective utility for stochastic switching if the product sT is large enough for the favored state to nearly fix in both environments. Symmetry is required neither in s nor in sT. Because we simulate finite populations and use a detailed model of the SSR locus, we are also able to examine the impact of population size and of several SSR locus parameters. Our results indicate that conditions favoring evolution and maintenance of SSR loci in bacteria are quite broad.

Bacteria experience frequent changes of environment during the infection cycle. One means to rapidly adapt is stochastic switching: a bacterial lineage will stochastically produce a variety of genotypes, so that some descendants will survive if the environment changes. Stochastic switching mediated by simple sequence repeat (SSR) loci is widespread among bacterial commensals and pathogens and influences critical interactions with host surfaces or immune effectors, thereby affecting host persistence, transmission, and virulence. Here, we use the most detailed in silico model of an SSR locus to date, with its phase variation calibrated to match the mod locus of Haemophilus influenzae. The type III restriction-modification system encoded by mod participates in the regulation of multiple other genes; thus, SSR-mediated phase variation of mod has far-reaching cis-regulatory effects. This coupling of phase-variable switching to complex phenotypic effects has been described as the “phasevarion” and is central to understanding the infection cycle of bacterial commensals and pathogens.

The continuing role of Haemophilus influenzae type b carriage surveillance as a mechanism for early detection of invasive disease activity

Prior to the introduction of Haemophilus influenzae type b (Hib) conjugate vaccines, Hib was the leading cause of bacterial meningitis in children under five years of age worldwide. In countries that have adopted Hib vaccination schedules, invasive disease has reduced markedly. Oro-naso pharyngeal carriage is recognized as the most significant source of infection. Hib carriage is significantly associated with poverty, such as overcrowding, poor ventilation in houses, lack of running water, and high smoking rates. Additionally, many Indigenous minority groups report high rates of Hib carriage. A resurgence of Hib disease among Alaskan children in the 1990s, lead to a change in approach to eliminate Hib disease and carriage in high-risk populations. This new approach identifies strategies for eliminating Hib disease focusing on the reservoirs of colonization within families and communities. Monitoring Hib carriage continues to offer an early warning system, whereby intervention could prevent invasive disease resurgence.

Impact of vaccination against Haemophilus influenzae type b with and without a booster dose on meningitis in four South American countries

To inform World Health Organization recommendations regarding use of Haemophilus influenzae type b (Hib) vaccines in national immunization programs, a multi-country evaluation of trends in Hib meningitis incidence and prevalence of nasopharyngeal Hib carriage was conducted in four South American countries using either a primary, three-dose immunization schedule without a booster dose or with a booster dose in the second year of life. Surveillance data suggest that high coverage of Hib conjugate vaccine sustained low incidence of Hib meningitis and low prevalence of Hib carriage whether or not a booster dose was used.

Haemophilus influenzae type b infection, vaccination, and H. influenzae carriage in children in Minnesota, 2008-2009

An increase in invasive Haemophilus influenzae type b (Hib) cases occurred in Minnesota in 2008 after the recommended deferral of the 12-15 months Hib vaccine boosters during a US vaccine shortage. Five invasive Hib cases (one death) occurred in children; four had incomplete Hib vaccination (three refused/delayed); one was immunodeficient. Subsequently, we evaluated Hib carriage and vaccination. From 18 clinics near Hib cases, children (aged 4 weeks-60 months) were surveyed for pharyngeal Hib carriage. Records were compared for Hib, diphtheria-tetanus-acellular pertussis (DTaP), and pneumococcal (PCV-7) vaccination. Parents completed questionnaires on carriage risk factors and vaccination beliefs. In 1631 children (February-March 2009), no Hib carriage was detected; Hib vaccination was less likely to be completed than DTaP and PCV-7. Non-type b H. influenzae, detected in 245 (15%) children, was associated with: male sex, age 24-60 months, daycare attendance >15 h/week, a household smoker, and Asian/Pacific Islander race/ethnicity. In 2009, invasive Hib disease occurred in two children caused by the same strain that circulated in 2008. Hib remains a risk for vulnerable/unvaccinated children, although Hib carriage is not widespread in young children.