A review of the efficacy, immunogenicity and tolerability of a combined hepatitis A and B vaccine

Evaluation and Immunogenicity of Combined Liposome-Based Vaccine Candidates against Hepatitis E and B Viruses in Rhesus Monkeys

The administration of vaccines using a combination approach ensures better coverage and reduces the number of injections and cost. The present study assessed liposome-complexed DNA-corresponding proteins of hepatitis E and B viruses (HEV and HBV) as combined vaccine candidates in rhesus monkeys. The HEV and HBV components consisted of 450 bps, neutralizing the epitope/s (NE) region, and 685 bps small (S) envelope gene-corresponding proteins, respectively. Three groups (n = 2 monkeys/group) were intramuscularly immunized with a total of three doses of NE Protein (Lipo-NE-P), NE DNA + Protein (Lipo-NE-DP), and each of NE and S DNA + Protein (Lipo-NES-DP), respectively, given one month apart. All immunized monkeys were challenged with 10,000 fifty percent monkey infectious dose of homologous HEV strain. Post-immunization anti-HEV antibody levels in monkeys were 59.4 and 148.4 IU/mL (Lipo-NE-P), 177.0 and 240.8 IU/mL (Lipo-NE-DP), and 240.7 and 164.9 IU/mL (Lipo-NES-DP). Anti-HBV antibody levels in Lipo-NES-DP immunized monkeys were 58,786 and 6213 mIU/mL. None of the challenged monkeys showed viremia and elevation in serum alanine amino transferase levels. Monkeys immunized with Lipo-NE-DP and Lipo-NES-DP exhibited a sterilizing immunity, indicating complete protection, whereas monkeys immunized with Lipo-NE-P showed limited viral replication. In conclusion, the liposome-complexed DNA-corresponding proteins of HEV and HBV induced protective humoral immune responses to both components in monkeys and are worth exploring further.

Present and future management of viral hepatitis

Viral hepatitis can result in important morbidity and mortality, with its impact on health conditioned by the specific type of hepatitis, the geographical region of presentation and the development and access to new drugs, among other factors. Most acute presentation forms are self-limiting and may even go unnoticed, with just a small percentage of cases leading to acute liver failure that may necessitate transplantation or even cause the death of the patient. However, when they become chronic, as in the case of hepatitis B virus and C virus, unless they are diagnosed and treated adequately they may have severe consequences, like cirrhosis or hepatocarcinoma. Understanding of the mechanisms of transmission, the pathogenesis, the presence of vaccinations and the development over recent years of new highly-efficient, potent drugs have meant that we are now faced with a new scenario in the management of viral hepatitis, particularly hepatitis B virus and hepatitis C virus. The spectacular advances in hepatitis C virus treatment have led the World Health Organization to propose the objective of its eradication by 2030. The key aspect to achieving this goal is to ensure that these treatments reach all the more vulnerable population groups, in whom the different types of viral hepatitis have a high prevalence and constitute a niche that may perpetuate infection and hinder its eradication. Accordingly, micro-elimination programs assume special relevance at the present time.

Contemporary strategy to control viral hepatitis A in the Russian Federation

The problem of choosing a strategy to control hepatitis A in the Russian Federation remains relevant for the health care of our country. By strategy we mean a scientifically based program of action that defines the priorities and resources needed to effectively control hepatitis A.

The aim of the work is to present a strategy to control hepatitis A in the Russian Federation, taking into account the realities of today. Based on the analysis of Russian and international studies, we present answers to the questions that should be addressed before the choosing a strategy to control hepatitis A in the Russian Federation. The low incidence of hepatitis A creates a false image of the favorable situation with this infection. The rationale is given to include vaccination against hepatitis A in the National Vaccination Schedule in the section of mandatory vaccinations. Routine vaccination of children aged 24 and 36 months will lay the foundation for future protection against this infection. We consider the creating a National Hepatitis A Vaccination Program as an important aim. The implementation of such a program will allow full control of hepatitis A in the Russian Federation.

Hepatitis A antibody persistence 8 and 10 years after 1-dose and 2-dose vaccination in children from Panama

BACKGROUND

Hepatitis A virus (HAV) remains a global public health concern, which is potentially growing in Latin America, due to an expected shift from high to intermediate endemicity levels. The use of HAV vaccines in pediatric national immunization programs (NIPs), either as a 2-dose or a 1-dose schedule, has been explored in Latin American countries; however, evidence demonstrating long-term protection in this population is limited in the region. We evaluated long-term antibody persistence following a 1-dose partial series and the recommended 2-dose schedule used in Panama's pediatric NIP.

