Prevalence of Helicobacter pylori among Alaskans: Factors associated with infection and comparison of urea breath test and anti-Helicobacter pylori IgG antibodies.

BACKGROUND: Helicobacter pylori is one of the most common human infections in the world, and studies in Alaska Native people, as well as other Indigenous peoples, have shown a high prevalence of this gastric infection. This study was undertaken to determine the prevalence of H. pylori infection by urea breath test (UBT) and anti- H. pylori IgG among Alaskans living in four regions of the state and to identify factors associated with infection. METHODS: A convenience sample of persons > 6 months old living in five rural and one urban Alaskan community were recruited from 1996 to 1997. Participants were asked about factors possibly associated with infection. Sera were collected and tested for anti- H. pylori IgG antibodies; a UBT was administered to participants > 5 years old. RESULTS: We recruited 710 people of whom 571 (80%) were Alaska Native and 467 (66%) were from rural communities. Rural residents were more likely to be Alaska Native compared with urban residents (P < .001). Of the 710 people, 699 (98%) had a serum sample analyzed, and 634 (97%) persons > 5 years old had a UBT performed. H. pylori prevalence was 69% by UBT and 68% by anti- H. pylori IgG. Among those with a result for both tests, there was 94% concordance. Factors associated with H. pylori positivity were Alaska Native racial status, age ≥ 20 years, rural region of residence, living in a crowded home, and drinking water that was not piped or delivered. CONCLUSIONS: Helicobacter pylori prevalence is high in Alaska, especially in Alaska Native persons and rural residents. Concordance between UBT and serology was also high in this group. Two socioeconomic factors, crowding and drinking water that was not piped or delivered, were found to be associated with H. pylori positivity.

Persistence of seropositivity among persons vaccinated for hepatitis A during infancy by maternal antibody status: 15-year follow-up.

UNLABELLED: The effect of passively transferred maternal antibody to hepatitis A virus (anti-HAV) on the duration of seropositivity after hepatitis A vaccination during infancy and early childhood is unclear. We obtained levels of anti-HAV at intervals through age 15-16 years among three groups of Alaskan Native children who initiated a two-dose inactivated hepatitis A vaccination series at ages 6 months (group 1), 12 months (group 2), and 15 months (group 3), each group randomized according to maternal anti-HAV status. Seropositivity (anti-HAV ≥20 mIU/mL) 30 years after the second vaccine dose among the three groups was predicted using a random effects model. One hundred eighty-three children participated in the study; follow-up did not differ significantly by vaccine group or maternal anti-HAV status. Although the frequency of seropositivity among all participants through age 10 years was high (100% among groups 2 and 3 and >90% among group 1), there was a decrease thereafter through age 15-16 years among group 1 children, who initiated vaccination at age 6 months (50%-75%), and among maternal anti-HAV-positive children in groups 2 and 3 (67%-87%), who initiated vaccination at ages 12 months and 15 months, respectively. Nonetheless, the model indicated that anti-HAV seropositivity should persist for ≥30 years after vaccination in 64% of all participants; among those seropositive at age 15-16 years, 84% were predicted to remain so for ≥30 years. CONCLUSION: Most children vaccinated during early childhood available for sampling maintained seropositivity through age 15-16 years; however, seropositivity was less frequent among those starting vaccination at age 6 months and among maternal antibody-positive participants who started vaccination at age 12 months or 15 months; overall, our findings support current vaccine recommendations and continued follow-up of this cohort.

Declines in traditional marine food intake and vitamin D levels from the 1960s to present in young Alaska Native women.

