Comparative immunogenicity and safety of two dosing schedules of a combined hepatitis A and B vaccine in healthy adolescent volunteers: an open, randomised study

Hepatitis A immunisation in persons not previously exposed to hepatitis A

This review is withdrawn because it is outdated. A new review is to be published by the end of 2019.

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.

Immunogenicity, effectiveness and safety of combined hepatitis A and B vaccine: a systematic literature review

BACKGROUND

Hepatitis A and B are two of the most common vaccine-preventable diseases and vaccination for Hepatitis A virus (HAV) and hepatitis B virus (HBV) is recommended for those at risk of contracting HAV and/or HBV through their occupation, travel or lifestyle.

OBJECTIVE

To describe the vaccine efficacy, immunogenicity, effectiveness and safety of the combined vaccine against hepatitis A and hepatitis B.

METHODS

A systematic review of the literature published between 1990 and 2015.

RESULTS

Anti-HAV seropositivity rates ranged from 96.2% to 100% and anti-HBs seroprotection rates from 82% to 100%. Antibodies persisted up to 15 years and geometric mean concentration (GMC) remained above the seropositivity cut-off value for both. Anti-HAV and anti-HBs immune responses were lower in less immunocompetent individuals one month after completion of the immunization schedule. The safety profiles of Twinrix(TM) and monovalent hepatitis A and B vaccines were similar.

CONCLUSION

The vaccine offers satisfactory long-term immunogenicity rates, expected duration of protection and safety profile similar to the monovalent hepatitis A or B vaccines.

Hepatitis A immunisation in persons not previously exposed to hepatitis A

BACKGROUND

In many parts of the world, hepatitis A infection represents a significant cause of morbidity and socio-economic loss. Whilst hepatitis A vaccines have the potential to prevent disease, the degree of protection afforded against clinical outcomes and within different populations remains uncertain. There are two types of hepatitis A virus (HAV) vaccine, inactivated and live attenuated. It is important to determine the efficacy and safety for both vaccine types.

OBJECTIVES

To determine the clinical protective efficacy, sero-protective efficacy, and safety and harms of hepatitis A vaccination in persons not previously exposed to hepatitis A.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and China National Knowledge Infrastructure (CNKI) up to November 2011.

SELECTION CRITERIA

Randomised clinical trials comparing HAV vaccine with placebo, no intervention, or appropriate control vaccines in participants of all ages.

DATA COLLECTION AND ANALYSIS

Data extraction and risk of bias assessment were undertaken by two authors and verified by a third author. Where required, authors contacted investigators to obtain missing data. The primary outcome was the occurrence of clinically apparent hepatitis A (infectious hepatitis). The secondary outcomes were lack of sero-protective anti-HAV immunoglobulin G (IgG), and number and types of adverse events. Results were presented as relative risks (RR) with 95% confidence intervals (CI). Dichotomous outcomes were reported as risk ratio (RR) with 95% confidence interval (CI), using intention-to-treat analysis. We conducted assessment of risk of bias to evaluate the risk of systematic errors (bias) and trial sequential analyses to estimate the risk of random errors (the play of chance).

MAIN RESULTS

We included a total of 11 clinical studies, of which only three were considered to have low risk of bias; two were quasi-randomised studies in which we only addressed harms. Nine randomised trials with 732,380 participants addressed the primary outcome of clinically confirmed hepatitis A. Of these, four trials assessed the inactivated hepatitis A vaccine (41,690 participants) and five trials assessed the live attenuated hepatitis A vaccine (690,690 participants). In the three randomised trials with low risk of bias (all assessing inactivated vaccine), clinically apparent hepatitis A occurred in 9/20,684 (0.04%) versus 92/20,746 (0.44%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.03 to 0.30). In all nine randomised trials, clinically apparent hepatitis A occurred in 31/375,726 (0.01%) versus 505/356,654 (0.18%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.05 to 0.17). These results were supported by trial sequential analyses. Subgroup analyses confirmed the clinical effectiveness of both inactivated hepatitis A vaccines (RR 0.09, 95% CI 0.03 to 0.30) and live attenuated hepatitis A vaccines (RR 0.07, 95% CI 0.03 to 0.17) on clinically confirmed hepatitis A. Inactivated hepatitis A vaccines had a significant effect on reducing the lack of sero-protection (less than 20 mIU/L) (RR 0.01, 95% CI 0.00 to 0.03). No trial reported on a sero-protective threshold less than 10 mIU/L. The risk of both non-serious local and systemic adverse events was comparable to placebo for the inactivated HAV vaccines. There were insufficient data to draw conclusions on adverse events for the live attenuated HAV vaccine.