METHODS

Two independent cross-sectional serological surveys were conducted at year 8 (Y8) and Y10 following vaccination under the NIP with 1 or 2 doses of an inactivated HAV vaccine (Havrix, GSK). Seropositivity (anti-HAV antibody concentration ≥ 15 mIU/mL) rates and antibody geometric mean concentrations (GMCs) were assessed at each serosurvey. Non-inferiority of 1 dose versus 2 doses was also explored.

RESULTS

This study (NCT02712359) included 600 and 599 children at Y8 and Y10 post-vaccination, respectively. Seropositivity rates were 74.3% (95% confidence interval [CI]: 69.0; 79.2) and 97.7% (95% CI: 95.3; 99.1) at Y8 and 71.9% (95% CI: 66.4; 76.9) and 96.3% (95% CI: 93.5; 98.2) at Y10, in the 1-dose and 2-dose groups, respectively. Antibody GMCs were lower in the 1-dose versus the 2-dose group in both surveys. Non-inferiority was not demonstrated since the lower limit of the 2-sided 95% CI for the between-group difference in seropositivity rates (1-dose minus 2-dose) was < -10%.

CONCLUSION

Anti-HAV antibody persistence was observed in lower percentages of children receiving 1 dose versus 2 doses of Havrix, at 8 and 10 years post-vaccination in Panama. Further investigations are needed to confirm antibody persistence and conclude on the protection afforded beyond 10 years in the pediatric population in Latin America.

Long-Term Persistence of Antibody Response with Two Doses of Inactivated Hepatitis A Vaccine in Children

INTRODUCTION

Hepatitis A virus infection is more severe in adults than children. Although vaccination can protect adults, current childhood programs cover a large population more successfully. Childhood vaccination is, therefore, a solution to protecting adults if it induces lasting immunity. Fifteen-year protection has been demonstrated in children, but longer-term data are only available for adults. We aimed to predict long term persistence of antibody in children beyond 15 years and assess if immunological mechanisms triggered by vaccination support longer-term protection.

METHODS

Long-term clinical studies using hepatitis A (HAV) or A/B vaccines (HAB) containing 720 or 1440 Enzyme-linked immunosorbent assay Units (EU) of hepatitis A virus antigen were identified. Duration of persistence of antibodies and possible protection was determined by descriptively comparing antibody geometric mean concentration (GMC) kinetics, as well as GMC (95% confidence interval) at 15 years post-vaccination across studies. Immunological mechanism studies describing hepatitis A vaccination were identified.

RESULTS

One study in children 12-15 years (2-dose HAB 720) and four in adults (2-dose HAV 1440 and 3-dose HAB 720) showed comparable GMC kinetics and per year rates of change up to 15 years. At 15 years, the GMC in children [414.7 mEU/ml (336.9; 510.5)] was in the same range as in adults [range 282.6 (217.6; 367.0) to 550.1 (416.0; 727.4)]. Based on these data, mathematical model predictions from adult studies (showing > 85% protected at 50 years) were deemed likely to also apply to children. Studies identified, both humoral and cell-mediated responses are induced following vaccination.

CONCLUSION

Based on comparable antibody data in adults and children up to 15 years, similar longer-term antibody persistence is expected in children with 2-dose inactivated hepatitis A 720 containing vaccine at least up to 50 years. Accordingly, improving routine childhood hepatitis A vaccination coverage could protect against more severe disease in adulthood. Fig. 1 Plain language summary TRIAL REGISTRATION: ClinicalTrials.gov identifiers, NCT00875485, NCT01000324, NCT01037114, NCT00289757, NCT00291876.

Immunization against Hepatitis A

Worldwide, there are multiple formaldehyde-inactivated and at least two live attenuated hepatitis A vaccines now in clinical use. The impressive immunogenicity of inactivated vaccines is reflected in rapid seroconversion rates, enabling both preexposure and postexposure prophylaxis. Universal childhood vaccination programs targeting young children have led to significant drops in the incidence of hepatitis A both in toddlers and in susceptible nonimmune adults in regions with intermediate endemicity for hepatitis A. Although the safety of inactivated vaccines is well established, further studies are needed concerning the implications of fecal virus shedding by recipients of attenuated vaccines, as well as the long-term persistence of immune memory in children receiving novel immunization schedules consisting of single doses of inactivated vaccines.

