Measurements of ion-electron energy-transfer cross section in high-energy-density plasmas.

We report on measurements of the ion-electron energy-transfer cross section utilizing low-velocity ion stopping in high-energy-density plasmas at the OMEGA laser facility. These measurements utilize a technique that leverages the close relationship between low-velocity ion stopping and ion-electron equilibration. Shock-driven implosions of capsules filled with D^{3}He gas doped with a trace amount of argon are used to generate densities and temperatures in ranges from 1×10^{23} to 2×10^{24} cm^{-3} and from 1.4 to 2.5 keV, respectively. The energy loss of 1-MeV DD tritons and 3.7-MeV D^{3}He alphas that have velocities lower than the average velocity of the thermal electrons is measured. The energy loss of these ions is used to determine the ion-electron energy-transfer cross section, which is found to be in excellent agreement with quantum-mechanical calculations in the first Born approximation. This result provides an experimental constraint on ion-electron energy transfer in high-energy-density plasmas, which impacts the modeling of alpha heating in inertial confinement fusion implosions, magnetic-field advection in stellar atmospheres, and energy balance in supernova shocks.

Association of Maternal Vitamin D Deficiency with Early Childhood Caries.

Alaska Native (AN) children experience one of the highest reported rates of severe early childhood caries (S-ECC). Serum vitamin D concentrations in AN childbearing women in the Yukon Kuskokwim Delta (YKD) region have decreased since the 1960s to currently low levels, related to a decrease in traditional marine diet. Recent studies suggest an association between prenatal vitamin D (25(OH)D) concentrations in mothers and S-ECC in their infants. We used independent t tests to analyze the influence of prenatal 25(OH)D levels in YKD AN mothers on S-ECC in their children using data collected in the Maternal Organics Monitoring Study (MOMS). Maternal 25(OH)D levels were assessed at prenatal visits and in cord blood. We queried electronic dental records to assess early childhood caries (ECC) status using highest decayed, missing, filled, primary teeth (dmft) scores at 12 to 59 mo of age. We examined prenatal and cord blood for 76 and 57 mother/infant pairs, respectively. Children 12 to 35 mo of age with "deficient" cord blood (25(OH)D <30 nmol/L) had a mean dmft score twice as high as children who were "nondeficient" at birth (9.3 vs. 4.7; P = 0.002). There was no significant difference in mean dmft scores for children aged 36 to 59 mo with deficient versus nondeficient cord blood 25(OH)D (10.9 vs. 8.7 P = 0.14). There was no significant difference in mean dmft scores for children aged 12 to 35 mo whose mothers had "sufficient" versus "insufficient" 25(OH)D during prenatal visits (9.0 vs. 7.4; P = 0.48). In this small sample, children with deficient vitamin D levels in cord blood had a dmft score at 12 to 35 mo 2-fold higher than children with nondeficient cord blood. Maternal 25(OH)D may influence the primary dentition, and improving vitamin D status in pregnant women might affect ECC rates in their infants.

Housing characteristics and indoor air quality in households of Alaska Native children with chronic lung conditions.

Alaska Native children experience high rates of respiratory infections and conditions. Household crowding, indoor smoke, lack of piped water, and poverty have been associated with respiratory infections. We describe the baseline household characteristics of children with severe or chronic lung disease participating in a 2012-2015 indoor air study. We monitored indoor PM2.5, CO2 , relative humidity %, temperature, and VOCs and interviewed caregivers about children's respiratory symptoms. We evaluated the association between reported children's respiratory symptoms and indoor air quality indicators using multiple logistic regression analysis. Compared with general US households, study households were more likely overcrowded 73% (62%-82%) vs 3.2% (3.1%-3.3%); had higher woodstove use as primary heat source 16% (9%-25%) vs 2.1% (2.0%-2.2%); and higher proportion of children in a household with a smoker 49% (38%-60%) vs 26.2% (25.5%-26.8%). Median PM2.5 was 33 µg/m3 . Median CO2 was 1401 ppm. VOCs were detectable in all homes. VOCs, smoker, primary wood heat, and PM2.5>25 µg/m3 were associated with higher risk for cough between colds; VOCs were associated with higher risk for wheeze between colds and asthma diagnosis. High indoor air pollutant levels were associated with respiratory symptoms in household children, likely related to overcrowding, poor ventilation, woodstove use, and tobacco smoke.

