Hepatitis B seroprevalence in Thailand: 12 years after hepatitis B vaccine integration into the national expanded programme on immunization

Molecular epidemiological study of hepatitis B virus among migrant workers from Cambodia, Laos, and Myanmar to Thailand

Although hepatitis B virus (HBV) infection is endemic in Southeast Asia, molecular epidemiological data on HBV circulating in some countries are limited. The aims of this study were to evaluate the seroprevalence of HBV and its genetic variability among migrant workers from Cambodia, Laos, and Myanmar in Thailand. Sera collected from 1,119 Cambodian, 787 Laotian, and 1,103 Myanmarese workers were tested for HBsAg. HBV DNA was amplified and the pre-S/S region was sequenced for genotyping and genetic mutation analysis. HBsAg was detected in 282 (9.4%). The prevalence of HBsAg among migrant workers from Cambodia, Laos, and Myanmar was 10.8%, 6.9%, and 9.7%, respectively. Of 224 subjects positive for HBV DNA, 86% were classified as genotype C (99% were sub-genotype C1) and 11.6% were genotype B (30.8%, 34.6%, and 30.8% were sub-genotypes B2, B3, and B4, respectively). Various point mutations in the "a" determinant region were detected in approximately 18% of these samples, of which Ile126Ser/Asn was the most frequent variant. Sequencing analysis showed that 19.1% of samples had pre-S mutations, with pre-S2 deletion as the most common mutant (7.7%) followed by pre-S2 start codon mutation (3.8%) and both pre-S2 deletion and start codon mutation (3.3%). High prevalence of HBV infection (approximately 7-11%) was found among migrant workers from Cambodia, Laos, and Myanmar, which may reflect the current seroprevalence in their respective countries. The data also demonstrated that HBV sub-genotype C1 was the predominant strain and various mutations of HBV occurring naturally were not uncommon among these populations.

Serologic and molecular characteristics of hepatitis B virus among school children in East Java, Indonesia

Universal childhood hepatitis B vaccination was introduced in Indonesia in 1997; by 2008, coverage was estimated to be 78%. This study aimed to investigate the serologic status and virologic characteristics of hepatitis B virus (HBV) among the children in East Java. A total of 229 healthy children born during 1994-1999 were enrolled in this study. Overall, 3.1% were positive for hepatitis B surface antigen (HBsAg) and 23.6% were positive for antibody to HBsAg (anti-HBs). HBV DNA was detected in 5 of 222 HBsAg-negative carriers, which were suggested to be cases of occult HBV infection. A single amino substitution (T126I) in the S region was frequently found. HBV infection remains endemic, and the prevalence of anti-HBs remains insufficient among children in East Java, Indonesia.

Implementing a birth dose of hepatitis B vaccine for home deliveries in Africa--too soon?

Despite the recommendation of the World Health Organization (WHO) to provide the first hepatitis B vaccine dose at birth (within 24h), there are epidemiological, economic and logistical reasons why this may not be the best approach for home births in Africa. The WHO policy presupposes that the epidemiology of hepatitis B infection in Africa is similar to the rest of the world and that the organizational, infrastructural and financial support is adequate. While babies born in health facilities may be relatively easy to immunize at birth, health systems and infrastructures in many resource-poor countries in Africa would be severely challenged, if required to reach home deliveries within 24h of birth.

A vesicular stomatitis virus-based hepatitis B virus vaccine vector provides protection against challenge in a single dose

As one of the world's most common infectious diseases, hepatitis B virus (HBV) is a serious worldwide public health problem, with HBV-associated liver disease accounting for more than half a million deaths each year. Although there is an effective prophylactic vaccine currently available to prevent infection, it has a number of characteristics that are suboptimal: multiple doses are needed to induce long-lasting immunity, immunity declines over time, it does not elicit protection in some individuals, and it is not effective therapeutically. We produced a recombinant vesicular stomatitis virus (VSV)-based vaccine vector expressing the HBV middle envelope surface protein (MS) and found that this vector was able to efficiently generate a strong HBs-specific antibody response following a single immunization in mice. A single immunization with the VSV-MS vector also induced robust CD8 T-cell activation. The CD8 T-cell response was greater in magnitude and broader in specificity than the response generated by a vaccinia virus-based vaccine vector or by recombinant protein immunization. Furthermore, a single VSV-MS immunization provided protection against virus challenge in mice. Given the similar antibody titers and superior T-cell responses elicited from a single immunization, a VSV-based HBV vaccine may have advantages over the current recombinant protein vaccine.