AUTHORS' CONCLUSIONS

Hepatitis A vaccines are effective for pre-exposure prophylaxis of hepatitis A in susceptible individuals. This review demonstrated significant protection for at least two years with the inactivated HAV vaccine and at least five years with the live attenuated HAV vaccine. There was evidence to support the safety of the inactivated hepatitis A vaccine. More high quality evidence is required to determine the safety of live attenuated vaccines.

Antibody persistence and immune memory in adults, 15 years after a three-dose schedule of a combined hepatitis A and B vaccine

A combined hepatitis A and B vaccine is available since 1996. Two separate open-label primary studies evaluated the immunogenicity and safety of this hepatitis A and B vaccine (720 EI.U of HAV and 20 µg of HBsAg) in 306 healthy subjects aged 17-43 years who received three doses of the vaccine following a 0, 1, and 6 months schedule. These subjects were followed up annually for the next 15 years to evaluate long-term persistence of anti-HAV and anti-HBs antibodies. The subjects whose antibody concentrations fell below the cut-offs between Year 11 and Year 15 (anti-HAV: <15 mIU/ml; anti-HBs: <10 mIU/ml) were offered an additional dose of the appropriate monovalent hepatitis A and/or B vaccine. In subjects who received the additional vaccine dose, a blood sample was collected 1 month after vaccination. At the Year 15 time point, all subjects in Study A and Study B were seropositive for anti-HAV antibodies and 89.3% and 92.9% of subjects in the respective studies had anti-HBs antibody concentrations ≥10 mIU/ml. Four subjects (two in each study) received an additional dose of monovalent hepatitis B vaccine and mounted anamnestic responses to vaccination. No vaccine-related serious adverse events were reported. This study confirms the long-term immunogenicity of the three-dose regimen of the combined hepatitis A and B vaccine, as eliciting long-term persistence of antibodies and immune memory against hepatitis A and B for up to at least 15 years after a primary vaccination.

Hepatitis B surface antigen-1018 ISS adjuvant-containing vaccine: a review of HEPLISAV™ safety and efficacy

Immunization represents the most effective approach to the prevention of hepatitis B virus infection and the long-term complications of chronic disease, including liver cancer and liver failure. Current vaccines require three doses to achieve maximal immunogenicity and fail to produce long-lasting protection in 5-10% of immune-competent individuals and in a much larger proportion of immune-compromised patients. Immunostimulatory DNA sequence (ISS) vaccine adjuvants, when combined with vaccine antigens, may increase immunogenicity and reduce the number of required doses to achieve this goal. 1018 ISS plus recombinant hepatitis B surface antigen has been demonstrated to achieve these goals in immune competent and vaccine-hyporesponsive populations without compromising recipient safety.

Long-term immunogenicity and immune memory after two doses of the adult formulation of a combined hepatitis A and B vaccine in children 1 to 11 years of age

Long-term persistence of antibodies against hepatitis A and B (anti-HAV and anti-HBs) were evaluated in 1- to 11-year-old children following 2 doses (0, 6 months) of hepatitis A and B vaccine. Ten years postvaccination, all subjects were anti-HAV seropositive (≥15 mIU/mL), 81.7% had anti-HBs antibody concentrations ≥10 mIU/mL. All subjects with anti-HBs concentrations <10 mIU/mL, mounted a vigorous anamnestic response to an HBV vaccine challenge dose indicating the presence of immunologic memory against hepatitis B.