Use of d-3He proton spectroscopy as a diagnostic of shell rho r in capsule implosion experiments with approximately 0.2 NIF scale high temperature Hohlraums at Omega.

We present the calculations and preliminary results from experiments on the Omega laser facility using d-(3)He filled plastic capsule implosions in gold Hohlraums. These experiments aim to develop a technique to measure shell rho r and capsule unablated mass with proton spectroscopy and will be applied to future National Ignition Facility (NIF) experiments with ignition scale capsules. The Omega Hohlraums are 1900 microm length x 1200 microm diameter and have a 70% laser entrance hole. This is approximately a 0.2 NIF scale ignition Hohlraum and reaches temperatures of 265-275 eV similar to those during the peak of the NIF drive. These capsules can be used as a diagnostic of shell rho r, since the d-(3)He gas fill produces 14.7 MeV protons in the implosion, which escape through the shell and produce a proton spectrum that depends on the integrated rho r of the remaining shell mass. The neutron yield, proton yield, and spectra change with capsule shell thickness as the unablated mass or remaining capsule rho r changes. Proton stopping models are used to infer shell unablated mass and shell rho r from the proton spectra measured with different filter thicknesses. The experiment is well modeled with respect to Hohlraum energetics, neutron yields, and x-ray imploded core image size, but there are discrepancies between the observed and simulated proton spectra.

Pneumococcal vaccines for children and adults with bronchiectasis.

BACKGROUND: Bronchiectasis is increasingly recognized as a major cause of respiratory morbidity especially in developing countries. Even in affluent countries, bronchiectasis is increasingly seen in some community subsections (e.g. Aboriginal communities) and occurs as a comorbidity and disease modifier in respiratory diseases such as chronic obstructive pulmonary disease (COPD). Respiratory exacerbations in people with bronchiectasis is associated with reduced quality of life, accelerated pulmonary decline, hospitalisation and even death. Conjugate pneumococcal vaccine is part of the routine infant immunisation schedule in many countries. Current recommendations for additional pneumococcal vaccination include children and adults with chronic suppurative disease. OBJECTIVES: To evaluate the effectiveness of pneumococcal vaccine as routine management in children and adults with bronchiectasis in (a) reducing the severity and frequency of respiratory exacerbations and (b) pulmonary decline. SEARCH STRATEGY: The Cochrane Register of Controlled Trials (CENTRAL), the Cochrane Airways Group Specialised Register, MEDLINE and EMBASE databases were searched by the Cochrane Airways Group. Pharmaceutical manufacturers of pneumococcal vaccines were also contacted. The latest searches were performed in October 2006. SELECTION CRITERIA: All randomised controlled trials that utilised pneumococcal vaccine on children and adults with bronchiectasis. All types of pneumococcal vaccines were included. DATA COLLECTION AND ANALYSIS: Results of searches were reviewed against pre-determined criteria for inclusion. No eligible trials were identified and thus no data was available for analysis. One small non-randomised controlled trial in children was reported. MAIN RESULTS: No randomised controlled trials pertaining effectiveness of pneumococcal vaccine as routine management in children and adults with bronchiectasis were found. A benefit in elimination of Strep. pneumoniae in the sputum was found in a non-randomised trial in children but no clinical effect was described. AUTHORS' CONCLUSIONS: At present, there is a lack of reliable evidence to support or refute the routine use of pneumococcal vaccine as routine management in children and adults with bronchiectasis. Randomised controlled trials examining the efficacy of this intervention using various vaccine types in different age groups are needed. Until further evidence is available, it is recommended that health providers adhere to national guidelines.

The relationship of meteorological conditions to the epidemic activity of respiratory syncytial virus.

Our aim was to obtain knowledge of how meteorological conditions affect community epidemics of respiratory syncytial virus (RSV) infection. To this end we recorded year-round RSV activity in nine cities that differ markedly in geographic location and climate. We correlated local weather conditions with weekly or monthly RSV cases. We reviewed similar reports from other areas varying in climate. Weekly RSV activity was related to temperature in a bimodal fashion, with peaks of activity at temperatures above 24-30 degrees C and at 2-6 degrees C. RSV activity was also greatest at 45-65% relative humidity. RSV activity was inversely related to UVB radiance at three sites where this could be tested. At sites with persistently warm temperatures and high humidity, RSV activity was continuous throughout the year, peaking in summer and early autumn. In temperate climates, RSV activity was maximal during winter, correlating with lower temperatures. In areas where temperatures remained colder throughout the year, RSV activity again became nearly continuous. Community activity of RSV is substantial when both ambient temperatures and absolute humidity are very high, perhaps reflecting greater stability of RSV in aerosols. Transmission of RSV in cooler climates is inversely related to temperature possibly as a result of increased stability of the virus in secretions in the colder environment. UVB radiation may inactivate virus in the environment, or influence susceptibility to RSV by altering host resistance.