OBJECTIVE: To measure the trends in traditional marine food intake and serum vitamin D levels in Alaska Native women of childbearing age (20-29 years old) from the 1960s to the present. DESIGN: We measured a biomarker of traditional food intake, the δ15N value, and vitamin D level, as 25-hydroxycholecalciferol (25(OH)D3) concentration, in 100 serum samples from 20-29-year-old women archived in the Alaska Area Specimen Bank, selecting twenty-five per decade from the 1960s to the 1990s. We compared these with measurements of red-blood-cell δ15N values and serum 25(OH)D3 concentrations from 20-29-year-old women from the same region collected during the 2000s and 2010s in a Center for Alaska Native Health Research study. SETTING: The Yukon Kuskokwim Delta region of south-west Alaska. SUBJECTS: Alaska Native women (n 319) aged 20-29 years at the time of specimen collection. RESULTS: Intake of traditional marine foods, as measured by serum δ15N values, decreased significantly each decade from the 1960s through the 1990s, then remained constant from the 1990s through the present (F 5,306=77·4, P<0·0001). Serum vitamin D concentrations also decreased from the 1960s to the present (F 4,162=26·1, P<0·0001). CONCLUSIONS: Consumption of traditional marine foods by young Alaska Native women dropped significantly between the 1960s and the 1990s and was associated with a significant decline in serum vitamin D concentrations. Studies are needed to evaluate the promotion of traditional marine foods and routine vitamin D supplementation during pregnancy for this population.

Hepatocellular Carcinoma Risk in Alaska Native Children and Young Adults with Hepatitis B Virus: Retrospective Cohort Analysis.

OBJECTIVES: To evaluate the hepatocellular carcinoma (HCC) risk in Alaska Native children and young adults with hepatitis B virus (HBV). STUDY DESIGN: Retrospective analysis of a population-based cohort of Alaska Native persons with HBV followed during 1982-2012. All individuals with HBV were offered HCC screening regardless of age using alpha-fetoprotein every 6 months; persons with an elevated alpha-fetoprotein or persons at high-risk for HCC, such as cirrhosis, family history of HCC, were offered ultrasound. We calculated the HCC incidence/1000 person-years from date of cohort entry until death, diagnosis of HCC, or attaining the age of 40 years (males) or 50 years (females). RESULTS: We followed 1083 subjects with HBV (56% male) comprising 5 genotypes (A2 [12.5%], B6 [1.7%], C [5.3%], D [49.7%], F1 [18.6%], unknown [12.4%]) for a median of 23.4 years/person. We observed 22 HCC cases (incidence/1000 person-years follow-up: 1.0); 19 HCC cases among persons with genotype F1. There was no significant difference in HCC incidence between males (1.4) and females (0.6). The HCC incidence was significantly higher for persons with genotype F1 (4.4) compared with genotype A2 (0.4) and D (0.2) and remained higher among persons with HBV genotype F1 excluding persons with HCC family history/cirrhosis (1.9). CONCLUSIONS: Alaska Native children and young adults with HBV genotype F1 are at high risk for HCC and should receive HCC surveillance. For males <40 years of age and females <50 years of age with HBV in regions of the world with a high genotype F prevalence, testing/confirming genotype F can identify persons who could benefit from HCC surveillance.

Long-term immunogenicity of hepatitis A virus vaccine in Alaska 17 years after initial childhood series.

The Centers for Disease Control and Prevention recommends hepatitis A virus (HAV) vaccination for all children at age 1 year and for high-risk adults. The vaccine is highly effective; however, protection duration is unknown. We report HAV antibody concentrations 17 years after childhood immunization, demonstrating that protective antibody levels remain and have stabilized over the past 7 years.

Persistence of hepatitis A vaccine induced seropositivity in infants and young children by maternal antibody status: 10-year follow-up.

UNLABELLED: Persistence of seropositivity conferred by hepatitis A vaccine administered to children <2 years of age is unknown and passively transferred maternal antibodies to hepatitis A virus (maternal anti-HAV) may lower the infant's immune response to the vaccine. One hundred ninety-seven infants and young children were randomized into three groups to receive a two-dose hepatitis A vaccine: group 1 at 6 and 12 months, group 2 at 12 and 18 months, and group 3 at 15 and 21 months of age. Within each group, infants were randomized by maternal anti-HAV status. Anti-HAV levels were measured at 1 and 6 months and at 3, 5, 7, and 10 years after the second dose of hepatitis A vaccination. Children in all groups had evidence of seroprotection (>10 mIU/mL) at 1 month after the second dose. At 10 years, all children retained seroprotective anti-HAV levels except for only 7% and 11% of children in group 1 born to anti-HAV-negative and anti-HAV-positive mothers, respectively, and 4% of group 3 children born to anti-HAV-negative mothers. At 10 years, children born to anti-HAV-negative mothers in group 3 had the highest geometric mean concentration (GMC) (97 mIU/mL; 95% confidence interval, 71-133 mIU/mL) and children born to anti-HAV-positive mothers in group 1 had the lowest GMC (29 mIU/mL; 95% confidence interval, 20-40 mIU/mL). Anti-HAV levels through 10 years of age correlated with initial peak anti-HAV levels (tested at 1 month after the second dose). CONCLUSION: The seropositivity induced by hepatitis A vaccine given to children <2 years of age persists for at least 10 years regardless of presence of maternal anti-HAV.