The use of dried blood spots for assessing antibody response to hepatitis A virus after natural infection and vaccination

During recent years, vaccination against hepatitis A has been implemented in several countries. It is expected that the increase in mass vaccination against hepatitis A will eventually result in a decreased prevalence of anti-HAV antibodies in the general population. For this reason, a suitable clinical sample for diagnosis of hepatitis A must be sufficiently sensitive to enable detection of lower antibodies titers. In this study, the feasibility of using dried blood spots (DBS) was assessed for the detection of anti-HAV antibodies after a natural infection and vaccination. Seventy-four DBS and paired plasma samples were obtained from a group of college students for a cross-sectional hepatitis A seroepidemiological study. Forty-six students seronegative for anti-HAV were selected randomly and immunized with an inactivated hepatitis A vaccine using an 0-6 month schedule. Seroconversion was monitored in paired plasma and DBS samples 6 months after the first dose followed by a period of 8 and 24 months after the second dose. A strong correlation between OD/CO rates of paired plasma and DBS samples for the detection of anti-HAV was observed. The sensitivity and specificity of the DBS compared with plasma for the detection of anti-HAV antibodies after natural infection was 100%. The sensitivity of DBS in samples collected 24 months after the second dose of hepatitis A vaccine was 95.4%. The results showed that DBS samples can be used for the detection of anti-HAV antibodies both after natural infection or vaccination.

Comparative immunogenicity of two vaccination schedules of a combined hepatitis A and B vaccine in healthy volunteers

In 1996, a combined vaccine against both hepatitis A and B was licensed and commercialized and has been recommended for healthcare personnel in Belgium. This study compares the immunogenicity against hepatitis B virus (HBV) and safety of two vaccination schedules (0-1-12 months and 0-1-6 months) with this vaccine. This is a randomized, stratified and controlled study in healthy adult workers, who are not occupationally exposed to HBV. Seroconversion (≥1 IU/L) and seroprotection (≥10 IU/L) rates were compared using Fisher's exact test; geometric mean concentrations (GMCs) of anti-HBs were compared using one-way ANOVA. All statistical analyses were carried out with SPSS 11 on Apple Macintosh. A total of 399 subjects were enrolled in the study, and 356 were analysed according to the protocol. The rate of ≥10 IU/L at 6 months was 70.6% in the group 0-1-12 and 79.9% in the group 0-1-6; this rate decreased to 55.9% at 12 months in the first group. Seroconversion and seroprotective rates against HBV measured at month 13 in group 0-1-12 (98.9% and 95.6%) and measured at month 7 in group 0-1-6 (99.4% and 97.1%) were not statistically significantly different. GMC of anti-HBs after the 0-1-12 schedule was more than two fold higher than after 0-1-6 schedule (P < 0.001). Reported side effects were comparable in both groups with a slight tendency to fewer side effects in the 0-1-12 group after the third dose. The results from our study show that the completed schedule 0-1-12 offers at least equal protective immunogenicity against HBV as the completed 0-1-6 schedule. People not receiving their third dose at 6 months can be given this dose up to 12 months after the first dose. The drawback of this flexibility, however, is the longer time period before the protection becomes effective.

Randomized trial to determine safety and immunogenicity of two strategies for hepatitis B vaccination in healthy urban adolescents in the United States

BACKGROUND

Multiple studies have shown excellent response rates after hepatitis B immunization in youth; however, one previous study conducted in urban youth demonstrated poor responses.

METHODS

Urban youth, ages 12 to 17 years, at participating Adolescent Medicine Trials Network for HIV/AIDS Interventions Clinical/Research sites were randomized to receive either 2 doses of Recombivax HB (10 microg hepatitis B surface antigen) or Twinrix (20 microg hepatitis B surface antigen and 720 EL.U hepatitis A antigen) at 0 and 24 weeks. Safety data were collected and antibody measures performed at 0, 28, and 76 weeks.