Persistence of immune memory among adults with normal and high antibody response to primary hepatitis B vaccination: Results from a five-year follow-up study in China

Immune memory after hepatitis B vaccination among adults is still under investigation. In this study, adults who had normal and high antibody response to the primary series of hepatitis B vaccination (HepB) were followed up at 5 years after the primary immunization. A booster dose was given to those who had low hepatitis B surface antibody (anti-HBs) titers, defined as anti-HBs levels < 10 mIU/mL. Blood samples were collected at two weeks after the booster and anti-HBs levels were measured. We assumed those with ant-HBs levels > = 10 mIU/mL after the booster had anamnestic response. In total, 242 persons completed the booster and the anti-HBs test. The anamnestic response rate was 99.59% (241/242) and geometric mean concentration (GMC) of anti-HBs after the booster was 2989 mIU/mL (95% CI: 255, 35085). Anti-HBs titer after the booster dose had a positive correlation with anti-HBs titers measured right after the primary immunization as well as anti-HBs titers 5 years later just before the booster. After the booster, no significant difference was found in anti-HBs titers between participants who were immunized with the 10μg HepB vaccine and those with the 20μg vaccine. Multivariable analysis showed that 1) vaccine brand used for the primary vaccination, 2) anti-HBs titers after primary vaccination and 3) anti-HBs titers before the booster dose were independently associated with the anti-HBs titers after the booster 1) β = -0.21, 95% CI: -0.33, -0.09, P = 0.001; 2) β = 0.07, 95% CI: 0.05, 0.09, P < 0.001; 3) β = 0.04, 95% CI: 0.02, 0.07, P < 0.001). In summary, anamnestic response exists among almost all adults at five years after HepB primary immunization. Vaccine brand used for primary vaccination, initial anti-HBs titers after primary immunization and anti-HBs titers before the booster were the independent predictive factors of HepB anamnestic response titers.

Hepatitis A, B, and A/B vaccination series completion among US adults: A claims-based analysis

Hepatitis A and B disease burden persists in the US. We assessed hepatitis A and hepatitis B vaccination series completion rates among 350,240 commercial/Medicare and 12,599 Medicaid enrollees aged ≥19 years. A vaccination series was considered as completed provided that the minimum interval between doses, as defined by the CDC, and the minimum number of doses were reached. We stratified completion rates by vaccine type (i.e. monovalent or bivalent) at initial vaccination for each cohort. In the commercial/Medicare cohort, the series completion rate was 32.0% for hepatitis A and 39.6% for hepatitis B among those who initiated with a monovalent vaccine, and it was 36.2% for hepatitis A and 48.9% for hepatitis B among those who initiated with a bivalent vaccine. In the Medicaid cohort, the series completion rate was 21.0% for hepatitis A and 24.0% for hepatitis B among those who initiated with a monovalent vaccine, and it was 19.0% for hepatitis A and 24.6% for hepatitis B among those who initiated with a bivalent vaccine. In conclusion, hepatitis A and B vaccination series completion rates were low, and appeared to be lower among Medicaid than among commercial/Medicare enrollees. Commercial/Medicare enrollees who initiated with a bivalent vaccine had higher series completion rates than those who initiated with monovalent vaccines - an observation that was not made among Medicaid enrollees.

Impact of universal mass vaccination with monovalent inactivated hepatitis A vaccines - A systematic review

The WHO recommends integration of universal mass vaccination (UMV) against hepatitis A virus (HAV) in national immunization schedules for children aged ≥1 year, if justified on the basis of acute HAV incidence, declining endemicity from high to intermediate and cost-effectiveness. This recommendation has been implemented in several countries. Our aim was to assess the impact of UMV using monovalent inactivated hepatitis A vaccines on incidence and persistence of anti-HAV (IgG) antibodies in pediatric populations. We conducted a systematic review of literature published between 2000 and 2015 in PubMed, Cochrane Library, LILACS, IBECS identifying a total of 27 studies (Argentina, Belgium, China, Greece, Israel, Panama, the United States and Uruguay). All except one study showed a marked decline in the incidence of hepatitis A post introduction of UMV. The incidence in non-vaccinated age groups decreased as well, suggesting herd immunity but also rising susceptibility. Long-term anti-HAV antibody persistence was documented up to 17 y after a 2-dose primary vaccination. In conclusion, introduction of UMV in countries with intermediate endemicity for HAV infection led to a considerable decrease in the incidence of hepatitis A in vaccinated and in non-vaccinated age groups alike.

Immunity to hepatitis A and B persists for at least 15 years after immunisation of adolescents with a combined hepatitis A and B vaccine

BACKGROUND

The exact duration of antibody persistence to hepatitis A and B and the need for booster dosing following primary immunisation remains undefined. A long-term study was designed to follow antibody persistence and immune memory on an annual basis for up to 15 years following vaccination during adolescence.

METHODS

Subjects received a combined hepatitis A and B vaccine (Twinrix™, GSK Vaccines, Belgium) at 12-15 years of age, either as 2-dose of the adult formulation or 3-dose of the paediatric formulation. Blood samples were taken every year thereafter to assess antibody persistence and immune memory to hepatitis A and B. Antibodies to hepatitis A virus (anti-HAV) and hepatitis B surface antigen (anti-HBs) were measured at Years 11-15. At Year 15 immune memory was further assessed by measuring the anamnestic response to a challenge dose of the monovalent vaccine, which was administered to subjects whose antibody concentrations fell below the pre-defined cut-offs (anti-HAV: <15mIU/mL; anti-HBs: <10mIU/mL).