Elimination of hepatocellular carcinoma and acute hepatitis B in children 25 years after a hepatitis B newborn and catch-up immunization program.

UNLABELLED: Alaska Native people experience the highest rates of acute and chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) in the United States. We examined the effect of a universal newborn immunization with hepatitis B vaccine and mass population screening immunization program initiated in 1984 on rates of HBV and HCC in children 25 years later. During this time, the population of Alaska Native people grew from an estimated 75,000 to 130,000 persons. A surveillance system to detect acute HBV infection in Alaska Native facilities was established in 1981. Cases of HCC in children under 20 years of age were identified using a National Cancer Institute (NCI)-funded Cancer Registry established in 1969 coupled with an active surveillance program of screening persons with chronic HBV semiannually for alpha-fetoprotein since 1982. The incidence of acute symptomatic HBV infection in persons <20 years of age fell from cases 19/100,000 in 1981-1982 to 0/100,000 in 1993-1994. No cases of acute HBV have occurred in children since 1992. The incidence of HCC in persons <20 years decreased from 3/100,000 in 1984-1988 to zero in 1995-1999 and no cases have occurred since 1999. The number of identified hepatitis B surface antigen-positive children <20 years in the Alaska Native population declined from 657 in 1987 to two in 2008. CONCLUSION: Universal newborn vaccination coupled with mass screening and immunization of susceptible Alaska Natives has eliminated HCC and acute symptomatic HBV infection among Alaska Native children and this approach is the best way to prevent HBV-related disease in children.

Transplacental Respiratory Syncytial Virus and Influenza Virus Antibody Transfer in Alaska Native and Seattle Mother-Infant Pairs.

BACKGROUND: Alaska Native (AN) infants are at risk for severe disease due to respiratory syncytial virus (RSV) and influenza. Maternal immunization protects young infants through transplacental antibody transfer. RSV- and influenza-specific transplacental antibody transfer in mother-infant pairs has not previously been evaluated in the AN population. METHODS: Serum samples collected during pregnancy and at birth from AN mother-infant pairs in the Yukon-Kuskokwim Delta region (YKD) of Alaska (2000-2011; n = 75) and predominantly white pairs in Seattle, Washington (2014-2016; n = 57), were tested for RSV and influenza antibody using a microneutralization and hemagglutination inhibition assay, respectively, and compared between sites. RESULTS: Mean RSV antibody concentrations in pregnant women in YKD and Seattle were similar (log2 RSV antibody 10.6 vs 10.7, P = .86), but cord blood RSV antibody concentrations were significantly lower in infants born to mothers in YKD compared with Seattle (log2 RSV antibody 11.0 vs 12.2, P < .001). Maternal and cord blood influenza antibody concentrations were lower for women and infants in YKD compared with Seattle for all 4 influenza antigens tested (all P < .05). The mean cord to maternal RSV antibody transfer ratio was 1.15 (standard deviation [SD], 0.13) in mother-infant pairs in Seattle compared with 1.04 (SD, 0.08) in YKD. Mean cord blood to maternal antibody transfer ratios for influenza antigens ranged from 1.22 to 1.42 in Seattle and from 1.05 to 1.59 in YKD. CONCLUSIONS: Though the transplacental antibody transfer ratio was high (>1.0) for both groups, transfer ratios for RSV antibody were significantly lower in AN mother-infant pairs. Further studies are needed to elucidate the impact of lower transplacental antibody transfer on infant disease risk in rural Alaska.Alaska Native and continental US mother-infant pairs have high transplacental antibody transfer ratios (>1.0) for influenza and respiratory syncytial virus, but anti-respiratory syncytial virus antibody levels are significantly lower in Alaska Native pairs than in those from the continental US.