RESULTS

A total of 123 subjects were enrolled and 102 had week 28 serum samples available for antibody measure. A positive response (serum antibody > or =10 mIU/mL) to hepatitis B antigen was documented in 41 of 47 (87.2%; 95% confidence interval [CI] 74.3%-95.2%) Recombivax HB recipients and in 52 of 55 (94.6%; 95% CI, 84.9%-98.9%) Twinrix recipients (P = 0.295). In an adjusted analysis, those identified as Hispanic ethnicity (N = 86) were more likely to have a positive response (odds ratio 7.38, 95% CI, 1.56-34.95; P = 0.0018); whereas those who identified as not heterosexual (N = 9) were less likely to respond (odds ratio = 0.12, 95% CI, 0.02-0.74). The majority of youth in the Twinrix arm were hepatitis A antibody positive at baseline (26/51; 51%); however, 24 of 25 hepatitis A antibody negative youth responded to the hepatitis A component. Both vaccines were safe.

CONCLUSIONS

Response rate to 2 doses of Recombivax HB in urban youth is lower than previous studies suggest. The factors associated with diminished response are not known.

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.

Comparative efficacy of two dosages of recombinant hepatitis B vaccine in healthy adolescents in India

BACKGROUND

Inclusion of hepatitis B vaccine in the Universal Programme of Immunization of all Asian and African countries is hampered by the economic burden on the health budget because of the cost of hepatitis B vaccines. Here we evaluated the immunogenicity, safety, efficacy, and the persistence of antibody to hepatitis B surface antigen (anti-HBs) titers of a new and a low cost recombinant hepatitis B vaccine GeneVac B, with 2 different dosages in healthy adolescents in India.

METHODS

GeneVac-B, a recombinant hepatitis B vaccine (Serum Institute of India, Pune, India), was administered in 10 or 20 microg dose intramuscularly to 2 groups of 100 healthy school-going adolescents at 0-, 1-, and 6-month intervals, who were followed up for 1 year. Group I received 20 mug doses whereas Group II received 10 mug doses. Blood samples were collected 1 month after each dose and 1 year after the third dose. The anti-HBs titers were assayed using commercially available kits to assess the immunogenicity of the 2 dosage schedules. Safety studies were also carried out.

RESULTS

The geometric mean titer value of the anti-HBs titer 1 month after the third dose was 2629 (mlU/mL) in Group I and 1373 mlU/mL for Group II subjects. One year after the third dose, the persistence of anti-HBs in those who had received 20 mug was 2262 mlU/mL whereas it was 1039 mlU/mL in the group receiving 10 microg doses. All the subjects in both the groups were seroprotected at 1 year after vaccination. None of the vaccinees exhibited serious adverse reactions throughout the study period.

CONCLUSIONS

The study demonstrated the immunogenicity of the recombinant hepatitis B vaccine, and confirms that the 0.5 mL (10 microg) dose of GeneVac B can be administered with satisfactory safety and immunogenicity to adolescents up to 19 years of age, reducing the cost to less than U.S. $1.00 per dose making it acceptable for the Universal Programme of Immunization of developing and under developed countries.

Convenience is the key to hepatitis A and B vaccination uptake among young adult injection drug users

BACKGROUND

Despite CDC recommendations to vaccinate injection drug users (IDUs) against hepatitis A virus (HAV) and hepatitis B virus (HBV) infections, coverage remains low. Vaccination programs convenient to IDUs have not been widely implemented or evaluated. We assessed whether convenience and monetary incentives influenced uptake of free vaccine by 18-30-year-old IDUs in five U.S. cities.

METHODS

IDUs recruited from community settings completed risk behavior self-interviews and testing for antibodies to HAV (anti-HAV) and hepatitis B core antigen (anti-HBc). Vaccine was offered presumptively at pre-test (except in Chicago); on-site availability and incentives for vaccination differed by site, creating a quasi-experimental design.

RESULTS

Of 3181 participants, anti-HAV and anti-HBc seroprevalence was 19% and 23%, respectively. Although 83% of participants were willing to be vaccinated, only 36% received > or =1 dose, which varied by site: Baltimore (83%), Seattle (33%), Los Angeles (18%), New York (17%), and Chicago (2%). Participation was highest when vaccine was available immediately on-site and lowest when offered only after receiving results. Monetary incentives may have increased participation when on-site vaccination was not available.

CONCLUSION

IDUs were willing to be vaccinated but immediate, on-site availability was critical for uptake. Convenience should be a key consideration in designing strategies to increase vaccine coverage among IDUs.