Web interface-supported transmission risk assessment and cost-effectiveness analysis of postdonation screening: a global model applied to Ghana, Thailand, and the Netherlands

BACKGROUND

The goal of our research was to actively involve decision makers in the economic assessment of screening strategies in their region. This study attempted to accomplish this by providing an easy-to-use Web interface at http://www.bloodsafety.info that allows decision makers to adapt this model to local conditions.

STUDY DESIGN AND METHODS

The cost-effectiveness was compared of 1) adding antigen screening to antibody screening for hepatitis C virus (HCV) and human immunodeficiency virus (HIV); 2) adding nucleic acid amplification testing (NAT) on hepatitis B virus (HBV), HCV, and HIV in minipool (pool of 6 [MP6] and 24 [MP24]) to antibody screening and hepatitis B surface antigen (HBsAg) screening; and 3) individual-donation NAT on HBV, HCV, and HIV to antibody screening and HBsAg screening for Ghana, Thailand, and the Netherlands.

RESULTS

The combination of HCV antibody-antigen combination (combo) and HIV combo added to antibody screening in Ghana and Thailand was cost-effective according to the WHO criteria. MP24-NAT screening in Ghana was also cost-effective. MP24-NAT on HBV, HCV, and HIV was not cost-effective compared to the other screening strategies evaluated for the Netherlands. Large regional differences in cost-effectiveness were found for Thailand.

CONCLUSION

The young transfusion recipient population of Ghana in combination with a high risk of viral transmission yields better cost-effectiveness for additional tests. The advanced age of the transfused population of the Netherlands and a small risk of viral transmission gives poor cost-effectiveness for more sensitive screening techniques. It was demonstrated that a global health economic model combined with a Web interface can provide easy access to risk assessment and cost-effectiveness analysis.

Persistence of antibodies and immune memory to hepatitis B vaccine 20 years after infant vaccination in Thailand

Booster vaccination against hepatitis B (HBV) is not currently recommended, although debate continues on the duration of protection after priming. We assessed antibody persistence and immune memory to hepatitis B 20 years after priming with a recombinant HBV-vaccine during infancy. Infants were vaccinated at birth, 1, 2 and 12 months of age. A subset received a booster dose at Year 5. Antibody persistence was measured approximately yearly until Year 20. Immune memory was assessed by administration of HBV booster dose. At Year 20, anti-HBs seroprotection rates and GMCs tended to be higher in Year 5 boosted than unboosted recipients (83.9% versus 60.5%). After the Year 20 booster dose, anti-HBs anamnestic responses were within the same range 95.8% of subjects in both groups. Primary and booster vaccination with HBV-vaccine in infants induces sustained seroprotection and immune memory against hepatitis B for up to 20 years. Higher persisting seroprotection rates in subjects boosted at Year 5 did not translate into apparent differences in immune memory in a high endemic country.

Control of hepatocellular carcinoma through hepatitis B vaccination in areas of high endemicity: perspectives for global liver cancer prevention

There are approximately 360 millions chronic carriers of Hepatitis B virus worldwide. Patterns of HB carriage are variable from one region to the other. Regions with rates of carriage over 8% are commonly considered as "high endemicity" regions. HB carriers have a very significant lifetime risk of developing chronic liver diseases such as cirrhosis and/or liver cancer (hepatocellular carcinoma, HCC). An efficient HB vaccine is available since the early eighties and has been used since for universal infant vaccination in regions of high endemicity. Observations from Taiwan, where universal infant vaccination was introduced from 1984, show a remarkable, long-lasting protection against carriage and reduction of HCC rates in adolescent and young adults born after the initiation of the programme. Two population-based trials have been set up in the mid-eighties to evaluate lifelong protective effects of infant HB vaccine against liver cancer, in The Gambia (West Africa) and in the area of Qidong, China. In other high-endemicity regions of Asia and Africa, universal infants vaccination has consistently showed a long-lasting high protection against chronic carriage and this is expected to lead to a dramatic decrease of chronic liver disease and liver cancer within the next decades. Here we briefly review the lessons of vaccination programmes and trials in high-endemicity regions, based on data gathered during 15-20years of implementation.

