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.

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.

Improving human health in the Arctic: the expanding role of the Arctic Council's Sustainable Development Working Group.

Human health is now a critical component of the Arctic Council's sustainable development program. The newly formed Arctic Human Health Expert Group (AHHEG), a subsidiary body of experts within the Sustainable Development Working Group (SDWG), will focus on identifying human health priorities that will improve the health of Arctic residents; engage experts in the field to evaluate possible actions; strengthen co-operation and collaboration between Arctic Council working groups and other Arctic co-operatives; and promote the translation of research into actions that will improve the health of Arctic peoples.

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.

Human Seroprevalence to 11 Zoonotic Pathogens in the U.S. Arctic, Alaska.

Background: Due to their close relationship with the environment, Alaskans are at risk for zoonotic pathogen infection. One way to assess a population's disease burden is to determine the seroprevalence of pathogens of interest. The objective of this study was to determine the seroprevalence of 11 zoonotic pathogens in people living in Alaska. Methods: In a 2007 avian influenza exposure study, we recruited persons with varying wild bird exposures. Using sera from this study, we tested for antibodies to Cryptosporidium spp., Echinococcus spp., Giardia intestinalis, Toxoplasma gondii, Trichinella spp., Brucella spp., Coxiella burnetii, Francisella tularensis, California serogroup bunyaviruses, and hepatitis E virus (HEV). Results: Eight hundred eighty-seven persons had sera tested, including 454 subsistence bird hunters and family members, 160 sport bird hunters, 77 avian wildlife biologists, and 196 persons with no wild bird exposure. A subset (n = 481) of sera was tested for California serogroup bunyaviruses. We detected antibodies to 10/11 pathogens. Seropositivity to Cryptosporidium spp. (29%), California serotype bunyaviruses (27%), and G. intestinalis (19%) was the most common; 63% (301/481) of sera had antibodies to at least one pathogen. Using a multivariable logistic regression model, Cryptosporidium spp. seropositivity was higher in females (35.7% vs. 25.0%; p = 0.01) and G. intestinalis seropositivity was higher in males (21.8% vs. 15.5%; p = 0.02). Alaska Native persons were more likely than non-Native persons to be seropositive to C. burnetii (11.7% vs. 3.8%; p = 0.005) and less likely to be seropositive to HEV (0.4% vs. 4.1%; p = 0.01). Seropositivity to Cryptosporidium spp., C. burnetii, HEV, and Echinococcus granulosus was associated with increasing age (p ≤ 0.01 for all) as was seropositivity to ≥1 pathogen (p < 0.0001). Conclusion: Seropositivity to zoonotic pathogens is common among Alaskans with the highest to Cryptosporidium spp., California serogroup bunyaviruses, and G. intestinalis. This study provides a baseline for use in assessing seroprevalence changes over time.

Changing epidemiology of invasive pneumococcal disease among White Mountain Apache persons in the era of the pneumococcal conjugate vaccine.

BACKGROUND: Prior to the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7), the rate of invasive pneumococcal disease (IPD) was 8-fold higher among White Mountain Apache persons of all ages than it was among the general US population, . We aimed to assess the impact of PCV7 and 23-valent pneumococcal polysaccharide vaccine on the rate of IPD among White Mountain Apache persons. METHODS: From 1991 through 2006, we conducted active laboratory- and population-based surveillance among Native American residents of the White Mountain Apache reservation. Charts were reviewed and pneumococcal isolates were collected for serotype testing. Three time periods were defined: the pre-PCV7 baseline period (1991-1997), the PCV7 efficacy trial period (1998-2000), and the PCV7 routine-use period (2001-2006). RESULTS: We identified 246 cases of IPD; the mean annual IPD rate fell from 126 cases per 100,000 person-years in the period 1991-1997 to 87 cases per 100,000 person-years in the period 2001-2006 (p = .01). The rate of IPD attributable to PCV7 serotypes of Streptococcus pneumoniae decreased by 252 cases per 100,000 person-years (92%) among children aged <5 years, and that attributable to non-PCV7 serotypes of S. pneumoniae decreased by 87 cases per 100,000 person-years (44%) among children aged <5 years. Among adults, the rate of IPD remained unchanged; PCV7 serotypes of S. pneumoniae accounted for only 25% of adult cases during the period 1991-1997. CONCLUSIONS: Since the introduction of PCV7, the rate of IPD among White Mountain Apache children aged <5 years has decreased to the lowest rate ever (122 cases per 100,000 person-years), but it remains 5.7-fold greater than the rate of IPD among children in the general US population. In contrast to some other high-risk populations, there is no evidence of non-vaccine-type replacement disease in this age group. Among White Mountain Apache adults, the rate of IPD remains substantially higher than that observed in the general US population. Vaccines with broader serotype coverage are needed to further reduce the disparity in the rate of IPD between the White Mountain Apache and general US populations.