Viral respiratory infections in hospitalized and community control children in Alaska.

Respiratory syncytial virus (RSV) in Alaska Native children from the Yukon Kuskokwim (YK) Delta is associated with a hospitalization rate five times higher than that reported for the general US child population. The role of other viral respiratory pathogens has not been studied in this population. YK Delta children <3 years of age hospitalized with respiratory infections and same aged community control children were prospectively enrolled between October 2005 and September 2007. Polymerase chain reaction detection of viruses was performed on nasopharyngeal samples. Characteristics of hospitalized and asymptomatic control children were analyzed. From October 2005 to September 2007, 440 hospitalized and 425 control children were analyzed. Respiratory viruses were detected in 90% (395) of hospitalized children: 194 (44%) rhinovirus, 131 (30%) adenovirus, 102 (23%) RSV, 77 (18%) para influenza viruses (PIV), 66 (15%) human metapneumovirus (hMPV), 23 (5%) influenza, and 25 (6%) coronavirus. Fifty-two percent (221) of control children had a virus detected, most commonly rhinovirus (33%), and adenovirus (16%). RSV, PIV, hMPV, and influenza were significantly more common in hospitalized cases than control children, but rhinovirus, adenovirus, and coronavirus were not. RSV and hMPV were associated with higher severity of illness. In this study, RSV remains the most important virus associated with respiratory hospitalization, although hMPV and PIV were also common. RSV and hMPV were associated with more severe illness. Rhinovirus and adenovirus were detected in two-thirds of hospitalized children, but their frequent detection in control children made their role in respiratory hospitalization uncertain.

Diabetes prevalence, incidence, complications and mortality among Alaska Native people 1985-2006.

OBJECTIVES: To examine trends in diabetes prevalence, incidence, complications and mortality between 1985 and 2006 among Alaska Native people. STUDY DESIGN: We used data from the population-based Alaska Native Diabetes Registry, which includes all people who receive care in the Alaska Tribal Health System. METHODS: We compared the periods of 1986-1990 and 2002-2006 for diabetes-related amputations, renal replacement and mortality using Poisson regression. Complications and mortality data were examined for trends using Poisson regression. Survival analyses for those diagnosed since 31 December 1985 were performed using the Cox proportional hazard model. RESULTS: Age-adjusted diabetes prevalence increased from 17.3 in 1985 to 47.6/1,000 in 2006. The number of Alaska Native people living in Alaska with diabetes increased from 610 in 1985 to 3,386 in 2006. Diabetes incidence rates have also increased. Comparing age-adjusted rates for the 5-year periods 1986-1990 and 2002-2006, amputations decreased from 5.3 to 2.6/1,000, renal replacement decreased from 3.3 to 1.2/1,000 and mortality decreased from 41.7 to 33.2/1,000. Yearly analyses showed a downward trend for amputations, renal replacement and mortality rates. Survival analyses showed a significantly higher hazard ratio for any amputations, major amputations and renal replacement for the earlier time period compared to the most recent time period. CONCLUSIONS: An increase in risk factors, awareness, funding and case-finding may be contributing to the increase in prevalence and incidence of diagnosed diabetes. While diabetes prevalence and incidence are increasing among Alaska Native people, our results suggest that even in remote, rural areas, complications and mortality can be reduced.

Increasing non-susceptibility to antibiotics within carried pneumococcal serotypes - Alaska, 2008-2015.

