Impact of Haemophilus influenzae Type b conjugate vaccine in Mongolia: prospective population-based surveillance, 2002-2010.

OBJECTIVES: Bacterial meningitis is associated with high mortality and long-term complications. This study assessed the impact of Haemophilus influenzae type b (Hib) conjugate vaccine on childhood bacterial meningitis in Ulaanbaatar, Mongolia. STUDY DESIGN: Prospective, active, population-based surveillance for suspected meningitis in children aged 2-59 months was conducted (February 2002-January 2011) in 6 hospitals. Clinical data, blood, and cerebrospinal fluid were collected. The impact of Hib conjugate vaccine was assessed by comparing Hib and all cause meningitis data in the 3 years preceding pentavalent conjugate vaccine implementation (2002-2004) with 3 years postimplementation (2008-2010). RESULTS: Five hundred eleven cases of suspected meningitis were identified from 2002-2011. Pentavalent conjugate vaccine coverage in December 2005 in Ulaanbaatar city was 97%. The proportion of suspected cases confirmed as Hib meningitis decreased from 25% (50/201) in the prevaccination era to 2% (4/193) in the postvaccination era (P < .0001). The annual incidence of Hib decreased from 28 cases per 100,000 children in 2002-2005 to 2 per 100,000 in 2008-2010 (P < .0001). CONCLUSIONS: This article demonstrates the marked impact of Hib conjugate vaccine introduction on meningitis in Mongolia. It is important to sustain this surveillance system to monitor the long-term impact of Hib conjugate vaccine, as well as other interventions such as pneumococcal and meningococcal vaccines.

Tracking maternal mortality declines in Mongolia between 1992 and 2007: the importance of collaboration.

OBJECTIVE: To describe the declining trend in maternal mortality observed in Mongolia from 1992 to 2007 and its acceleration after 2001 following implementation of the Maternal Mortality Reduction Strategy by the Ministry of Health and other partners. METHODS: We performed a descriptive analysis of maternal mortality data collected through Mongolia's vital registration system and provided by the Mongolian Ministry of Health. The observed declining mortality trend was analysed for statistical significance using simple linear regression. We present the maternal mortality ratios from 1992 to 2007 by year and review the basic components of Mongolia's Maternal Mortality Reduction Strategy for 2001-2004 and 2005-2010. FINDINGS: Mongolia achieved a statistically significant annual decrease in its maternal mortality ratio of almost 10 deaths per 100 000 live births over the period 1992-2007. From 2001 to 2007, the maternal mortality ratio in Mongolia decreased approximately 47%, from 169 to 89.6 deaths per 100 000 live births. CONCLUSION: Disparities in maternal mortality represent one of the major persisting health inequities between low- and high-resource countries. Nonetheless, important reductions in low-resource settings are possible through collaborative strategies based on a horizontal approach and the coordinated involvement of key partners, including health ministries, national and international agencies and donors, health-care professionals, the media, nongovernmental organizations and the general public.

Childhood bacterial meningitis in Ulaanbaatar, Mongolia, 2002-2004.

BACKGROUND: Childhood bacterial meningitis is severe and largely preventable by vaccination. Few data on childhood bacterial meningitis in Northeast and Central Asia exist. Our aim was to determine the incidence and etiology of childhood bacterial meningitis in Ulaanbaatar, Mongolia. METHODS: We conducted prospective, population-based, active hospital surveillance for clinical meningitis in children 2 months to 5 years of age. Clinical data, blood, and cerebrospinal fluid were collected according to a standard protocol. Laboratory testing was performed at 2 reference laboratories in Ulaanbaatar. RESULTS: From February 2002 to January 2005, 201 suspected meningitis cases were identified in residents of Ulaanbaatar. The average annual incidence rate for confirmed and probable bacterial meningitis (cases with culture-negative, purulent cerebrospinal fluid) was 68 cases per 100,000 children aged 2 months to 5 years. The average annual incidence rate of confirmed cases was 28 cases per 100,000 children for Haemophilus influenzae type b meningitis, 11 cases per 100,000 children for pneumococcal meningitis, and 13 cases per 100,000 children for meningococcal meningitis. Adjusting for cases without complete cerebrospinal fluid information and culture-negative, probable bacterial cases, the estimated incidence rate was 40 cases per 100,000 children for H. influenzae type b meningitis, 15 cases per 100,000 children for pneumococcal meningitis, and 17 cases per 100,000 children for meningococcal meningitis. CONCLUSION: H. influenzae type b is the leading cause of childhood bacterial meningitis in Ulaanbaatar, and the incidence rate is higher than that reported from other Asian countries. These data supported the recent introduction of H. influenzae type b conjugate vaccine in Mongolia. Ongoing surveillance will monitor the impact of the vaccine.

Prevalence and genotype distribution of hepatitis C virus among apparently healthy individuals in Mongolia: a population-based nationwide study.