Increased risk of developing chronic HBV infection in infants born to chronically HBV infected mothers as a result of delayed second dose of hepatitis B vaccination

This two-stage study (cross-sectional and case-control) assessed the effects of delayed second dose HB vaccination on the risk of developing chronic HBV infection in infants born to chronically HBV infected mothers. 521 infants enrolled received the first vaccination by the end of the day after birth, without HBIG. 15 of these infants were chronically HBV infected. In the case-control comparison, controlling for HBeAg in the mother, the risk of an infant becoming chronically infected was 3.74 times (95% CI=0.97-14.39) higher if the interval between the first and the second doses exceeded 10 weeks. This finding suggests it is important that immunization programs ensure timely second dose vaccination to infants born to mothers with chronic HBV infection. Nevertheless, due to the small sample size, these findings should be verified by larger studies.

Hepatitis B immunity in adolescents and necessity for boost vaccination: 23 years after nationwide hepatitis B virus vaccination program in Taiwan

The first universal hepatitis B vaccination program for newborns in the world was launched in Taiwan in July 1984. Most studies on the effectiveness of hepatitis B vaccination focused on the seroprevalence of HBs Ag among children under 14 years old. Only few studies focused on the seropositivity of anti-HBs among adolescents aged 15-18 years old. The present study aimed to evaluate the impact of the nationwide hepatitis B vaccination program on the immunity to HBV infection and the necessity of boost among adolescents. In this study including eight annual seroprevalence surveys from 2000 to 2007, 2342 college entrants (1589 15-year-olds in group I and 753 18-year-olds in group II) and 1851 university freshmen (18-year-olds in group III) participated. Subjects identified anti-HBs, HBs Ag and anti-HBc negative were given boost three doses of HBV vaccine. The HBs Ag seroprevalence was 11.6%, 3.5% and 1.0% for participants who were born before 1984, 1984-1986 and after 1986. The anti-HBs-seropositive rates were significantly higher in group II (83.1%) than in group I (53.0%) and group III (53.5%). All 572 participants who were seronegative for anti-HBs, HBs Ag and anti-HBc became anti-HBs-seropositive after catch-up vaccination. It is concluded that the anti-HBs-seropositive rate decreased to 50% in 15 years after vaccination, and boost vaccination was 100% effective. The necessity and age for boost among anti-HBs negative adolescents and the timing of the first immunization should be further evaluated.

Chronic hepatitis B in Asian women of childbearing age

Hepatitis B virus (HBV) infection is a serious clinical problem affecting approximately 2 billion people worldwide. An estimated 350 million live with chronic hepatitis B (CHB) infection and are at an increased risk for serious liver sequelae and death from acute or chronic consequences of CHB infection. Individuals with CHB have a 20-30% risk of early death from complications, including liver cirrhosis and hepatocellular carcinoma. In the Asia-Pacific region, half of the CHB burden results from vertical or mother-to-child transmission, with early childhood horizontal transmission accounting for the remaining half. Screening and vaccination are key factors in the successful prevention and control of HBV infection. Over the last 20 years, the implementation of screening programs and universal HBV vaccination for all individuals born in endemic areas have reduced the prevalence of HBV infection and HBV-related liver diseases among individuals younger than 30 years. Women of childbearing age are key stakeholders in preventing HBV infection and, as such, play a critical role in reducing the vertical and horizontal transmission of HBV. Further efforts are needed to implement screening and educational programs for women of childbearing age, particularly those with CHB, to prevent the transmission of HBV to newborns, spouses, other household members, and sexual partners. In addition, healthcare workers need to learn how to avoid iatrogenic transmission in the healthcare setting. This article reviews these issues and highlights areas in which their engagement with public health efforts serves to improve quality of life and society as a whole.

Hepatitis antibody profile of Royal Thai Army nursing students

We report on a viral hepatitis serosurvey done on 381 nursing students in Bangkok; 360 (94%) were female. The mean age was 20 (+/-3.6) years (range 16-41 years); 143, 92, 86 and 59 students came from Thailand's Central, North, Northeast and South provinces, respectively. The overall prevalence of hepatitis A, B, C and E antibody in the students was 8.9%, 10.8%, 0.5% and 11.5%, respectively. The highest seroprevalence to hepatitis A was observed in cadets from the southern region of Thailand. Seroprevalence rates to hepatitis A and B were less than in other reported studies in Thailand.