Human immunity and the design of multi-component, single target vaccines

Background

Inclusion of multiple immunogens to target a single organism is a strategy being pursued for many experimental vaccines, especially where it is difficult to generate a strongly protective response from a single immunogen. Although there are many human vaccines that contain multiple defined immunogens, in almost every case each component targets a different pathogen. As a consequence, there is little practical experience for deciding where the increased complexity of vaccines with multiple defined immunogens vaccines targeting single pathogens will be justifiable.

Methodology/Principal Findings

A mathematical model, with immunogenicity parameters derived from a database of human responses to established vaccines, was used to predict the increase in the efficacy and the proportion of the population protected resulting from addition of further immunogens. The gains depended on the relative protection and the range of responses in the population to each immunogen and also to the correlation of the responses between immunogens. In most scenarios modeled, the gain in overall efficacy obtained by adding more immunogens was comparable to gains obtained from a single immunogen through the use of better formulations or adjuvants. Multi-component single target vaccines were more effective at decreasing the proportion of poor responders than increasing the overall efficacy of the vaccine in a population.

Conclusions/Significance

Inclusion of limited number of antigens in a vaccine aimed at targeting a single organism will increase efficacy, but the gains are relatively modest and for a practical vaccine there are constraints that are likely to limit multi-component single target vaccines to a small number of key antigens. The model predicts that this type of vaccine will be most useful where the critical issue is the reduction in proportion of poor responders.

Hepatitis A vaccines: the growing case for universal immunisation of children

Hepatitis A virus (HAV) infection results in a debilitating, multi-week illness in older children and adults that can be avoided with pre-exposure immunisation. Inactivated HAV vaccines are safe, highly effective and induce long-lasting protection. Immunisation has typically been recommended only for groups at highest risk of infection or complications, with variable success. This paper reviews the outcomes of several new programmes of universal HAV immunisation of children and/or adolescents. These programmes were associated with substantial disease rate reductions, extending beyond the immunised individuals and age groups (herd immunity), and promise additional benefits as immunised cohorts enter adulthood risk groups. Universal programmes are cost-effective, especially when a combined hepatitis A and B vaccine can be used to minimise incremental costs, and deserve wider consideration in developed countries.

Reactogenicity and immunogenicity profile of a two-dose combined hepatitis A and B vaccine in 1-11-year-old children

This study was conducted to compare the reactogenicity, immunogenicity and safety of a combined two-dose (0, 6 months) hepatitis A and B vaccine (720ELU HAV, 20 mcg HBsAg) with the established three-dose (0, 1 and 6 months) hepatitis A and B vaccine (360ELU HAV, 10 mcg HBsAg). A total of 511 children aged 1-11 years who had not previously received a hepatitis A or B vaccine were enrolled in the study. Both vaccines were well tolerated, and were shown to be safe and immunogenic. The analysis, stratified according to two age groups (1-5 year and 6-11-year-old children) demonstrated that the reactogenicity profile of the two-dose schedule was at least as good as that of the established schedule. Both vaccines and schedules provided at least 98% seroprotection against hepatitis B and 100% seroconversion against hepatitis A, 1 month after the end of the vaccination course (Month 7).

Immunogenicity of two paediatric doses of monovalent hepatitis B or combined hepatitis A and B vaccine in 8–10-year-old children

Hepatitis A and B vaccines are highly immunogenic in three-dose schedules. To obtain an equivalent result in children with two paediatric doses would be of significant benefit. The purpose of this study was to measure the immunogenicity of a two-dose schedule in children with two licensed recombinant HBsAg containing vaccines given at paediatric doses, one of them combined with hepatitis A. Seven-hundred and four healthy school children aged 8-10 years were recruited in an open label study to receive either Twinrix Pediatric (360 El.U HAV antigen; 10 microg HBsAg) or Recombivax (2.5 microg HBsAg) vaccine intramuscularly 6 months apart. The seroconversion (>/=1 mIU/ml for anti-HBs antibodies and >/=33 mIU/ml for anti-HAV antibodies), seroprotection (anti-HBs >/=10 mIU/ml) rates and the geometric mean titers (GMTs) were determined 4-8 weeks after the second dose. The anti-HBs seroconversion rate was 97.1% with Twinrix and 97.2% with Recombivax. The seroprotection rates were 96.5 and 94.4%, respectively (P = 0.17). The GMT was higher with Twinrix than with Recombivax (3248 mIU/ml versus 742 mIU/ml, P < 0.0001). All the children vaccinated with Twinrix seroconverted to HAV and the GMT was 5168 mIU/ml. The obtained results suggest that two paediatric doses of hepatitis vaccines are highly immunogenic in 8-10-year-old children. This schedule could facilitate a greater vaccine acceptance and the addition of hepatitis A vaccine to existing adolescent universal hepatitis B virus immunization programs.