Crisis management during anaesthesia: vascular access problems.

BACKGROUND: In confronting an evolving crisis, the anaesthetist should consider the vascular catheter as a potential cause, abandoning assumptions that the device has been satisfactorily placed and is functioning correctly. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a specific sub-algorithm for vascular access problems, in the management of crises occurring in association with anaesthesia. METHODS: The potential performance of a structured approach was evaluated for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS). RESULTS: There were 128 incidents involving problems related to vascular access. The structured approach begins distally, checking the infusion device or fluid (12 incidents), moving proximally by way of the fluid giving line (10), the line deadspace (8), then the catheter/skin interface (65), and on to the peripheral vascular tree (3) and central venous space (23), and finally, the interface of the vascular access system and the attending staff (7). The approach was able to accommodate all the vascular access problems among the first 4000 incidents reported to AIMS. CONCLUSION: The approach has potential as an easily remembered and applied clinical tool to lead to early resolution of vascular access problems occurring during anaesthesia.

Crisis management during anaesthesia: water intoxication.

BACKGROUND: Irrigation of closed body spaces may lead to substantial perioperative fluid and electrolyte shifts. A syndrome occurring during transurethral resection of prostate (TURP), and a similar syndrome described in women undergoing transcervical endometrial ablation (TCEA) are both characterised by a spectrum of symptoms which may range from asymptomatic hyponatraemia to convulsions, coma, and death. Such potentially serious consequences require prompt recognition and appropriate management of this "water intoxication" syndrome. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a specific sub-algorithm for water intoxication, in the management of this syndrome occurring in association with anaesthesia. METHODS: The potential performance of this structured approach for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved. RESULTS: From the first 4000 incidents reported to AIMS, 10 reports of water intoxication were identified, two from endometrial ablations under general anaesthesia and eight from male urological procedures under spinal anaesthesia. The "core" crisis management algorithm detected a problem in seven cases; however, it was deficient in dealing with neurological presentations. Diagnosis of the cause of the incident would have required a specific water intoxication sub-algorithm in eight cases and a hypotension algorithm in a further two cases. Corrective strategies also required a specific sub-algorithm in eight cases, while the hypotension and cardiac arrest sub-algorithms were required in conjunction with the water intoxication sub-algorithm in the remaining two. CONCLUSION: This relatively uncommon problem is managed poorly using the "core" crisis management sub-algorithm and requires a simple specific sub-algorithm for water intoxication.

Modelling chorded prosthetic mitral valves using the immersed boundary method.

The Immersed Boundary (IB) Method is an efficient method of modelling fluid structure interactions. However, it has two main limitations: ease of use and ability to model static loading. In this paper, the method is developed, so that it can efficiently and easily model any multileaflet elastic structure. The structure may include chordae, which attach to the leaflets and continue through the leaflet surfaces. In addition, an external surface pressure may be applied to the leaflets, thus enabling the deformations that arise under steady loads to be solved. This method is validated for a model of the native mitral valve under systolic loading and for a prosthetic aortic valve under static loading. It is then applied to a new chorded prosthetic mitral valve, housed in a cylindrical tube, subject to a physiological periodic fluid flow. Results are compared with those obtained by using the commercial package ANSYS as well as with experimental measurements. Qualitative agreements are obtained. There are some discrepancies due to the current IB method being unable to model bending and shear behaviour. In particular, the fibre structures of the new prosthetic valve model developed using the IB method may be prone to crimping. Further development of the IB method is necessary to include bending effects. This will improve the accuracy of both the dynamic and static analysis.

Intra-axonal neurofilament compaction does not evoke local axonal swelling in all traumatically injured axons.