Impact of conjugate vaccine on transmission of antimicrobial-resistant Streptococcus pneumoniae among Alaskan children.

BACKGROUND: The impact of heptavalent pneumococcal conjugate vaccine (PCV7) on transmission of antimicrobial-resistant Streptococcus pneumoniae is an important concern for countries considering PCV7 introduction. METHODS: Every winter from 2000 to 2004, as PCV7 was routinely introduced, we obtained nasopharyngeal swabs for pneumococcal culture, serotyping, and susceptibility testing from 150 children aged 3-59 months at each of 3 Anchorage, Alaska clinics. We assessed risk factors for pneumococcal carriage, including vaccination status and antimicrobial use. RESULTS: Between 2000 and 2004, 2250 nasopharyngeal swabs from 2061 infants and children were collected. The proportion of children receiving > or = 1 PCV7 vaccination increased from 0 to 89%, whereas overall pneumococcal carriage remained stable (38% versus 41%, respectively). Among S. pneumoniae carriers, we observed declines in carriage of PCV7 serotypes (from 54% to 10%, P < 0.01) and trimethoprim-sulfamethoxazole nonsusceptible strains (44% to 16%, P < 0.01), but not in PCN-nonsusceptible strains (36% versus 37%). Among PCN-nonsusceptible types, the proportion of serotype 19A strains increased from 10% to 32% (P = 0.0002). Recent beta-lactam use was stable throughout the period (29% overall), whereas trimethoprim-sulfamethoxazole use declined from 6% to 2% (P = 0.02). CONCLUSIONS: PCV7 vaccination in the first 5 years did not affect overall pneumococcal carriage, but was associated with a shift in serotype distribution from PCV7 types to non-PCV7 types. With persistent pressure of some antimicrobials, reductions in carriage of antimicrobial nonsusceptible PCV7 types may be offset by increases in carriage of nonsusceptible non-PCV7 types.

The relationship between previous fluoroquinolone use and levofloxacin resistance in Helicobacter pylori infection.

The relationship between prior fluoroquinolone use and levofloxacin resistance in Helicobacter pylori infection is unknown. Among 125 enrolled patients, 8.8% had H. pylori isolates that were resistant to levofloxacin. Levofloxacin resistance was associated with any prior fluoroquinolone use over the previous 10 years and with the total number of fluoroquinolone courses prescribed (P<.001).

The international polar year 2007-2008; the Arctic human health legacy.

Life expectancy in Arctic populations has greatly improved over the last 50 years. Much of this improvement can be attributed to health research that has resulted in a reduction in morbidity and mortality from infectious diseases, such as tuberculosis, and the vaccine-preventable diseases of childhood. However, despite these improvements in health indicators of Arctic residents, life expectancy and infant mortality remain higher in indigenous Arctic residents in the US Arctic, northern Canada, and Greenland when compared to Arctic residents of Nordic countries. The International Polar Year (IPY) represents a unique opportunity to focus world attention on Arctic human health and to further stimulate Circumpolar cooperation on emerging Arctic human health concerns. The Arctic Human Health Initiative (AHHI) is an Arctic Council IPY initiative that aims to build and expand on existing Arctic Council and International Union for Circumpolar Health (IUCH) human health research activities. The human health legacy of the IPY will be increased visibility of the human health concerns of Arctic communities, revitalization of cooperative Arctic human health research focused on those concerns, the development of health policies based on research findings, and the subsequent implementation of appropriate interventions, prevention and control measures at the community level.

The International Polar year 2007-2008; the Arctic human health legacy.