RESULTS

209 subjects returned for follow-up at Year 15 of whom 162 were included in the long-term according-to-protocol immunogenicity cohort. All subjects remained seropositive for anti-HAV antibodies, while 81.1% and 81.8% still had anti-HBs antibodies ≥10mIU/mL in the 2- and 3-dose groups, respectively. Following hepatitis B vaccine challenge dose administration to 19 subjects, all except one in the 3-dose group, mounted a robust anamnestic response. The safety and reactogenicity profile of the hepatitis B challenge was consistent with previous experience.

CONCLUSION

Immunity to hepatitis A and B persists 15 years after adolescent vaccination with a combined hepatitis A and B vaccine. Highly effective anamnestic response indicates that a booster dose should not be required for 15 years after primary vaccination.

TRIAL REGISTRATION

http://www.clinicaltrials.govNCT00875485.

Meningococcal quadrivalent tetanus toxoid conjugate vaccine (MenACWY-TT, Nimenrix™): A review of its immunogenicity, safety, co-administration, and antibody persistence

INTRODUCTION

Meningococcal disease is a major cause of morbidity and mortality worldwide with reported epidemics and outbreaks in different parts of the world. Despite the availability of antimicrobial therapy, challenges remain in early recognition and prevention of disease. Several vaccines have been developed to date aiming at preventing disease spread.

DISCUSSION

MenACWY-TT (Nimenrix™) has been extensively studied for use in different age groups. Phase II and III randomized trials have demonstrated its immunogenicity when administered in children aged 1 year and older, adolescents and adults. It has an acceptable safety profile with minor adverse events comparable to other vaccines. Follow up studies have shown persistence of protective antibodies up to three years. MenACWY-TT was safely and effectively co-administered with different recommended vaccines.

CONCLUSION

MenACWY-TT is a safe and immunogenic vaccine that can be used to protect against these four serogroups in individuals older than 1 year of age.

Hepatitis B and A vaccination in HIV-infected adults: A review

Hepatitis B and A account for considerable morbidity and mortality worldwide. Immunization is the most effective means of preventing hepatitis B and A. However, the immune response to both hepatitis vaccines seems to be reduced in HIV-infected subjects. The aim of this review was to analyze the immunogenicity, safety, long-term protection and current recommendations of hepatitis B and A vaccination among HIV-infected adults. The factors most frequently associated with a deficient level of anti-HBs or IgG anti-HAV after vaccination are those related to immunosuppression (CD4 level and HIV RNA viral load) and to the frequency of administration and/or the amount of antigenic load per dose. The duration of the response to both HBV and HAV vaccines is associated with suppression of the viral load at vaccination and, in the case of HBV vaccination, with a higher level of antibodies after vaccination. In terms of safety, there is no evidence of more, or different, adverse effects compared with HIV-free individuals. Despite literature-based advice on the administration of alternative schedules, revaccination after the failure of primary vaccination, and the need for periodic re-evaluation of antibody levels, few firm recommendations are found in the leading guidelines.

Comparison of different genotyping methods for hepatitis B virus in a Chinese population

AIM: To genotype hepatitis B virus (HBV) in college students who tested positive HBsAg, HBeAg, and HBcAb using three different methods and compare the advantages and disadvantages of these genotyping methods.

METHODS: According to the specificity of HBV-S, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or direct genotyping based on the length of PCR amplified fragment were used for HBV genotyping. By means of homology alignment of 220 items of HBV-S gene sequences with HBV-B/C/D type identified in NCBI database, a molecular evolutionary tree as a genotyping standard has been constructed. The test samples were genotyped by carrying out HBV-S gene PCR amplification, sequencing, alignment and constructing an HBV-S region evolutionary tree together with the standard phylogenic tree.

RESULTS: In a total of 216 HBV positive samples, the genotyping result of PCR-RFLP was: genotype B, 155; genotype C, 41; genotype D, 7; Unknown, 13. Of these unknown cases, 10 were identified as genotype C by the direct genotyping method based on the length of PCR amplified fragment, and 3 were still determined. The genotyping results for 30 selected samples were substantially different between the method of the sequencing-evolutionary tree and PCR-RFLP. Three cases of HBV genotype G, which come from the men of Zhuang and Yao nationalities in Guangxi, were first discovered in China using the sequencing-evolutionary tree method.

CONCLUSION: The three genotyping methods have different advantages and disadvantages: PCR-RFLP can distinguish between sub-genotypes, but can not distinguish C2 and D2; direct genotyping method based on PCR amplified fragment size is simple and direct, but its accuracy and specificity are not high; the sequencing-evolutionary tree method is accurate and specific, representing a "golden" standard for HBV genotyping.