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

Hepatitis A and B are two of the most common vaccine-preventable liver diseases and continue to be a significant cause of morbidity and mortality worldwide, with their severity related to the individual's age upon initial infection. Twinrix (GlaxoSmithKline), a combined vaccine providing protection against both hepatitis A and B, has been available in more than 72 countries worldwide since 1997. This paper provides a critical review of clinical data on the efficacy, immunogenicity and tolerability of the combined vaccine, with particular focus on the clinical benefits of dual vaccination.

A review of licensed viral vaccines, some of their safety concerns, and the advances in the development of investigational viral vaccines

Viral vaccines could be considered among the most important medical achievements of the 20th century. They have prevented much suffering and saved many lives. Although some curative antiviral drugs exist, we desperately depend on efforts by academic, governmental and industrial scientists in the advancement of viral vaccines in the prevention and control of infectious diseases. In the next decade, we hope to see advancement in the development of current and investigational viral vaccines against childhood and adult infections. In this article, we will review the licensed viral vaccines, some of their safety concerns, and the advances in the development of investigational viral vaccines.

Combined hepatitis A and B vaccines: a review of their immunogenicity and tolerability

Three combined hepatitis A and B vaccine preparations are commercially available in various countries: a two-dose paediatric formulation (Ambirix) [administered at months 0 and 6-12]; and a three-dose adult (Twinrix Adult) or paediatric (Twinrix Paediatric) formulation (administered at months 0, 1 and 6). The adult vaccine provides consistent, marked immunogenicity which is at least similar to that of its constituent vaccines used together and with a tolerability profile that is possibly improved. An accelerated, day-0, -7 and -21 regimen has also shown immunogenicity similar to that of the monovalent vaccines given concurrently, and now has an emerging role in adults likely to travel to hepatitis A virus (HAV) and/or hepatitis B virus (HBV) endemic regions within 1 month. The adult vaccine appears effective and generally well tolerated when given concurrently with monovalent typhoid vaccine (Typherix). Immunogenicity of the two-dose paediatric vaccine is high and appears to be similar whether administered as a month-0, -6 or month-0, -12 schedule and when compared to that of the three-dose paediatric vaccine (months 0, 1, 6), both of which provide a similar degree of protection to the adult vaccine. Although both preparations also provide high end-of-schedule seroprotection against hepatitis B surface antigen, protection between the first and second doses of the two-dose regimen appears lower than with the three-dose schedule. Therefore, the three-dose paediatric vaccine is a practical option in individuals at risk of immediate exposure to HBV, while the two-dose regimen may have an important function in immunisation programmes in regions where such risk is low. Combined hepatitis A and B vaccines are generally well tolerated. The most frequently reported adverse events in clinical trials were injection-site pain and redness, and general fatigue and headache; most events were mild and transient. Pharmacoeconomic models suggest the combined vaccine is cost effective compared with no vaccine (in children/adolescents) or monovalent hepatitis B vaccine (in children/adolescents and prison inmates).

CONCLUSION

The three commercially available combined hepatitis A and B adult and paediatric vaccines are highly immunogenic and generally well tolerated; the adult vaccine demonstrates immunogenicity at least as marked as that of monovalent hepatitis A and B vaccines. While further research is required to confirm potential advantages such as improved cost effectiveness, the combined vaccines have established a key role in the prevention of hepatitis A and B in defined risk groups, and have an expanding role in population-based vaccination programmes with younger age groups.