Life expectancy in Arctic populations has greatly improved over the last 50 years. Much of this improvement can be attributed health research that has resulted in a reduction in morbidity and mortality from infectious diseases, such as tuberculosis, and the vaccine-preventable diseases of childhood. However, despite these improvements in health indicators of Arctic residents, life expectancy and infant mortality remain higher in indigenous Arctic residents in the US Arctic, northern Canada, and Greenland when compared to Arctic residents of Nordic countries. The International Polar Year (IPY) represents a unique opportunity to focus world attention on Arctic human health and to further stimulate Circumpolar cooperation on emerging Arctic human health concerns. The Arctic Human Health Initiative (AHHI) is an Arctic Council IPY initiative that aims to build and expand on existing Arctic Council and International Union for Circumpolar Health (IUCH) human health research activities. The human health legacy of the IPY will be increased visibility of the human health concerns of Arctic communities, revitalization of cooperative Arctic human health research focused on those concerns, the development of health policies based on research findings, and the subsequent implementation of appropriate interventions, prevention and control measures at the community level.

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 randomized trial of triple therapy for pediatric Helicobacter pylori infection and risk factors for treatment failure in a population with a high prevalence of infection.

BACKGROUND: Few trials of treatment for Helicobacter pylori infection have been conducted in high-prevalence or pediatric populations, and risk factors for treatment failure are poorly understood. METHODS: As part of a study evaluating the effect of H. pylori therapy on iron deficiency, we conducted a household-randomized, open-label treatment trial involving children aged 7-11 years in 10 villages in western Alaska. We screened 690 children, of whom 219 with iron deficiency and H. pylori infection (determined on the basis of positive results of the 13C urea breath test) were enrolled in the treatment phase of the study. These 219 children received treatment with iron sulfate alone (the control group) or with iron sulfate combined with a 2-week course of lansoprazole, clarithromycin, and amoxicillin (the intervention group). Children in the intervention group who were allergic to amoxicillin or macrolides received metronidazole. Children in the intervention group who did not respond to treatment were re-treated with a 2-week course of metronidazole-based quadruple therapy. RESULTS: Two months after initiating therapy, 34% of 104 children in the intervention group and 0.90% of 111 children in the control group tested negative for H. pylori. Among children in the intervention group, risk factors for treatment failure were lack of metronidazole (adjusted odds ratio [aOR], 145), fewer treatment doses (aOR, 0.74), larger household population (aOR, 1.5), and lower body mass index (aOR, 0.69). These 4 variables predicted most of the variation in H. pylori infection status. Among 50 children who were re-treated, 84% tested negative for H. pylori at the 8-month follow-up visit, including those with poor treatment compliance. CONCLUSIONS: Among disadvantaged populations with a high prevalence of H. pylori infection, the response to standard treatment regimens may be low. Treatment compliance, household crowding, and re-treatment may influence treatment success. Metronidazole may be appropriate first-line therapy.

Persistence of antibody to hepatitis B and protection from disease among Alaska natives immunized at birth.

BACKGROUND: Alaska Native (AN) children were at high risk of acquiring hepatitis B virus (HBV) infection before vaccination began in 1983. We evaluated the long-term protection from hepatitis B (HB) vaccination among AN children immunized when infants. METHODS: During 1984-1995, we recruited a convenience sample of AN children who had received a three dose series of HB vaccine starting at birth and had serum antibody to hepatitis B (anti-HBs) concentrations of >/= 10 mIU/mL at 7-26 months of age. We evaluated anti-HBs concentrations and the presence of anti-HBc in participants' sera every other year up to age 16 years. Anti-HB core antigen (anti-HBc)-positive specimens were tested for hepatitis B surface antigen and for HBV DNA. RESULTS: We followed 334 children for 3151 person-years (median, 10 years per child) with 1610 specimens collected. Anti-HBs concentrations dropped rapidly among all participants. Among children 2, 5 and 10 years of age, 37 of 79 (47%), 33 of 176 (19%) and 8 of 95 (8%), respectively, had anti-HBs concentrations of >/= 10 mIU/mL. Receipt of recombinant vaccine was significantly associated with a more rapid antibody decline (P < 0.001). Six (1.8%) children acquired anti-HBc, 3 of whom had definite breakthrough infections (at least 2 consecutive anti-HBc-positive specimens or at least 1 anti-HBc-positive specimen and HBV DNA detection by PCR). None of these children had detectable hepatitis B surface antigen, and none had symptoms of hepatitis. CONCLUSIONS: Anti-HBs concentrations declined over time among AN infants successfully immunized with HB vaccine starting at birth. Transient anti-HBc appeared in a small percentage of children; however, none developed clinical signs of hepatitis or chronic HBV infection.