BACKGROUND: In Alaska, while introduction of 13-valent pneumococcal conjugate vaccine led to declines in invasive pneumococcal disease, carriage prevalence remained stable because of replacement with non-vaccine serotypes. We assessed antibiotic non-susceptibility of carried pneumococci during serotype redistribution, determined the contributions of within-serotype shifts, and assessed factors that could explain changes in non-susceptibility. METHODS: Each year from 2008 to 2015, at multiple sites in Alaska, we collected nasopharyngeal swabs and completed surveys for a convenience sample of participants. Pneumococcal serotyping and antimicrobial susceptibility testing for penicillin and erythromycin were performed. We described changes in non-susceptibility of isolates from 2008-2011 to 2012-2015, and assessed the contributions of serotype redistribution and within-serotype changes in non-susceptibility by comparing observed data to modeled data removing either factor. We used weighted logistic regression to assess whether reported risk factors could explain changes over time in non-susceptibility within serotypes. RESULTS: From 2008-2011 to 2012-2015, the overall proportion of isolates non-susceptible to penicillin or erythromycin increased by 3%, from 23% (n = 1,183) to 26% (n = 1,589; P < 0.05). However, a decrease of 3% would be expected if serotype redistribution occurred without within-serotype changes in non-susceptibility. Standardization by either factor produced hypothetical data significantly different to observed data. Within serotypes, the average annual increase in odds of non-susceptibility to penicillin or erythromycin was 1.08 (95% CI 1.05-1.11). Recent antibiotic exposure, urban residence and increased household size of participants predicted isolate non-susceptibility but did not explain the increase over time. DISCUSSION: An overall increase in non-susceptibility of carried pneumococcal isolates to penicillin or erythromycin resulted from increases in non-susceptibility within serotypes, which outweighed a protective effect of serotype redistribution. Characterization of emerging resistant clones within carried non-vaccine serotypes, including risk factors for colonization and disease, would support disease prevention efforts and inform vaccine strategies.

Immunogenicity and reactogenicity of pneumococcal polysaccharide and conjugate vaccines in alaska native adults 55-70 years of age.

BACKGROUND: Vaccination with conjugate vaccines stimulates T cell-dependent immunity, whereas vaccination with polysaccharide vaccines does not. Thus, vaccination with the 7-valent pneumococcal conjugate vaccine (PCV7) followed by the 23-valent pneumococcal polysaccharide vaccine (PPV23) may offer better protection against invasive pneumococcal disease for older adults than does vaccination with PPV23 alone, which is what is currently recommended. METHODS: Alaska Native adults 55-70 years of age with no previous pneumococcal vaccination were randomized to receive (1) PPV23, (2) PCV7 followed 2 months later by PPV23, or (3) PCV7 followed 6 months later by PPV23. Participants recorded reactions after each vaccination. Serum samples collected during the period from May 2002 through February 2003 were tested for serotype-specific immunoglobulin G (IgG) and for opsonophagocytic activity (OPA) against serotypes 1, 4, 6B, 14, and 19F. RESULTS: Vaccination with PCV7 was well tolerated, but persons receiving PCV7 followed by PPV23 reported more local reactions than those receiving only PPV23. All reactions resolved spontaneously within 72 h of receiving vaccine. The geometric mean IgG concentrations of and the median OPA titers to serotypes 4, 6B, 14, and 19F increased in all groups after 1 dose of either PCV7 or PPV23. Serotype-specific geometric mean IgG concentrations and median OPA titers did not differ between any of the groups after vaccination with PPV23, regardless of whether they had previously received PCV7. CONCLUSIONS: In this study, PCV7 given 2 or 6 months before PPV23 was well tolerated but did not improve immune response to PPV23 in older Alaska Native adults.

Clearance of hepatitis B e antigen in patients with chronic hepatitis B and genotypes A, B, C, D, and F.