Hepatitis vaccines: recent advances

Despite the availability of hepatitis A vaccines that might provide protection for decades, hepatitis B vaccines that provides protection for at least 15 years and the recent introduction of a combined hepatitis A and B vaccine, these infections continue to spread in both the developed and developing world. Hepatitis A vaccine coverage has been limited to high-risk groups: such a selective immunisation policy is unlikely to have a major impact. If adequate immunogenicity in infants is confirmed, dosing schedules can be improved and the costs of vaccination reduced, universal paediatric immunisation with combined hepatitis A and B products is likely to result in the eventual eradication of these infections. In the interim, novel hepatitis A vaccines are being investigated and additional studies on hepatitis A vaccine immunogenicity in infants are in progress. Worldwide use of hepatitis B vaccines for the newborn, young children and high-risk groups should control this infection and obviate the need for a vaccine against hepatitis D. Newer hepatitis B vaccines that may reduce the likelihood of non-responsiveness and have immunotherapeutic value are under study. A recombinant hepatitis E vaccine for use in endemic regions is currently in clinical trials. The development of an effective hepatitis C vaccine has been agonisingly slow and many impediments have been recognised. These include the lack of a susceptible small animal, a high degree of hepatitis C virus (HCV) genomic diversity and failure to produce high quantities of HCV in tissue culture. The development of a novel HCV replicon system may be a major breakthrough. Nonetheless, it may still be exceedingly difficult to produce a vaccine that uniformly provides sterilising immunity; the possibility of developing a hepatitis C vaccine that can prevent chronic infection is an exciting concept that requires further investigation. Advances in recombinant technology, the use of novel genetic (DNA-based) vaccines, expression of hepatitis antigens in plants and improved adjuvants also hold considerable promise.

Combined two-dose hepatitis A and B vaccine (AmBirix)

One month after the last dose (i.e. at month 7), geometric mean titres (GMTs) of antibodies directed against hepatitis A virus (anti-HAV) were generally greater in participants (aged 12-15 years) receiving combined two-dose (0 and 6 months) hepatitis A and B vaccine (AmBirix) compared with the three-dose (containing one half the dose of the two active components per dose, given at 0, 1 and 6 months; Twinrix Paediatric) schedule. Moreover, at month 7 all patients had seroconverted to anti-HAV. GMTs of antibodies directed against hepatitis B surface antigen greatly exceeded the threshold for seroprotection (>/=10 mIU/mL) 1 month after the last dose of vaccine. Seroprotection rates against hepatitis B virus (HBV) were similar 1 month after completion of either a two- (97.9%) or three-dose (100%) vaccination schedule. At 24 months' follow-up, all patients tested remained positive for anti-HAV, and 93.3% and 96.2% of those treated with the two- and three-dose schedules, respectively, remained above the threshold for seroprotection against HBV. Administering the second dose in the two-dose series at 12 months rather than at 6 months did not compromise the immune response to the combined vaccine in adolescents aged 12-15 years in a randomised, multicentre trial. Local adverse events reported in the 4 days following administration of combined two-dose hepatitis A and B vaccine include pain or soreness, redness and swelling; systemic symptoms included headache, fatigue, gastrointestinal events and fever.

A novel hepatitis B vaccination regimen for adolescents: two doses 12 months apart

BACKGROUND

Two- and three-dose hepatitis B vaccinations for adolescents are usually administered using dosing schedules of 6 months duration. This does not suit all circumstances. A 12-month schedule would be useful in schools and settings where only annual vaccination is the most practical option.

AIM

To examine the efficacy of a 12-month dosing interval for two-dose hepatitis B vaccination of adolescents.

SUBJECTS

Four hundred and fifty-eight healthy first-year high school (Year 7) students. VACCINATION REGIMEN: Engerix-B (GlaxoSmithKline Biologicals) 20 micro g: two doses, 12 months apart. SERUM COLLECTION: #1, same day as first vaccine dose given; #2, >1 month after second vaccine dose.