The relationship among previous antimicrobial use, antimicrobial resistance, and treatment outcomes for Helicobacter pylori infections.

BACKGROUND: The relationship between previous antimicrobial treatments and infection with drug-resistant Helicobacter pylori is unknown. OBJECTIVES: To determine whether previous use of antimicrobial agents predicts subsequent antibiotic resistance of H. pylori and whether resistance affects treatment outcome. DESIGN: Retrospective cohort analysis of adults recruited sequentially from a clinical practice. SETTING: A referral hospital in Anchorage, Alaska. PATIENTS: 125 adults infected with H. pylori. MEASUREMENTS: Medical records were reviewed for antimicrobial agents prescribed in the 10 years before diagnosis with H. pylori infection. Antimicrobial susceptibility of H. pylori isolates obtained from endoscopic gastric biopsy was determined by using agar dilution. Cure was determined by using the urea breath test 2 months after antimicrobial treatment. RESULTS: Among the 125 patients, 37 (30%) were found to have H. pylori isolates resistant to clarithromycin and 83 (66%) were found to have H. pylori isolates resistant to metronidazole. Resistance to clarithromycin was associated with previous use of any macrolide antibiotic (P < 0.001), and resistance to metronidazole was associated with previous use of metronidazole (P < 0.001). The odds of isolates being resistant to clarithromycin increased in relation to the number of courses of macrolides received (P < 0.001). Among 53 persons treated with clarithromycin-based regimens, treatment failed in 77% of those carrying clarithromycin-resistant H. pylori (10 of 13) and 13% of those with clarithromycin-susceptible strains (5 of 40) (relative risk, 6.2 [95% CI, 1.9 to 37.1]; P < 0.001). CONCLUSIONS: Previous use of macrolides and metronidazole is associated with H. pylori resistant to these antimicrobial agents. Clarithromycin resistance is associated with a greater risk for failure with clarithromycin-based treatments.

Potential impacts of climate change on infectious diseases in the Arctic.

Climate change could cause changes in the incidence of infectious diseases in Arctic regions. Higher ambient temperatures in the Arctic may result in an increase in some temperature sensitive foodborne diseases such as gastroenteritis, paralytic shellfish poisoning and botulism. An increase in mean temperature may also influence the incidence of infectious diseases of animals that are spread to humans (zoonoses) by changing the population and range of animal hosts and insect vectors. An increase in flooding events may result in outbreaks of waterborne infection, such as Giardia lamblia or Cryptospordium parvum. A change in rodent and fox populations may result in an increase in rabies or echinococcosis. Temperature and humidity influence the distribution and density of many arthropod vectors which in turn may influence the incidence and northern range of vectorborne diseases such as West Nile virus. Recommendations include: the strenghtening of public health systems, disease surveillance coordinated with climate monitoring, and research into the detection, prevention, control and treatment of temperature-sensitive infectious diseases.

Climate Change in the North American Arctic: A One Health Perspective.

Climate change is expected to increase the prevalence of acute and chronic diseases among human and animal populations within the Arctic and subarctic latitudes of North America. Warmer temperatures are expected to increase disease risks from food-borne pathogens, water-borne diseases, and vector-borne zoonoses in human and animal populations of Arctic landscapes. Existing high levels of mercury and persistent organic pollutant chemicals circulating within terrestrial and aquatic ecosystems in Arctic latitudes are a major concern for the reproductive health of humans and other mammals, and climate warming will accelerate the mobilization and biological amplification of toxic environmental contaminants. The adverse health impacts of Arctic warming will be especially important for wildlife populations and indigenous peoples dependent upon subsistence food resources from wild plants and animals. Additional research is needed to identify and monitor changes in the prevalence of zoonotic pathogens in humans, domestic dogs, and wildlife species of critical subsistence, cultural, and economic importance to Arctic peoples. The long-term effects of climate warming in the Arctic cannot be adequately predicted or mitigated without a comprehensive understanding of the interactive and synergistic effects between environmental contaminants and pathogens in the health of wildlife and human communities in Arctic ecosystems. The complexity and magnitude of the documented impacts of climate change on Arctic ecosystems, and the intimacy of connections between their human and wildlife communities, makes this region an appropriate area for development of One Health approaches to identify and mitigate the effects of climate warming at the community, ecosystem, and landscape scales.