A tetravalent meningococcal serogroups A, C, W-135, and Y tetanus toxoid conjugate vaccine is immunogenic and well-tolerated when co-administered with Twinrix(®) in subjects aged 11-17 years: an open, randomised, controlled trial

The co-administration of the tetravalent meningococcal conjugate vaccine, MenACWY-TT, with a licensed hepatitis A and B vaccine, HepA/B (Twinrix(®)), was compared to their separate administration in this open, randomised, controlled study. Healthy subjects 11-17 years of age (n=611) were randomised (3:1:1) to receive both vaccines, MenACWY-TT alone or HepA/B alone. The co-administration of both vaccines was shown to be non-inferior to their individual administration. At seven months after the first vaccination, 99.4-100% of the subjects who received both vaccines co-administered showed seroprotection against all meningococcal serogroups and at least 99.1% of them were seropositive for hepatitis A and seroprotected against hepatitis B. This study suggests that MenACWY-TT vaccine could be co-administered with HepA/B without adversely impacting the immunogenicity, safety and reactogenicity of either of the vaccines.

Seroprevalence and risk factors for hepatitis B infection in an adult population in Northeast China

BACKGROUND AND AIM

The prevalence of the hepatitis B virus (HBV) is higher in adults than in children. We determined the seroepidemiology of HBV infection in an adult population in JiLin, China, to guide effective preventive measures.

METHODS

A cross-sectional serosurvey was conducted throughout JiLin, China. A total of 3833 people was selected and demographic and behavioral information gathered. Serum samples were tested for HBV markers and liver enzymes.

RESULTS

The prevalence of the hepatitis B surface antigen (HBsAg), the antibody to the hepatitis B surface antigen (anti-HBs), the hepatitis B e antigen (HBeAg), the antibody to HBeAg (anti-HBe), and the antibody to the hepatitis B core antigen (anti-HBc) were 4.38%, 35.66%, 1.38%, 6.65%, and 40.88%, respectively. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly higher among HBsAg (+) than HBsAg (-) subjects. By multivariate logistic regression analysis, independent predictors for chronic HBV infection were smoking, poor sleep quality; occupation as private small-businessmen, laborers, or peasants; male gender; family history of HBV; personal history of vaccination; and older age. Independent predictors for exposure to HBV were large family size, occupation as a private small-businessman, male gender, family history of HBV, personal history of vaccination, and older age. Independent predictors for immunity by vaccination were occupation as a private small-businessman, high income, personal history of vaccination, and young age. Independent predictors for immunity by exposure were drinking, male gender, personal history of vaccination, and older age.

CONCLUSIONS

The prevalence rate of HBV infection (4.38%) was lower than the previous rate of general HBV vaccination. However, 44.59% of the population remained susceptible to HBV. The prevalence of HBV infection was high in young adults, private small-businessmen, peasants, those with a family history of HBV, and males. Therefore, immunization of the non-immune population is reasonable to reduce hepatitis B transmission between adults.

Development of candidate combination vaccine for hepatitis E and hepatitis B: a liposome encapsulation approach

To reduce extra injections, cost and ensure better coverage, use of combination vaccines is preferable. An attempt was made to evaluate the encapsulation of hepatitis E virus neutralizing epitope (NE) region and hepatitis B virus surface antigen (HBsAg) in liposomes as DNAs, proteins and DNA+protein. Mice groups were immunized with different liposome-encapsulated formulations and monitored for anti-HEV and anti-HBs titres, IgG subtypes, antigen-specific lymphocyte proliferation and cytokine levels. The protective levels of anti-HBs and in vitro virus-binding capacity of anti-HEV antibodies were assessed. Liposome-encapsulated DNA either singly or in combination did not elicit antibody response. Anti-HEV and anti-HBs IgG titres of individual component of protein alone (Lipo-E-P/Lipo-B-P) or DNA+protein formulations (Lipo-E-DP/Lipo-B-DP) were comparable to respective titres in combination vaccine of protein (Lipo-BE-P) and DNA+protein formulations (Lipo-BE-DP). IgG1 levels were significantly higher in Lipo-BE-P group whereas, equivalent levels of IgG1 and IgG2a were observed in Lipo-BE-DP group against both components of the vaccine. Combination vaccine group showed mixed Th1/Th2 cytokine profile. Liposome entrapped NE and HBsAg in protein and DNA+protein formats induce excellent immune response to both the components and need to be evaluated in higher animals.