Traumatic axonal injury (TAI) contributes to morbidity and mortality following traumatic brain injury (TBI). Single-label immunocytochemical studies employing antibodies to neurofilament compaction (NFC), RM014, and antibodies to APP, a marker of impaired axonal transport (AxT), have shown that TAI involves both NFC and disruption of AxT. Although it may be hypothesized that both events occur within the same injured axon, this has not been confirmed. To determine the relationship between NFC and impaired AxT, dual-label immunofluorescence was employed. To compare and contrast specific changes associated with these two markers of TAI, single-label electron microscopy was also used. Rats were subjected to an impact acceleration injury (30 min-6 h survival), and their brains were prepared for dual-label immunofluorescence and single-label electron microscopy. APP and RM014 were consistently found in two distinct classes of TAI. One, which showed only RM014 immunoreactivity, was thin and elongate, was sometimes vacuolated, and revealed little progressive change over time. The second was distinguished by focal axonal swellings containing APP immunoreactivity alone in small-caliber axons or in combination with RM014 immunoreactivity in large-caliber axons. These swellings were localized to either nodal or internodal loci and underwent progressive swelling over time, ultimately leading to secondary axotomy. Ultrastructural examination of these two classes of TAI revealed NFC together with mitochondrial dilation without organelle pooling in the RM014 single-labeled axons. However, the APP single-labeled small-caliber axons and APP/RM014 dual-labeled large-caliber axons revealed a progressive accumulation of organelles associated with increased axonal swelling over time. In contrast to previous thought, it now appears that NFC may occur independent of impaired AxT in TAI. This finding underscores the complexity of TAI, suggesting the need for multiple immunocytochemical approaches to fully assess the overall axonal response to TBI.

The immunophilin ligand FK506 attenuates the axonal damage associated with rapid rewarming following posttraumatic hypothermia.

Our laboratory has shown that traumatically induced axonal injury (TAI) is significantly reduced by posttraumatic hypothermia followed by slow rewarming. Further, TAI can be exacerbated by rapid rewarming, and the damaging consequences of rapid rewarming can be reversed by cyclosporin A, which is believed to protect via blunting mitochondrial permeability transition (MPT). In this communication, we continue investigating the damaging consequences of rapid posthypothermic rewarming and the protective role of immunophilin ligands using another member of the immunophilin family, FK506, which does not affect MPT but rather inhibits calcineurin. Rats were subjected to impact-acceleration brain injury followed by the induction of hypothermia with subsequent rapid or slow posthypothermic rewarming. During rewarming, animals received either FK506 or its vehicle. Three hours postinjury, animals were prepared for the visualization of TAI via antibodies targeting impaired axoplasmic transport (APP) and/or overt neurofilament alteration (RMO-14). Rapid rewarming exacerbated TAI, which was attenuated by FK506. This protection was statistically significant for the APP-immunoreactive fibers but not for the RMO-14-positive fibers. Combined labeling, using one chromagen to visualize both axonal changes, suggested that these two immunoreactive profiles revealed two distinct pathologies not occurring along the same axon. Collectively, these studies confirmed previous observations identifying the adverse consequences of rapid rewarming while also showing the complexity of the pathobiology of TAI. Additionally, the demonstration that FK506 is protective suggests that calcineurin may be a major target for neuroprotection.

The immunophilin ligand FK506 attenuates axonal injury in an impact-acceleration model of traumatic brain injury.

The immunophilin ligand, cyclosporin A (CsA), is effective in reducing the axonal damage associated with traumatic brain injury (TBI). Based upon extensive ultrastructural and immunohistochemical studies, the neuroprotection afforded by CsA appeared to be mediated via mitochondrial protection, specifically, the prevention of mitochondrial swelling and inhibition of mitochondrial permeability transition (MPT). However, the potential that CsA could also be neuroprotective via the immunophilin-mediated inhibition of the protein phosphatase, calcineurin (CN) has not been directly assessed. To address this issue, the current study assessed the ability of FK506, another immunophilin ligand that inhibits CN with no effect on MPT, to attenuate axonal damage in a rat impact-acceleration model of TBI. Traumatic axonal injury (TAI), detected via an antibody against beta-amyloid precursor protein (APP), a specific marker of axonal injury, was significantly reduced at 24 hr postinjury in Sprague-Dawley rats receiving intravenous FK506 (2 mg/kg; n = 5) 30 min prior to injury compared to vehicle controls (n = 3). While not rejecting the established efficacy of CsA in providing neuroprotection via its targeting of MPT, this study does underscore the potential importance of CN in the progressive pathobiology of TAI, suggesting that CN may constitute another important therapeutic target.