BACKGROUND AND AIMS: Hepatitis C virus (HCV) is one of the major causes of liver cirrhosis and hepatocellular carcinoma (HCC) in Mongolia. However, there are no data concerning nationwide prevalence of HCV infection in Mongolia. We intended to investigate the population-based prevalence of HCV infection and genotype distribution among 1512 apparently healthy individuals in this country. METHODS: Between April 2003 and December 2005, sera from 1512 residents of Ulaanbaatar and 12 provinces were collected by two-stage cluster random sampling, and anti-HCV was tested. Anti-HCV-positive samples were tested for HCV RNA by reverse transcription polymerase chain reaction, and HCV genotype was determined. RESULTS: The mean age of the subjects was 46.2+/-17.8 years, and 812 (53.7%) were male. Overall, the prevalence of anti-HCV was 15.6% (236/1512) and HCV RNA was detected in 167 subjects (11.0%), with the most common genotype being 1b (165/167, 98.8%). When the HCV RNA-positive subjects were categorized by decade of age, the prevalence in each age group was as follows: 2.5% in subjects /=61 years of age. The seroprevalence of anti-HCV in a risk group, nurses, was not significantly different from the general population in each decade of age (P>0.05). CONCLUSIONS: Approximately 11.0% of apparently healthy population had detectable HCV RNA in Mongolia, and the predominant genotype of HCV was 1b. Preventive and therapeutic strategies for chronic hepatitis C are urgently warranted in this HCV-endemic area.

Measles outbreak after a post-honeymoon period in Mongolia, 2001.

In spite of the routine 2-dose vaccination and three recent supplemental immunizations, Mongolia experienced a measles outbreak in 2001, the largest epidemic in the country since 1984. The majority of cases were reported in the capital city, and the disease incidence was higher in infants and adolescents than in other age groups. Young adults who received the immunization only once may have low immunity, and may be exposed to the virus most frequently. Immunization strategies such as the age range that is targeted for vaccination and the interval between supplemental immunizations should be based on reasonable epidemiological observations.

Impact of the universal hepatitis B immunization program in Mongolia: achievements and challenges.

BACKGROUND: The impact of the universal infant hepatitis B (HB) immunization program initiated in 1991 in Mongolia is still unclear. METHODS: A nationwide school-based cross-sectional serosurvey was conducted in 2004, with stratified, multistage, random cluster sampling from all public elementary schools (n=593) in Mongolia. All children were tested for serological markers of hepatitis B virus (HBV). RESULTS: Serology results were available for 1,145 children (592 boys and 553 girls) aged 7-12 years (survey response rate: 93%). Immunization card was available for 702 (61.3%) children. The coverage of complete HB vaccination was 60.1% and it was increased by birth cohort from 44% to 76%. Significantly higher proportion of children in Metropolitan cities (75.2%) was completely vaccinated with HB compared to those in Province centers (55.7%) and rural areas (59.1%). HBV infection occurred in 5.9%, 13.2%, and 20.8% of complete vaccinees living in Metropolitan, Province centers, and rural areas, respectively; of whom 1.2%, 2.9%, and 8.6% were HB surface antigen (HBsAg) carriers, respectively. Only 17.0% of the children had protective anti-HBs which decreased from 31.1% to 16.3% among 7 to 12-year-olds indicating its decay with time. CONCLUSIONS: Prevalence of HBV infection and carriage among young generation meaningfully declined compared with those of previous studies in Mongolia. The coverage of birth dose and complete HB vaccination was significantly low in Province centers and rural areas which should be taken into consideration.

Administration of hepatitis B vaccine in winter as a significant predictor of the poor effectiveness of vaccination in rural Mongolia: evidence from a nationwide survey.

BACKGROUND: Universal hepatitis B (HB) immunisation is the most effective means for prevention of hepatitis B virus (HBV) infection worldwide. Maintaining the vaccine cold chain is an essential part of a successful immunisation programme. Our recent nationwide survey in Mongolia has observed significant urban-rural differences in the prevalence of HBV infection among vaccinated cohorts. OBJECTIVE: To examine whether the administration of HB vaccine in winter contributes to these residential discrepancies on the effectiveness of vaccination. DESIGN AND SETTING: In 2004, a nationwide serosurvey was carried out covering both urban and rural areas of Mongolia. Sampling was multistage, with random probability from all public schools in the country. PARTICIPANTS: A random sample of 1145 children (51.7% boys; aged 7-12 years), representative of Mongolian elementary school children. RESULTS: Multivariate logistic regression analysis identified that total (past and current) HBV infection (OR 2.31, 95% CI 1.20 to 4.42; p = 0.012) was independently associated with the administration of all HB vaccines in winter. An increased OR for current HBV infection was also observed (OR 2.58, 95% CI 0.87 to 7.68; p = 0.089), but without significance. Interestingly, after stratifying by residence, the association between winter vaccination and total HBV infection was evident for rural (p = 0.008) but not for urban areas (p = 0.294). The frequency of vaccine-induced immunity was significantly (p = 0.007) lower for those who received HB vaccine at birth during winter in rural areas. CONCLUSION: Administration of HB vaccine during winter is an important predictor of the low effectiveness of vaccination in rural Mongolia. To improve the effectiveness of HB vaccination in remote areas, cold chain control should be addressed with particular attention to the winter season.