The need for an evidence-based decision-making process with regard to control of hepatitis A

Universal hepatitis A (HA) vaccination was implemented by the Argentinean Ministry of Health in June 2005 with a single dose at age 12 months. The decision was made taking into account the following factors. (1) Disease burden: The incidence rate for the disease increased from 2003 to 2004; the northern and western regions of the country were the most affected. Sero-prevalence data for children 1-15 years old was 54% for the whole country, with differences per region and age. From May 1982 to September 2002, 210 patients were recruited with acute hepatic failure; HA was the aetiology in 61% of them. (2) Cost-effectiveness: Compared with no vaccination, the one-dose schedule would save US$15.3 millions, with regional variations. (3) Vaccine features: Immunization with one-dose schedule HA vaccine confers good immunogenicity and effectiveness. (4) Programmatic feasibility: The National Immunizations Program has appropriate distribution system for vaccines, with adequate cold chain. (5) Social acceptance and political compromise: The population largely accepts HA vaccination and the national authorities should be committed to providing it regularly. The main global issue is that hepatitis A virus infection remains the most commonly reported vaccine-preventable disease in many parts of the world despite the availability of vaccines.

New antiviral choice for chronic hepatitis B: tenofovir disoproxil fumarate

Tenofovir disoproxil fumarate (TDF) is an oral prodrug of tenofovir, a novel, acyclic nucleotide analogue with in vitro activity against HIV-1 and HIV-2. TDF is licensed by American Food and Drug Administration (FDA) in 2001 for the treatment of HIV infection. TDF is currently one of the most widely used nucleotide reverse transcriptase inhibitors (NRTIs) for the treatment of HIV infection. Its efficacy, favorable toxicity profile, and convenient dosing have made this drug one of the most popular first-line treatment. Numerous studies have demonstrated the use of TDF in the treatment of HIV infection. It also has been shown to be effective in HIV/HBV coinfected patients and in patients with wild-type and lamivudine-resistant strains. Accumulating evidence suggests that TDF is more potent in suppressing HBV replication. In this review, we summarize the study progress of TDF in treating HBV infection.

Therapeutic effect of adeforvir dipivoxil for HBeAg-positive patients with chronic hepatitis B

AIM: To verify the efficacy and safety of adeforvir dipivoxil in the treatment of HbeAg-positive chronic hepatitis B (CHB).

METHODS: A total of 40 HbeAg-positive patients with CHB were divided into group A (n = 26) and B (n = 14). The patients in group A and B were treated with adeforvir dipivoxil (10 mg/d) and placebo, respectively, for 12 wk, and then all the patients were treated with adeforvir dipivoxil (10 mg/d). The responses were observed 12, 24, and 48 wk after treatment, and the hepatitis B virus markers (HBVMs), and HBV DNA, liver function, kidney function, blood routine and urine routine were also measured.

RESULTS: After 12 wk of treatment, the viral response rates were significantly different between group A and B (80.77% vs 7.14%, P < 0.01); the ALT/AST normalization rates had no marked difference between the two groups. After 48 wk of treatment, the viral response rates in both groups were 78.38%, and the ALT/AST normalization rates were 59.46%; the levels of ALT, AST and TBiL level reduced significantly (t = 5.19, 4.48, 2.47, P < 0.01) compared with those before treatment, and the HbeAg-negative rates were 18.92%. No severe adverse reactions were found in both groups.

CONCLUSION: Adeforvir dipivoxil has obvious effect on viral and biochemical responses in CHB patients, and it is effective and safe in the treatment of CHB.

Bivalent inactivated hepatitis A and recombinant hepatitis B vaccine

Hepatitis A and B remain serious global public health problems. Monovalent vaccines against hepatitis A and B have been available for many years. Since 1996, licenses have been gradually introduced for different formulations and immunization schedules of the first combined vaccines against both diseases. Twinrix Adult (with conventional and accelerated schedules) is available for the immunization of individuals aged 16 years or older in Europe and 18 years or older the USA. Twinrix Pediatric, with its three-dose schedule, and AmBirix, with its two-dose schedule, are licensed in Europe for ages 1-15 years. These vaccines offer a single injection for satisfactory protection against hepatitis A and B and an excellent safety and reactogenicity profile in comparison with monovalent vaccines. This article focuses on immunogenicity of the vaccines and proposes expert opinion and future directions in this field.

Long-term antibody persistence induced by a combined hepatitis A and B vaccine in children and adolescents

Two cohorts, comprising of subjects aged 1-6 years and 6-15 years were vaccinated with Twinrix according to a 0-, 1- and 6-month schedule. The 1-6 years cohort was followed up for 7.5 years and the 6-15 years cohort for 10 years. At the latest follow-up time point, all subjects were seropositive for anti-HAV antibodies, while 86.5% (32/37) and 95.5% (21/22) had anti-HBs >or= 10 mIU/ml in the 1-6 years and in the 6-15 years cohort. The geometric mean concentrations (GMCs; mIU/ml) were 233 and 680 for anti-HAV antibodies, and 147 and 165 for anti-HBs antibodies, in the 1-6 years and 6-15 years cohorts, respectively. The high persistence of circulating anti-HAV and anti-HBs antibodies in children and adolescents demonstrates the long-term protection offered by Twinrix in these age groups.