Changes in antibiotic-prescribing practices and carriage of penicillin-resistant Streptococcus pneumoniae: A controlled intervention trial in rural Alaska.

From 1998 to 2000, 13 rural Alaskan villages (population, 3326) were surveyed annually by nasopharyngeal cultures for Streptococcus pneumoniae carriage. Data regarding antibiotic use for the entire population was abstracted from clinic records. In 1999, education of medical providers and the community about appropriate antibiotic use began in 4 villages; this program was expanded to include all villages in 2000. Antibiotic courses per person decreased by 31% in the initial intervention villages and by 35% in the remaining villages after education (P<.01 for each). Samples were obtained for culture from a mean of 31% of the population each year; 31% carried pneumococcus. No sustained decrease in carriage of penicillin-nonsusceptible strains was observed. When linear regression was used, serotype accounted for 81% of the variance in pneumococcal minimum inhibitory concentrations after the intervention, compared with 7% for antibiotic use. This suggests that reducing the carriage of serotypes associated with antibiotic resistance by use of pneumococcal conjugate vaccines may have a greater short-term impact than does decreasing antibiotic use.

Invasive pneumococcal disease among Navajo adults, 1989-1998.

Compared with white and black persons in the United States, some Native American groups are at increased risk for invasive pneumococcal disease (IPD). To characterize the epidemiology of IPD among Navajo adults, we conducted active surveillance for IPD on the Navajo Nation and reviewed medical records of patients with IPD. For 1997-1998, the annual incidence (cases per 100,000 persons) was 56 for Navajos aged 18-64 years and 190 for Navajos aged > or =65 years. The corresponding rates were 10 and 57 for white and 44 and 82 for black persons in the United States. The case-fatality rate was 14%. Eighty percent of cases were caused by serotypes included in the 23-valent pneumococcal polysaccharide vaccine. Navajo adults have rates of IPD that are 3-5-fold higher than those of the general US population. Additional research is needed to understand the reasons for this elevated risk and to develop prevention strategies.

Duration of hepatitis B immunity in low risk children receiving hepatitis B vaccinations from birth.

BACKGROUND: The duration of protection after hepatitis B vaccination of infants is unknown. METHODS: We determined antibody to hepatitis B surface antigen (anti-HBs) at 4-13 years of age in 363 low risk children who had been vaccinated starting at birth with hepatitis B vaccine. Those with nonprotective titers (<10 mIU/mL) received a booster dose. We similarly followed 16 children of hepatitis B surface antigen (HBsAg)-positive mothers. RESULTS: Of low risk infants receiving a plasma-derived vaccine, 41% (42 of 102) of those whose primary response was unknown and 24% (4 of 17) who had initially responded retained protective titers (> or = 10 mIU/mL) of anti-HBs at 9 and 13 years, respectively. Of those who did not have protective antibody titers, 61% (33 of 54) and 67% (8 of 12), respectively, responded to a booster dose. In children of HBsAg-positive mothers, 31% retained protective anti-HBs at 12 years, and 90% (9 of 10) with nonprotective titers responded to a booster. In low risk children initially receiving a recombinant vaccine, 12.5% (26 of 208) and none (0 of 36) retained protective anti-HBs titers at 5 and 7 years of age, respectively. Of those who did not have protective titers, 90% (120 of 134) and 91% (32 of 35), respectively, responded to a booster. CONCLUSIONS: Anti-HBs disappeared by 5 years of age in most children who were vaccinated with hepatitis B vaccine from birth. Although most children showed immunologic memory, one-third failed to demonstrate an anamnestic response to a booster dose. Additional long term studies of low risk infants are needed to determine duration of protection and the necessity for or timing of booster doses.