High impact of migration on the prevalence of chronic hepatitis B in the Netherlands

OBJECTIVES

A representative serosurveillance study (1995) resulted in an estimate of 0.2% for the HBsAg prevalence in the Netherlands. Some risk groups, especially migrants, were not well represented in the study, which probably led to an underestimation of the true HBsAg prevalence. The aim of this study was to calculate an adjusted HBsAg prevalence estimate for the total Dutch population including these risk groups.

METHODS

According to their country of origin first-generation migrants (FGM) were classified into groups with low, intermediate and high prevalence using data from the WHO and Statistics Netherlands. The number of chronic HBsAg carriers in different age and population groups was estimated based on studies about age-specific prevalence in different countries. The number of carriers in the indigenous population was estimated using the serosurveillance study. A combination of these estimates led to an estimate of the total prevalence rate in the Netherlands.

RESULTS

Nearly 10% of the Dutch population are FGM. Of these, about 18% were born in low-endemic, 71% in middle-endemic and 11% in high-endemic countries. The overall prevalence of HBsAg in FGM is estimated to be at 3.77%. Combining these results with the results of the serosurveillance study the HBsAg prevalence in the Dutch population is estimated to be between 0.32 and 0.51%, and when including injecting drug users and mentally handicapped persons the prevalence rates are 0.36 and 0.55%, respectively.

CONCLUSION

Our results show the high importance of targeting migrants and their close contacts adequately in screening programmes, vaccination and treatment for chronic hepatitis B.

Correlates of incarceration among young methamphetamine users in Chiang Mai, Thailand

OBJECTIVES

We examined correlates of incarceration among young methamphetamine users in Chiang Mai, Thailand in 2005 to 2006.

METHODS

We conducted a cross-sectional study among 1189 young methamphetamine users. Participants were surveyed about their recent drug use, sexual behaviors, and incarceration. Biological samples were obtained to test for sexually transmitted and viral infections.

RESULTS

Twenty-two percent of participants reported ever having been incarcerated. In multivariate analysis, risk behaviors including frequent public drunkenness, starting to use illicit drugs at an early age, involvement in the drug economy, tattooing, injecting drugs, and unprotected sex were correlated with a history of incarceration. HIV, HCV, and herpes simplex virus type 2 (HSV-2) infection were also correlated with incarceration.

CONCLUSIONS

Incarcerated methamphetamine users are engaging in behaviors and being exposed to environments that put them at increased risk of infection and harmful practices. Alternatives to incarceration need to be explored for youths.

A randomized trial of combination hepatitis B therapy in HIV/HBV coinfected antiretroviral naïve individuals in Thailand

Coinfection with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) is associated with considerable liver disease morbidity and mortality. Emerging HIV epidemics in areas of high HBV endemicity such as Asia are expanding the population with HIV/HBV coinfection. Limited randomized trial data exist to support current guidelines for HBV combination therapy in HIV/HBV coinfection. The objective of this prospective randomized clinical trial was to compare the strategy of HBV monotherapy with lamivudine (LAM) or tenofovir disoproxil fumarate (TDF) versus HBV combination therapy with LAM/TDF in antiretroviral-naïve HIV/HBV-coinfected subjects in Thailand. Thirty-six HIV/HBV-coinfected subjects initiating highly active antiretroviral therapy (HAART) were randomized to either LAM (arm 1), TDF (arm 2), or LAM/TDF (arm 3) as HBV-active drugs within HAART. At week 48, time-weighted area under the curve analysis revealed that the median HBV DNA reduction from baseline was 4.07 log(10) c/mL in arm 1, 4.57 log(10) c/mL in arm 2, and 4.73 log(10) c/mL in arm 3 (P = 0.70). HBV DNA suppressed to <3 log(10) c/mL in 46% in arm 1, 92% in arm 2, and 91% in arm 3 (P = 0.013, intent-to-treat analysis). HBV-resistant changes were detected in two subjects, both in arm 1. Hepatitis B e antigen (HBeAg) loss was observed in 33% of HBeAg-positive subjects, and 8% experienced hepatitis B surface antigen loss. Hepatic flare was observed in 25% of subjects.