BACKGROUND & AIMS: Persistence of hepatitis B e antigen (HBeAg) in chronic hepatitis B has been associated with increased risk for development of cirrhosis and hepatocellular carcinoma. Five hepatitis B virus genotypes were identified in Alaska Native persons; we analyzed clearance of HBeAg by age and genotype. METHODS: In this prospective cohort study, 1158 Alaska Native persons throughout Alaska were tested serially for HBeAg for a median of 20.5 years and were genotyped. Initial and final HBeAg-positive specimens, time to clearance, age at clearance, and subsequent HBeAg results were analyzed for persons initially HBeAg-positive. Subsequent HBeAg results were analyzed for persons initially negative. RESULTS: Genotypes A, B, C, D, and F were identified. Genotype C persons initially HBeAg-positive were more likely than those with other genotypes to be positive on initial and final specimens (P < .001 for each) and time to HBeAg clearance was longer (P < .001). Age at which 50% of persons cleared HBeAg was <20 years for those infected with genotypes A, B, D, and F and 47.8 years in genotype C (P < .001). After losing HBeAg, those with genotypes C and F were more likely to revert to the HBeAg-positive state (P < .001). CONCLUSIONS: Genotype may have a strong effect on mode of transmission and outcome. Genotype C may have been responsible for most perinatal transmission, given that seroconversion from HBeAg occurs decades later than in other genotypes.

The relative invasive disease potential of Streptococcus pneumoniae among children after PCV introduction: A systematic review and meta-analysis.

OBJECTIVES: Burden of pneumococcal disease depends on the prevalence and invasive disease potential of serotypes. We aimed to estimate the invasive disease potential of serotypes in children under 5 years of age by combining data from different settings with routine immunisation with pneumococcal conjugate vaccines (PCV). METHODS: We conducted a systematic review, supplemented by unpublished data, to identify data on the frequency of pneumococcal serotypes in carriage and invasive pneumococcal disease (IPD). We estimated the invasive disease potential of serotypes as the ratio of IPD in relation to carriage (odds ratio and 95%CI) compared with 19A (reference serotype) by meta-analysis. We report results based on a random effects model for children aged 0-23, 24-29, and 0-59 months and by invasive clinical syndromes. RESULTS: In comparison with 19A, serotypes 1, 7F, and 12F had a significantly higher invasive disease potential in children aged 0-23 and 0-59 months for all IPD and clinical syndromes (OR > 5). Several non-vaccine types (NVTs) (6C, 15A, 15BC, 16F, 23B, in these two age groups) had a lower invasive disease potential than 19A (OR 0.1-0.3). NVTs 8, 12F, 24F, and 33F were at the upper end of the invasiveness spectrum. CONCLUSIONS: There is substantial variation among pneumococcal serotypes in their potential to cause IPD and disease presentation, which is influenced by age and time after PCV introduction. Surveillance of IPD and carriage is critical to understand the expected effectiveness of current PCVs (in the longer term) and guide the development of future vaccines.

Respiratory syncytial virus season and hospitalizations in the Alaskan Yukon-Kuskokwim Delta.

From 1993 to 1996, Alaska Native infants younger than 1 year of age from the Yukon-Kuskokwim Delta region in Alaska experienced a respiratory syncytial virus (RSV) hospitalization rate 5 times higher than the U.S. general infant population rate. This article describes the trends in hospitalization and prolonged annual season of RSV hospitalizations in Yukon-Kuskokwim children from 1993 to 2004 and discusses factors associated with high rates of RSV hospitalization and the impact of interventions to decrease RSV hospitalizations in this population.

Invasive pneumococcal disease caused by nonvaccine serotypes among alaska native children with high levels of 7-valent pneumococcal conjugate vaccine coverage.