Epidemiology of travel-associated and autochthonous hepatitis A in Austrian children, 1998 to 2005

BACKGROUND

In Austria, being an area of low hepatitis A endemicity, every year, several cases of this infectious disease are reported. The aim of the present study was to provide data on disease and hospitalization of children below the age of 15 for imported and autochthonous hepatitis A in Austria.

METHODS

Nationwide, active, hospital-based surveillance during the period 1998 to 2005.

RESULTS

During this 8-year observation period, 413 children below 15 years of age were hospitalized with acute hepatitis due to infection with hepatitis A . The mean annual incidence of hospitalization per 100,000 population was 3.8, with a decreasing trend from 1998 to 2005. The mean length of hospital stay attributable to hepatitis A was 6.5 days. The mean annual number of days of hospitalization attributable to acute hepatitis A infection in children below 15 years of age was 335 days. Information on origin of infection was available in 48% of the reports, the majority of which (69%) were in consequence of infection import. The mean annual incidence of travel-associated, hospitalized hepatitis A cases was 1.3 per 100,000, showing a lesser decrease rate over the observation period than the total hospitalization incidence.

CONCLUSIONS

In an area of low hepatitis A endemicity such as Austria, hospitalization incidence of children is still at a considerable level. Our findings contribute to an open discussion about universal childhood vaccination.

Severe necrotizing pancreatitis following combined hepatitis A and B vaccination

Necrotizing pancreatitis is a severe form of pancreatitis and is associated with substantial morbidity and mortality. We report a case of necrotizing pancreatitis that developed following combined hepatitis A and B vaccination. No other causes of pancreatitis could be determined. Although confirming the diagnosis is challenging, 3 main factors suggest a possible link to the vaccine: the chronology of the events, the patient's human leukocyte antigen genotype and the incongruent immune response to the vaccine components. This report serves to alert physicians to the possible development of necrotizing pancreatitis after vaccination.

A review of the long-term protection after hepatitis A and B vaccination

Vaccine-preventable viral hepatitis continues to be a cause of considerable morbidity and mortality: on worldwide basis, approximately 1.4 million cases of hepatitis A are reported every year. The true incidence, however, has been estimated to be 3-10 times higher. Regarding hepatitis B, more than a third of the world's population has been infected. The World Health Organization has estimated (2000) that there are 367 million chronic carriers of hepatitis B worldwide, and approximately 1 million deaths per year as a consequence of chronic complications and acute fulminant disease. Hepatitis B vaccines have been licensed since 1982, and hepatitis A vaccines since 1992. In 1996, a combined hepatitis A and B vaccine became available. An update on the long-term protection conferred by hepatitis A and hepatitis B vaccines as well as the combined hepatitis A and B vaccine is offered in this paper. Long-term efficacy and booster policy for hepatitis B vaccines have often been a topic of discussion. Based on current data and field experience there is, in general, no necessity for booster doses for fully vaccinated immunocompetent individuals. Long-term protection has been demonstrated by the rapid (5-7 days) development of anamnestic antibody responses among vaccinees who no longer have detectable anti-HBs. Anamnestic responses correlate with lymphoproliferative T-cell responses following challenge with hepatitis B vaccine. Furthermore, employing Spot-ELISA techniques, circulating B-cells were shown to be able to produce anti-HBs in vaccinees who lost their detectable antibodies. The accumulated data from a large number of studies indicate that despite antibody decline or loss, immune memory exhibits long-term persistence. There is somewhat less information available for hepatitis A vaccines, yet an increasing number of studies indicate that the findings for hepatitis B vaccines are also applicable to hepatitis A vaccines. The necessity to provide a booster dose was based on early projections of observed antibody levels. However, recent follow-up studies with up to 12 year observation, as well as studies employing mathematical models predict that following primary vaccination, antibodies will persist for at least 25 years. In addition, experimental studies confirm that vaccination against hepatitis A induces immunological memory. Therefore hepatitis A booster vaccination is presently considered as unnecessary in fully vaccinated individuals. The above findings are of importance in the context of administering combined hepatitis A and B vaccine for which similar long-term data have been observed. All available data on monovalent and combined hepatitis A and hepatitis B vaccines indicates that there is no support for a hepatitis A or hepatitis B booster when a complete primary vaccination course is offered to immunocompetent individuals.

Ten-year antibody persistence induced by hepatitis A and B vaccine (Twinrix) in adults

BACKGROUND

Hepatitis A and B infections are prevalent worldwide and cause significant morbidity and mortality. A combined vaccine providing dual protection against hepatitis A and B is available (Twinrix, GlaxoSmithKline Biologicals).