Experience with the prevention of invasive Haemophilus influenzae type b disease by vaccination in Alaska: the impact of persistent oropharyngeal carriage.

OBJECTIVES: To report the epidemiology of invasive Haemophilus influenzae type b (Hib) disease in high-risk Alaska Native infants before and after universal infant Hib vaccination and evaluate an increase in invasive Hib disease in 1996 after changing Hib vaccine type. STUDY DESIGN: Statewide laboratory surveillance for invasive Hib disease has been conducted since 1980. Three cross-sectional Hib carriage studies were conducted in 1997 and 1998. RESULTS: The invasive Hib disease rate in Alaska Natives decreased from 332 cases per 100,000 children <5 years old in 1980-1991 to 17:100,000 in 1992-1995 but increased primarily in rural areas to 57.9:100,000 after a switch in Hib vaccine types. Carriage studies in 5 rural Alaska Native villages showed oropharyngeal Hib carriage as high as 9.3% in children aged 1 to 5 years; in contrast, carriage in urban Alaska Native children was <1%. CONCLUSIONS: Although Hib disease has decreased in Alaska, the rate of Hib disease and carriage in rural Alaska Natives did not decrease to the same extent as in non-Natives and urban Alaska Natives. Use of polyribosylribitol phosphate-outer-membrane protein conjugate vaccine for the first vaccine dose is critical to disease control in this population with continued transmission in infants <6 months of age. The ability to eliminate Hib carriage and disease may be affected by population characteristics, vaccination coverage, and Hib vaccine type used. This may pose a challenge to global elimination of Hib.

Antibodies to the C-terminus of the beta-amyloid precursor protein (APP): a site specific marker for the detection of traumatic axonal injury.

Antibodies to the amyloid precursor protein (APP) are commonly used to detect traumatic axonal injury (TAI). Carried by fast anterograde axoplasmic transport, APP will pool at regions of impaired transport associated with TAI. Based primarily upon commercial antibody availability, previous studies have targeted the N-terminus of APP, which, with respect to antigen detection, is suboptimally located within anterogradely transported vesicles. Recently, antibodies to the APP C-terminus, located on the external surface of anterogradely transported vesicles, have become available, allowing for the exploration of their utility in detecting TAI. To this end, rats were subjected to an impact acceleration injury, surviving 30 min to 24 h post-injury. They were then perfused, their brains sectioned and prepared for dual label immunofluorescent microscopy, single label bright field microscopy, and electron microscopy (EM). Antibodies to the APP C-terminus yielded the ready detection of intensely labeled TAI with significantly reduced diffuse background staining in comparison to antibodies to the APP N-terminus in both dual label immunofluorescent and single label bright-field approaches. EM examination of antibodies to the APP C-terminus in TAI revealed intense labeling of pooled intra-axonal vesicular profiles, confirming the anterogradely transported vesicular source of the APP seen in TAI. Interestingly, in addition to providing a technically superior approach and new detailed information on the subcellular localization of APP, antibodies to the APP C-terminus also proved more cost effective. Immunofluorescent studies of APP C-terminus immunoreactivity involved 1/3 the cost of targeting the N-terminus, while bright field APP C-terminus studies were performed for 1/20 the cost.

Invasive Haemophilus influenzae disease in Alaskan residents aged 10 years and older before and after infant vaccination programs.