CONTEXT: With routine childhood vaccination using heptavalent pneumococcal conjugate vaccine, one concern has been the potential for emergence and expansion of replacement disease caused by serotypes not contained in the heptavalent conjugate vaccine. OBJECTIVE: To determine whether replacement disease is associated with the overall decline in invasive pneumococcal disease among Alaska Native children. DESIGN, SETTING, AND PATIENTS: Alaska statewide longitudinal population-based laboratory surveillance of invasive Streptococcus pneumoniae infections from January 1, 1995, through December 31, 2006. MAIN OUTCOME MEASURES: Incidence and types of pneumococcal disease in children younger than 2 years. RESULTS: In the first 3 years after introduction of routine vaccination with heptavalent pneumococcal conjugate vaccine, overall invasive pneumococcal disease decreased 67% in Alaska Native children younger than 2 years (from 403.2 per 100,000 in 1995-2000 to 134.3 per 100,000 per year in 2001-2003, P<.001). However, between 2001-2003 and 2004-2006, there was an 82% increase in invasive disease in Alaska Native children younger than 2 years to 244.6/100,000 (P = .02). Since 2004, the invasive pneumococcal disease rate caused by nonvaccine serotypes has increased 140% compared with the prevaccine period (from 95.1 per 100,000 in 1995-2000 to 228.6 in 2004-2006, P = .001). During the same period, there was a 96% decrease in heptavalent vaccine serotype disease. Serotype 19A accounted for 28.3% of invasive pneumococcal disease among Alaska children younger than 2 years during 2004-2006. There was no significant increase in nonvaccine disease in non-Native Alaska children younger than 2 years. CONCLUSIONS: Alaska Native children are experiencing replacement invasive pneumococcal disease with serotypes not covered by heptavalent pneumococcal conjugate vaccine. The demonstration of replacement invasive pneumococcal disease emphasizes the importance of ongoing surveillance and development of expanded valency vaccines.

Decline in respiratory syncytial virus hospitalizations in a region with high hospitalization rates and prolonged season.

BACKGROUND: During 1993 to 1996, Alaska Native infants <1 year of age from the Yukon Kuskokwim (YK) Delta in Alaska experienced a respiratory syncytial virus (RSV) hospitalization rate 5 times the U.S. general infant population rate. We describe trends in lower respiratory tract infection (LRTI) and RSV hospitalizations in YK children from 1994 to 2004. METHODS: We abstracted hospital dates, RSV test results and clinical information from the hospital records for YK children <3 years of age hospitalized between July 1994 and June 2004. RESULTS: : The RSV hospitalization rate in YK Delta children <1 year of age decreased from 178 per 1000 infants per year (1994-1997) to 104 per 1000 infants per year (2001-2004) (P < 0.001), and the RSV hospitalization rate for premature infants decreased from 317 to 123 per 1000 infants per year (P < 0.001). The risk reduction for RSV hospitalization was greater in premature (relative risk, 0.39) than in term infants (relative risk, 0.60; P = 0.04). The rate of non-RSV LRTI hospitalizations increased from 153 to 215 per 1000 infants per year (P < 0.001). The median RSV season length was 30.5 weeks. Pneumonia was diagnosed in more than half of RSV admissions. CONCLUSIONS: In YK infants, the RSV hospitalization rate decreased by one-third between 1994 and 2004; however, the overall LRTI hospitalization rate did not change. The median RSV season was twice as long as for the U.S. population. Palivizumab prophylaxis may be responsible for the larger decrease in the RSV hospitalization rate among premature infants; however, the 2001-2004 RSV hospitalization rate among YK infants remained 3 times higher than the U.S. infant rate.

Antibody levels and protection after hepatitis B vaccination: results of a 15-year follow-up.

BACKGROUND: The duration of protection afforded by hepatitis B vaccination is unknown. OBJECTIVE: To determine antibody persistence and protection from hepatitis B virus (HBV) infection. DESIGN: Prospective cohort study. SETTING: 15 villages in southwest Alaska. PARTICIPANTS: 1578 Alaska Natives vaccinated at age 6 months or older. INTERVENTION: During 1981-1982, participants received 3 doses of plasma-derived hepatitis B vaccine. This cohort was followed annually over the first 11 years, and 841 (53%) persons were tested at 15 years. MEASUREMENTS: Antibody to hepatitis B surface antigen (anti-HBs), markers of HBV infection, and testing to identify HBV variants. RESULTS: Levels of anti-HBs in the cohort decreased from a geometric mean concentration of 822 mIU/mL after vaccination to 27 mIU/mL at 15 years. Initial anti-HBs level, older age at vaccination, and male sex were associated with persistence of higher anti-HBs levels at 15 years when analyzed by a longitudinal linear mixed model. After adjustment for initial anti-HBs level and sex, those vaccinated at age 6 months to 4 years had the lowest anti-HBs level at 15 years. Asymptomatic breakthrough infections were detected in 16 participants and occurred more frequently in persons who did not respond to vaccination than those who responded (P = 0.01). Among infected persons with viremia, 2 were infected with wild-type HBV and 4 had HBV surface glycoprotein variants, generally accompanied by wild-type HBV. LIMITATIONS: The loss of participants to follow-up at 15 years was 47%. However, characteristics of persons tested were similar to those of persons lost to follow-up. CONCLUSIONS: Hepatitis B vaccination strongly protected against infection for at least 15 years in all age groups. Antibody levels decreased the most among persons immunized at 4 years of age or younger.