Seroepidemiology of hepatitis B virus infection among children in Mongolia: results of a nationwide survey.

BACKGROUND: Because Mongolia is one of the highly endemic countries for hepatitis B virus (HBV) infection in the world, hepatitis B (HB) vaccine was introduced into the National Expanded Program on Immunization in 1991. However, relatively few data are available concerning HBV infection among children born after the start of the program, so far. The aim of the present paper was to describe the seroepidemiology of HBV infection among primary school children using representative national data. METHODS: In 2004, a nationwide school-based cross-sectional serosurvey was carried out throughout Mongolia, covering both urban and rural areas. Serum samples were tested for hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc) and hepatitis B e antigen (HBeAg) as well as for liver enzymes. RESULTS: A total of 1145 children aged 7-12 years were studied, which represents nearly 2% of the second grade population of elementary schools in Mongolia. The overall prevalence of HBsAg and anti-HBc was 5.2% (95% confidence interval [CI]: 3.9-6.5%) and 15.6% (95%CI: 13.5-17.7%), respectively. Among HBsAg-positive children 67.8% (95%CI: 55.9-79.7%) were also positive for HBeAg. The prevalence of chronic HBV infection increased by age and was significantly higher among children from rural areas compared to those from urban areas (7.7% vs 3.0%; P < 0.001). In the multivariate logistic regression analysis, rural residence (odds ratio [OR]: 2.57; 95%CI: 1.45-4.58), male sex (OR: 1.9; 95%CI: 1.08-3.26) and age (OR: 1.5; 95%CI: 1.10-2.05) were independent demographic predictors for chronic HBV infection. CONCLUSIONS: The prevalence of chronic HBV infection has been decreasing in the Mongolian young generation, most likely due to infant HB vaccination. However, significant rural-urban differences in the prevalence of HBV infection were found that demand further investigation to estimate the potential causes.

Hepatitis delta virus infection in mongolia: analyses of geographic distribution, risk factors, and disease severity.

The prevalence and risk factors for hepatitis delta virus (HDV) infection among Mongolian school children were assessed by detecting the antibody against HDV and HDV RNA, and through structured interviews. The study subjects consisted of 181 children with the past or ongoing hepatitis B virus infection who were investigated during the nationwide serosurvey conducted in 2004. The prevalence of antibody to HDV was 6.1%, with the proportion of 13.6% among hepatitis B surface antigen (HBsAg)-positive subjects, all of whom had HDV RNA. Multivariate logistic regression analyses showed that injections (> 11 times) (odds ratio [OR] = 8.31, 95% confidence interval [CI] = 1.28-54.07) and blood sampling (> 3 times) (OR = 5.34, 95% CI = 1.12-25.53) in health care settings, hospitalization (> 3 times) (OR = 6.20, 95% CI = 1.18-32.71), and cohabitating with patients with chronic hepatitis (OR = 4.57, 95% CI = 1.26-16.55) predicted the seropositivity for antibody to HDV. These results suggest that parenteral exposures in health care settings and household transmission are the main routes of HDV transmission among Mongolian children.

Prevalence and risk factors for hepatitis C virus infection in Mongolian children: Findings from a nationwide survey.

Although the hepatitis C virus (HCV) infection is one of the major causes of chronic hepatitis and hepatocellular carcinoma (HCC) in Mongolia, its prevalence among children and routes of transmission are largely unknown. The aim of the study was to determine the prevalence of anti-HCV antibodies and the possible risk factors for transmission among school children using representative national data. A nationwide cross-sectional survey among elementary school children was conducted in four main geographical regions and the metropolitan area of Mongolia, through multistage, stratified, random cluster sampling. Serum samples from 1,145 children (response rate, 93%; 592 boys and 553 girls; age range, 7-12 years), which represented nearly 2% of the second grade population in Mongolia, were tested for HCV antibodies with a third-generation immunoradiometric assay (IRMA). Positive samples were further evaluated by a third-generation immunoblot assay (RIBA). A standardized questionnaire concerning the socio-demographic characteristics and potential risk factors was used. Overall, seven subjects were confirmed to be anti-HCV seropositive, giving a prevalence of 0.6% (95% CI: 0.15-1.0%). The prevalence of anti-HCV increased with age. In the multivariate logistic regression analysis, adjusted for age, sex, and residence, the history of dental manipulation (odds ratio [OR] = 15.4; 95% CI: 1.4-164.8) and surgery (OR = 8.3; 95% CI: 1.5-45.6) were associated independently with the presence of anti-HCV. These findings suggest that contaminated equipment used in the dental and surgical manipulations probably played a predominant role in HCV transmission among Mongolian children. Strict guidelines on disinfection and sterilization procedures of medical instruments have to be introduced and should be followed to improve the control of HCV infection in Mongolia.