CONTEXT: The introduction of Haemophilus influenzae type b (Hib) vaccination of children has led to a decline in incidence of Hib disease in young Alaskan children. However, the impact of vaccination on unimmunized Alaskan adolescents and adults has not been studied. OBJECTIVE: To characterize trends in incidence of and mortality due to invasive H influenzae disease in Alaskan residents aged 10 years and older prior to and after the introduction of a statewide Hib infant vaccination program. DESIGN AND SETTING: Population-based, descriptive correlational study conducted 1980-1996 in Alaska. SUBJECTS: One hundred twenty-nine individuals (31 Alaska Natives and 98 nonnative Alaska residents) aged 10 years and older in whom H influenzae was cultured from a normally sterile site. MAIN OUTCOME MEASURES: Incidence of H influenzae infection before (1980-1990) vs after (1991-1996) vaccination program initiation; serotype, biotype, and beta-lactamase production of isolates. RESULTS: The overall annual incidence of invasive H influenzae in those aged 10 years and older declined 33%, from 2.1 per 100,000 persons per year to 1.4 per 100,000 persons per year (P=. 03) after initiation of statewide infant Hib vaccination programs in 1991. This reduction appeared to be the result of a decrease in serotype b disease (82%; P<.001). Infection with other H influenzae serotypes and nontypeable strains increased from 0.5 per 100,000 persons per year to 1.1 per 100,000 persons per year (P=.01). Incidence declined from 4.2 per 100,000 persons per year to 1.2 per 100,000 persons per year in Alaska Natives (P=.005) and from 1.7 per 100,000 persons per year to 1.4 per 100,000 persons per year in nonnative Alaska residents (P=.37). Pneumonia (43%), sepsis (26%), and meningitis (16%) were the most common clinical presentations. Alcohol/drug abuse was comorbid in 15% of patients, while 13% of patients were pregnant women. beta-Lactamase production occurred in 35% of isolates and was stable throughout the surveillance. The overall case-fatality rate was 15%. CONCLUSION: The overall statewide incidence of invasive H influenzae infections in unimmunized persons aged 10 years and older decreased after the initiation of an infant Hib vaccine program, perhaps by decreasing Hib carriage in child reservoirs. An increase in non-serotype b strains was observed. This trend justifies the need for continued surveillance of invasive disease caused by H influenzae. JAMA. 2000.

Bronchiectasis in Alaska Native children: causes and clinical courses.

Although bronchiectasis has become a rare condition in U.S. children, it is still commonly diagnosed in Alaska Native children in the Yukon Kuskokwim Delta. The prevalence of bronchiectasis has not decreased in persons born during the 1980s as compared with those born in the 1940s. We reviewed case histories of 46 children with bronchiectasis. We observed that recurrent pneumonia was the major preceding medical condition in 85% of patients. There was an association between the lobes affected by pneumonia and the lobes affected by bronchiectasis. Eight (17%) patients had surgical resection of involved lobes. We conclude that the continued high prevalence of bronchiectasis appears to be related to extremely high rates of infant and childhood pneumonia. Pediatr Pulmonol. 2000;29:182-187. Published 2000 Wiley-Liss, Inc.

From bacteriology to biochemistry: Albert Jan Kluyver and Chester Werkman at Iowa State.

This essay explores connections between bacteriology and disciplinary evolution of biochemistry in this country during the 1930s. Many features of intermediary metabolism, a central component of biochemistry, originated as attempts to answer fundamental bacteriological questions. Thus, many bacteriologists altered their research programs to answer these questions. In doing so they changed their disciplinary focus from bacteriology to biochemistry. Chester Hamlin Werkman's (1893-1962) Iowa State career illustrates the research perspective that many bacteriologists adopted. As a junior faculty member in the Bacteriology Department in the late 1920s, Werkman faced a powerful professional dilemma: establishing a research identity that distinguished him from his colleagues with flourishing national and international reputations. His solution was to radically alter his research program from traditional bacteriology to a biochemistry program, which reflected the influence of the Dutch microbiologist/biochemist, Albert Jan Kluyver (1888-1956). Werkman was extremely successful in this career change. His laboratory made significant contributions to biochemistry, and Werkman achieved a notable degree of personal success. His career began in the shadow of his departmental bacteriological colleagues; within a decade he became the department's dominant research figure, as a biochemist. Werkman's personal success, however, had profound consequences for the disciplinary future of bacteriology at Iowa State.

The challenge of ongoing Haemophilus influenzae type B carriage and transmission in Alaska.

Cases of invasive Haemophilus influenzae type b disease in Alaskan children quickly dropped 10-fold after widespread vaccination with a conjugate vaccine (PRP-OMP) began in 1991. However, reemergence of invasive disease in 1996-97 soon followed a change to a combination diphtheria-tetanus toxoid-pertussis/H. influenzae type b vaccine which incorporates a different conjugate vaccine (HbOC). Previously unrecognized persistence of H. influenzae type b carriage in rural Alaska, coupled with characteristics of the immune response to HbOC, are the likely explanations for disease reemergence. The current vaccine recommendation--PRP-OMP for the first dose, followed by HbOC to complete the vaccination series--appears to protect Alaskan infants even in the face of continuing carriage and transmission. Successful control of invasive H. influenzae type b disease in Alaskan children will require not only appropriate immunization, but also continuing surveillance for both disease and carriage, identification of factors associated with carriage, and investigation into the feasibility of using vaccination plus antimicrobial drugs to eliminate this pathogen.