A survey of knowledge, attitudes, and practices towards skin and soft tissue infections in rural Alaska.

BACKGROUND: Community-acquired methicillin-resistant Staphylococcus aureus and methicillin-sensitive S. aureus infections are common to south-western Alaska and have been associated with traditional steambaths. More than a decade ago, recommendations were made to affected communities that included preventive skin care, cleaning methods for steambath surfaces, and the use of protective barriers while in steambaths to reduce the risk of S. aureus infection. OBJECTIVE: A review of community medical data suggested that the number of skin infection clinical encounters has increased steadily over the last 3 years and we designed a public health investigation to seek root causes. STUDY DESIGN: Using a mixed methods approach with in-person surveys, a convenience sample (n=492) from 3 rural communities assessed the range of knowledge, attitudes and practices concerning skin infections, skin infection education messaging, prevention activities and home self-care of skin infections. RESULTS: We described barriers to implementing previous recommendations and evaluated the acceptability of potential interventions. Prior public health messages appear to have been effective in reaching community members and appear to have been understood and accepted. We found no major misconceptions regarding what a boil was or how someone got one. Overall, respondents seemed concerned about boils as a health problem and reported that they were motivated to prevent boils. We identified current practices used to avoid skin infections, such as the disinfection of steambaths. We also identified barriers to engaging in protective behaviours, such as lack of access to laundry facilities. CONCLUSIONS: These findings can be used to help guide public health strategic planning and identify appropriate evidence-based interventions tailored to the specific needs of the region.

Cost-effectiveness analysis of hepatocellular carcinoma screening by combinations of ultrasound and alpha-fetoprotein among Alaska Native people, 1983-2012.

BACKGROUND: The American Association for the Study of Liver Diseases (AASLD) recommends semi-annual hepatocellular carcinoma (HCC) screening using ultrasound (US) in persons with chronic hepatitis B (CHB) virus infection at high risk for HCC such as Asian males aged ≥40 years and Asian females aged ≥50 years. OBJECTIVE: To analyse the cost-effectiveness of 2 HCC screening methods in the Alaska Native (AN) health system: US-alone, or screening by alpha-fetoprotein (AFP) initially and switching to US for subsequent screenings if AFP >10 ng/mL (AFP→US). DESIGN: A spreadsheet-based model was developed for accounting the costs of 2 hypothetical HCC screening methods. We used epidemiologic data from a cohort of 839 AN persons with CHB who were offered HCC screening by AFP/US semi-annually during 1983-2012. We assumed that compared with AFP→US, US-alone identifies 33% more tumours at an early stage (defined as a single tumour ≤5 cm or ≤3 tumours ≤3 cm in diameter). Years of life gained (YLG) attributed to screening was estimated by comparing additional years of survival among persons with early- compared with late-stage tumours. Screening costs were calculated using Medicare reimbursement rates in 2012. Future screening costs and YLG were projected over a 30-year time horizon using a 3% discount rate. RESULTS: The total cost of screening for the cohort by AFP→US would have been approximately $357,000 ($36,000/early-stage tumour detected) compared to $814,000 ($59,000/early-stage tumour detected) by US-alone. The AFP→US method would have yielded an additional 27.8 YLG ($13,000/YLG) compared with 38.9 YLG ($21,000/YLG) for US-alone. Screening by US-alone would incur an additional $114,000 per extra early-tumour detected compared with AFP→US and $41,000 per extra YLG. CONCLUSIONS: Although US-alone HCC screening might have yielded more YLG than AFP→US, the reduced costs of the AFP→US method could expand access to HCC screening in resource constrained settings.