RESULTS

Of the 458 children: 15 did not provide serum #1, 17 had prior vaccination, 2 had prior infection, 18 moved, 7 failed to provide serum #2, 12 withdrew (only 1 cited vaccine adverse reactions as the reason). Three hundred and eighty-seven (210 males, 177 females) aged 11.8-14.2 years (mean: 12.9+/-0.42 years) at entry completed both injections 321-381 days (mean: 359+/-10.7 days) apart and supplied serum #2, 30-57 days (mean: 41+/-5.6 days) after the second vaccine dose.Anti-HBs responses: 379 of the 387 subjects (97.9%; 95% CI: 95.9-99.1%) achieved anti-HBs > or =10 mIU/ml (range 10-170,460 mIU/ml, geometric mean concentration (GMC) 4155 mIU/ml-95% CI of mean: 3381-5106 mIU/ml). Sex was the only determinant of anti-HBs concentration (206 males: GMC 3073 mIU/ml-95% CI: 2285-4134 mIU/ml; 173 females: GMC 5944 mIU/ml-95% CI: 4508-7851 mIU/ml; P=0.001).

CONCLUSION

A high seroprotection rate and GMC were achieved using two 20 micro g doses of Engerix-B administered 12 months apart. These results are similar to those achieved by others using 6-month three- and two-dose regimens in adolescents.

Prevention of Viral Hepatitis

Despite the availability of vaccines against hepatitis A and B, acute viral hepatitis due to these agents continues to be among the most commonly reported notifiable infectious diseases in the United States. Currently available hepatitis A and B vaccines are highly immunogenic and well tolerated, but vaccine coverage needs to be expanded. Use of the hepatitis A vaccine in children age 2 years and older should be more widespread than is currently the case. Hepatitis A vaccine has been shown to be cost effective when given to children in regions with high attack rates and to patients with chronic hepatitis C. Routine newborn immunization against hepatitis B has been a successful approach to disease control and is among the most cost-effective interventions. Use of the hepatitis B vaccine for all sexually active individuals with more than one sex partner should be recommended for this sexually transmitted disease. The availability of a combined hepatitis A and B vaccine should facilitate vaccine coverage in those individuals at risk for both infections. For those hepatitis infections for which no vaccine is currently available, namely hepatitis C, D, and E, reducing exposure risk by modifying lifestyle behaviors is the only control measure available. Early education and counseling about high-risk behaviors for the acquisition of blood-borne hepatitis viruses needs to be expanded to young children and adolescents. The eventual eradication of hepatitis virus infections through universal immunization is plausible for those agents for whom human beings are the only host and effective vaccines have been developed. If hepatitis E is shown to be a zoonosis with an extensive reservoir in pigs, eradication of this agent may be very difficult.

Long term (24 months) follow-up of a hepatitis A and B vaccine, comparing a two and three dose schedule in adolescents aged 12-15 years

BACKGROUND

A two dose schedule (0 and 6 months) for a combined hepatitis A and B vaccine is currently being developed.

METHODS

The present study compared the combined hepatitis A and B vaccines in 12-15-year-old: Twinrix paediatric (360 EL.U HAV antigen/10 microg HBs antigen) on a three dose schedule (0, 1 and 6 months) to the adult formulation (720 EL.U HAV antigen/20 microg HBs antigen) on a two dose schedule (0 and 6 months) and also reports on the follow-up until 24 months.

RESULTS

Seroconversion (SC) rates to HAV in both regimens reached 100% by month 7 and remained 100% up to month 24. Anti-HAV, GMTs were slightly higher for the two dose than the three dose regimens at this time point. Seroprotection against hepatitis B was >99% in both groups by month 7 and 24, this was still 94 and 96%, respectively. Statistical non-inferiority of group 1 (two dose) versus group 2 (three dose) was demonstrated. All vaccines were well tolerated and the most frequently reported local and general symptoms were pain and fatigue. There were no vaccine-related serious adverse events reported during the study.

CONCLUSION

The two dose regimen elicited similar immunogenicity to HAV and HBsAg and reactogenicity profiles as the three dose regimen in this group of healthy adolescents. The reduction in the number of doses from the current three dose schedule will make vaccination against hepatitis A and B more convenient to the vaccinee, reduce healthcare staff time required and may lower the overall costs associated with vaccination.