CONCLUSION

LAM monotherapy resulted in a greater proportion of subjects with HBV DNA >3 log(10) c/mL at week 48 and in early resistance development. This study confirms current treatment guidelines that recommend a TDF-based regimen as the treatment of choice for HIV/HBV coinfection, but does not demonstrate any advantage of HBV combination therapy in this short-term setting.

Viral hepatitis and HIV-associated tuberculosis: risk factors and TB treatment outcomes in Thailand

Background

The occurrence of tuberculosis (TB), human immunodeficiency virus (HIV), and viral hepatitis infections in the same patient poses unique clinical and public health challenges, because medications to treat TB and HIV are hepatotoxic. We conducted an observational study to evaluate risk factors for HBsAg and/or anti-HCV reactivity and to assess differences in adverse events and TB treatment outcomes among HIV-infected TB patients.

Methods

Patients were evaluated at the beginning, during, and at the end of TB treatment. Blood samples were tested for aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (BR), complete blood count, and CD4+ T lymphocyte cell count. TB treatment outcomes were assessed at the end of TB treatment according to international guidelines.

Results

Of 769 enrolled patients, 752 (98%) had serologic testing performed for viral hepatitis: 70 (9%) were reactive for HBsAg, 237 (31%) for anti-HCV, and 472 (63%) non-reactive for both markers. At the beginning of TB treatment, 18 (26%) patients with HBsAg reactivity had elevated liver function tests compared with 69 (15%) patients non-reactive to any viral marker (p = 0.02). At the end of TB treatment, 493 (64%) were successfully treated. Factors independently associated with HBsAg reactivity included being a man who had sex with men (adjusted odds ratio [AOR], 2.1; 95% confidence interval [CI], 1.1–4.3) and having low TB knowledge (AOR, 1.8; CI, 1.0–3.0). Factors most strongly associated with anti-HCV reactivity were having injection drug use history (AOR, 12.8; CI, 7.0–23.2) and living in Bangkok (AOR, 15.8; CI, 9.4–26.5). The rate of clinical hepatitis and death during TB treatment was similar in patients HBsAg reactive, anti-HCV reactive, both HBsAg and anti-HCV reactive, and non-reactive to any viral marker.

Conclusion

Among HIV-infected TB patients living in Thailand, markers of viral hepatitis infection, particularly hepatitis C virus infection, were common and strongly associated with known behavioral risk factors. Viral hepatitis infection markers were not strongly associated with death or the development of clinical hepatitis during TB treatment.

Molecular epidemiological study of hepatitis B virus in Thailand based on the analysis of pre-S and S genes

AIMS

This study was undertaken to determine the prevalence and characteristics of hepatitis B virus (HBV) genotypes, antigen subtypes, "a" determinant variants and pre-S gene mutations circulating on a large scale in Thailand.

METHODS

The sequences of the Pre-S1, Pre-S2 and S regions were determined in serum samples of 147 HBsAg and HBV DNA-positive subjects who had been enrolled from the nationwide seroepidemiological survey conducted on 6213 individuals in 2004.

RESULTS

The results showed that genotypes C, B and A accounted for 87.1%, 11.6% and 1.3%, respectively. The distribution of the HBV antigen subtypes was: adr (84.4%), adw (14.2%) and ayw (1.4%). Regarding the "a" determinant, 2/43 (4.65%) and 2/104 (1.92%) samples of vaccinated and non-vaccinated subjects, respectively, displayed mutations, all ofwhich were Thr126Asn. Sequencing analysis showed the pre-S mutations in 14 (9.5%) samples, with pre-S2 deletion as the most common mutant (4.1%) followed by pre-S2 start codon mutation (2.9%), both pre-S2 deletion and start codon mutation (2.0%), and pre-S1 deletion (0.7%). The pre-S mutations were associated with older age and higher mean serum HBsAg level.

CONCLUSION

This study demonstrated that HBV genotype/subtype C/adr and B/adw were the predominant strains circulating in Thailand. The "a" determinant variants seemed to be uncommon, and might not be attributed to vaccine-induced mutation.