METHOD

Two cohorts of adults aged 17-43 years were vaccinated with Twinrix according to a 0, 1, 6 months schedule and followed up for 10 years.

RESULTS

One month after the primary vaccination course (Month 7), all subjects were seropositive for anti-HAV and all had anti-HBs> or = 10 mIU/ml. At month 120, 100% of subjects (N=34; N=29) in both cohorts were seropositive for anti-HAV; 94.1% and 86.2% of subjects had anti-HBs > or = 10 mIU/ml. The geometric mean concentrations (GMC; mIU/ml) were 373.9 and 674.6 in the two cohorts for anti-HAV, and 103.8 and 320.0, respectively, for anti-HBs. None of the serious adverse events reported throughout the follow-up period were considered by the investigator to be causally related to vaccination.

CONCLUSIONS

Combined hepatitis A and B vaccine, Twinrix, is safe, well-tolerated and has demonstrated a highly immunogenic profile. Persistence of anti-HAV and anti-HBs antibodies in adults remains high for at least 10 years after primary vaccination.

Primary Hepatitis A vaccination failure is a rare although possible event: results of a retrospective study

A case of Hepatitis A occurred in a traveller in spite of a complete course of immunization with a combined HAV and HBV vaccine [Taliani G, Sbaragli S, Bartoloni A, Santini MG, Tozzi A, Paradisi F. Hepatitis A vaccine failure: how to treat the threat. Vaccine 2003;21(31):4505-6]. A retrospective study was performed to evaluate whether the failure was primary or could be attributed to a specific lot of vaccine or to its inadequate handling and/or storage. Two distinct populations of vaccinees were selected in a 1:2 proportion. The case group (N=31) included subjects who were vaccinated in the same period and with the same lot and batch of vaccine as the case. The control group (N=62) included subjects who received different lot and batch of the same vaccine as the case group. A persisting antibody response to HAV vaccine was found among all subjects (anti-HAV >20mIU/ml). The overall anti-HBs seropositivity rate (anti-HBs >10mIU/ml) was 74%, without significant difference between the case (77%) and the control group (73%; P>0.05). The reported Hepatitis A case can be attributed to a rare primary vaccine failure rather than to inefficacy of a specific lot of vaccine or to inappropriate vaccine handling or storage. Our study supports the indications for use of combined Hepatitis A+B immunization in travellers at risk for both infections, but stresses the need for information on correct hygienic behaviours while abroad.

Hepatitis A/B vaccination of adults over 40 years old: Comparison of three vaccine regimens and effect of influencing factors

Challenged by contrasting data on low immune responses in the elderly with a combined hepatitis A/B vaccine, a randomised, controlled study was conducted to assess the immunogenicity of three hepatitis A and B vaccination regimens (group 1: combined hepatitis A/B vaccine Twinrix [GSK]; group 2: co-administered hepatitis A vaccine, Havrix [GSK]+hepatitis B vaccine Engerix -B [GSK], group 3: co-administered hepatitis A vaccine, Vaqta [Sanofi-Pasteur MSD]+hepatitis B vaccine HB VAX PRO [Sanofi-Pasteur MSD]) and the effect of influencing factors in subjects >40 years. On completion of the full vaccination course, anti-HBs seroprotection (SP) rates were 92, 80 and 71% in groups 1, 2 and 3, respectively; anti-HAV seropositivity (S+) rates were 97, 99 and 99%, respectively. In group 1, anti-HBs SP rate was non-inferior as well as superior and anti-HAV S+ rate was non-inferior to that in groups 2 and 3. Anti-HBs response was most significantly influenced by the vaccine regimen, followed by age, gender and BMI (stepwise multiple regression analysis). BMI had the most significant influence on HAV response followed by age, gender and vaccine regimen. In conclusion, Twinrix induced superior hepatitis B SP rates and similar hepatitis A S+ rates compared to concomitant administration of monovalent vaccines in subjects aged >40 years.

Hepatitis A and B Booster Recommendations: Implications for Travelers

Hepatitis A and B are serious vaccine-preventable diseases with a predominantly overlapping epidemiological distribution. Travelers, a term encompassing a range of individuals, are at risk of contracting these diseases if they are unvaccinated. Although the benefits of the primary vaccination course of hepatitis A and B vaccines are clear, the administration of hepatitis A and B boosters varies worldwide. Recommendations on the need for booster vaccinations have recently been published, and the implications of these recommendations for travelers are discussed in this review. Until a greater understanding is reached on the immunogenicity of hepatitis A and B vaccines in certain special groups (e.g., immunocompromised persons), there will be a need to monitor antibody levels to assess whether booster vaccinations are required. However, for the majority of immunocompetent travelers, the full primary vaccination course will provide protection from both hepatitis A and B infection in the long term, without the need for boosters.