Risk and predictors of mortality associated with chronic hepatitis B infection

BACKGROUND & AIMS

The study objective was to determine the risk of all-cause and cause-specific mortality as well as to examine the predictors of mortality in chronic hepatitis B infection.

METHODS

We performed a prospective cohort study of 23,820 persons (age, 30-65 y) recruited between 1991 and 1992 and followed up through 2004 from 7 townships in Taiwan. The main outcomes were all-cause and liver-related mortality rates. Mortality analyses used time-to-events methods, and survival curves were derived by the Kaplan-Meier method. Cox proportional hazard models were used to estimate multivariable-adjusted hazard ratios.

RESULTS

There were 1814 deaths during a mean follow-up period of 12.5 years (282,323.7 person-years of follow-up evaluation). Persons positive for hepatitis B surface antigen (HBsAg) had significantly (P < .01) higher adjusted hazard ratios for all causes of mortality (1.7; 95% confidence interval [CI], 1.5-1.9), liver cancer mortality (22.4; 95% CI, 15.2-32.9), and chronic liver disease and cirrhosis mortality (5.4; 95% CI, 3.5-8.4). When compared with HBsAg-negative persons, hepatitis B virus (HBV)-infected persons with HBV DNA levels less than 10(4) had a high risk of hepatocellular carcinoma mortality (4.4; 95% CI, 2.4-8.2). In HBsAg-positive persons, the mortality rate increased with cohort entry serum HBV DNA level. Liver cancer mortality ranged from 72.8 per 100,000 person-years for subjects with HBV DNA levels less than 300 copies/mL to 815.6 per 100,000 person-years for those with HBV DNA levels of 1 million copies/mL or greater. Chronic liver disease and cirrhosis deaths ranged from 9.1 to 267.4 per 100,000 person-years.

CONCLUSIONS

Chronic HBV infection is associated with significant preventable excess mortality risk. This mortality risk is correlated strongly with the level of viral replication among other factors.

Hepatitis B virus DNA in unusual serological profiles of hepatitis B surface antigen-positive sera

On the basis of a seroepidemiological survey of hepatitis B virus (HBV) infection conducted on 6208 random serum samples from four provinces of Thailand, we found 19 of 246 (7.7%) hepatitis B surface antigen (HBsAg)-positive samples with unusual serological constellations of HBV infection. Ten samples tested positive for HBsAg, anti-HBc (anti-hepatitis B core antibody), and anti-HBs (anti-hepatitis B surface antibody) markers (group I), 3 specimens were HBsAg and anti-HBs positive without detectable anti-HBc (group II), and the remaining 6 specimens showed only HBsAg (group III). In group I, 7 of 10 HBsAg-positive sera could be confirmed by HBsAg neutralization, yielding positive results for all samples. None of the group II sera were available in sufficient amounts for confirmation. In group III, five of six sera were confirmed by HBsAg neutralization, with four showing a positive reaction. HBV DNA was detected in 7 of 10 (70%) specimens in group I, in 1 of 3 (33.3%) specimens in group II, and in 3 of 6 (50%) specimens in group III. On the basis of HBsAg neutralization, HBV DNA was found in five of seven (71.4%) HBsAg-positive samples in group I and in three of four (75%) HBsAg-positive samples in group III, whereas the one confirmed HBsAg-negative sample in group III also remained negative for HBV DNA. Amino acid sequences were compared with those specifying the "a" determinant of the wild-type virus, particularly focusing on HBV-S protein variations between positions 110 and 160. Among 11 HBV DNA-positive sera, G145A was detected in 2 samples in group I, with the remaining samples identical to the wild-type virus. These unusual serological profiles may be due to the altered immune response of the host or to HBV variants.

Exposure to heat and freezing in the vaccine cold chain in Thailand

This study investigated exposure to heat and freezing of vaccines used in Thailand's National Immunization Program. Cold chain temperatures on 48 randomly selected shipment routes nationwide were monitored. Measles and hepatitis B vaccines were despatched with recording devices and subsequently tested. The study found that extremes of cold appear to be the more significant problem. Heat exposure was relatively brief and not at very high temperatures, so vaccine deterioration was unlikely, as was confirmed by measles vaccine testing. Exposure to temperatures below -0.5 degrees C was widespread, which would be expected to damage hepatitis B vaccine, but shake tests did not detect damage.