Can monovalent hepatitis A and B vaccines be replaced by a combined hepatitis A/B vaccine during the primary immunization course?

[Baby on board - recommendations for pediatric travel consultation]

Traveling with babies and children is challenging for parents and the doctor providing travel medicine advice. Especially pediatric VFR (visiting friends and relatives) travelers have a higher risk for infectious diseases due to lower risk perception and higher exposure. Being well prepared helps in exploring the world while staying healthy. Topics to be discussed in pediatric travel consultation are travel vaccinations, mosquito repellents, malaria prophylaxis, thorough sun protection, rehydration for gastroentritis, avoidance of rabies exposure, an agetailored travel pharmacy and more. We provide a guide to the most important topics for pediatric travel consultations.

Transcriptomic profiling of different responder types in adults after a Priorix® vaccination

Thanks to the recommendation of a combined Measles/Mumps/Rubella (MMR) vaccine, like Priorix®, these childhood diseases are less common now. This is beneficial to limit the spread of these diseases and work towards their elimination. However, the measles, mumps and rubella antibody titers show a large variability in short- and long-term immunity. The recent outbreaks worldwide of measles and mumps and previous studies, which mostly focused on only one of the three virus responses, illustrate that there is a clear need for better understanding the immune responses after vaccination. Our healthy cohort was already primed with the MMR antigens in their childhood. In this study, the adult volunteers received one Priorix® vaccine dose at day 0. First, we defined 4 different groups of responders, based on their antibody titers' evolution over 4 time points (Day 0, 21, 150 and 365). This showed a high variability within and between individuals. Second, we determined transcriptome profiles using 3'mRNA sequencing at day 0, 3 and 7. Using two analytical approaches, "one response group per time point" and "a time comparison per response group", we correlated the short-term gene expression profiles to the different response groups. In general, the list of differentially expressed genes is limited, however, most of them are clearly immune-related and upregulated at day 3 and 7, compared to the baseline day 0. Depending on the specific response group there are overlapping signatures for two of the three viruses. Antibody titers and transcriptomics data showed that an additional Priorix vaccination does not facilitate an equal immune response against the 3 viruses or among different vaccine recipients.

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.

Immunogenicity and safety of concomitant administration of a combined hepatitis A/B vaccine and a quadrivalent meningococcal conjugate vaccine in healthy adults

BACKGROUND

This phase 3b randomized, open-label study evaluated the immunogenicity and safety of coadministration of a hepatitis A and/or B vaccine with a quadrivalent oligosaccharide meningococcal CRM197 -conjugate vaccine (MenACWY-CRM), in the context of an accelerated hepatitis A and/or B immunization schedule.

METHODS

A total of 252 healthy adult subjects were randomized to three groups to receive hepatitis A/B only (HepA/B), hepatitis A/B coadministered with MenACWY-CRM (HepA/B+MenACWY-CRM), or MenACWY-CRM only (MenACWY-CRM). Hepatitis A and/or B vaccination was administered in the form of a single booster dose or a primary three-dose series, depending on the hepatitis A and/or B vaccination history of subjects. Antibody responses to hepatitis A/B vaccination were assessed 1 month following the last hepatitis A and/or B dose. Serum bactericidal activity with human complement (hSBA) against meningococcal serogroups A, C, W-135, and Y was assessed 1 month post-MenACWY-CRM vaccination. Safety was monitored throughout the study.

RESULTS

At 1 month following the final hepatitis A and/or B vaccination, concomitant administration of hepatitis A/B and MenACWY-CRM was non-inferior to administration of hepatitis A/B alone in terms of geometric mean concentrations of antibodies against the hepatitis A and B antigens. One month post-MenACWY-CRM vaccination, the percentages of subjects achieving hSBA titers ≥8 for serogroups A, C, W-135, and Y in the HepA/B+MenACWY-CRM group (76, 87, 99, and 94%, respectively) were comparable to those in the MenACWY-CRM group (67, 82, 96, and 88%, respectively). The percentages of subjects reporting adverse events (AEs) were similar across study groups and a majority of the reported AEs were mild to moderate in nature. There were no study vaccine-related serious AEs.

CONCLUSIONS

MenACWY-CRM can be administered concomitantly with a hepatitis A and/or B vaccine in the context of an accelerated hepatitis A and/or B immunization schedule without increasing safety concerns or compromising the immune responses to any of the vaccine antigens. [NCT01453348].

Effects of varying antigens and adjuvant systems on the immunogenicity and safety of investigational tetravalent human oncogenic papillomavirus vaccines: results from two randomized trials

BACKGROUND

A prophylactic human papillomavirus (HPV) vaccine targeting oncogenic HPV types in addition to HPV-16 and -18 may broaden protection against cervical cancer. Two Phase I/II, randomized, controlled studies were conducted to compare the immunogenicity and safety of investigational tetravalent HPV L1 virus-like particle (VLP) vaccines, containing VLPs from two additional oncogenic genotypes, with the licensed HPV-16/18 AS04-adjuvanted vaccine (control) in healthy 18-25 year-old women.

METHODS

In one trial (NCT00231413), subjects received control or one of 6 tetravalent HPV-16/18/31/45 AS04 vaccine formulations at months (M) 0,1,6. In a second trial (NCT00478621), subjects received control or one of 5 tetravalent HPV-16/18/33/58 vaccines formulated with different adjuvant systems (AS04, AS01 or AS02), administered on different schedules (M0,1,6 or M0,3 or M0,6).

RESULTS

One month after the third injection (Month 7), there was a consistent trend for lower anti-HPV-16 and -18 geometric mean antibody titers (GMTs) for tetravalent AS04-adjuvanted vaccines compared with control. GMTs were statistically significantly lower for an HPV-16/18/31/45 AS04 vaccine containing 20/20/10/10 μg VLPs for both anti-HPV-16 and anti-HPV-18 antibodies, and for an HPV-16/18/33/58 AS04 vaccine containing 20/20/20/20 μg VLPs for anti-HPV-16 antibodies. There was also a trend for lower HPV-16 and -18-specific memory B-cell responses for tetravalent AS04 vaccines versus control. No such trends were observed for CD4(+) T-cell responses. Immune interference could not always be overcome by increasing the dose of HPV-16/18 L1 VLPs or by using a different adjuvant system. All formulations had acceptable reactogenicity and safety profiles. Reactogenicity in the 7-day post-vaccination period tended to increase with the introduction of additional VLPs, especially for formulations containing AS01.

CONCLUSIONS

HPV-16 and -18 antibody responses were lower when additional HPV L1 VLPs were added to the HPV-16/18 AS04-adjuvanted vaccine. Immune interference is a complex phenomenon that cannot always be overcome by changing the antigen dose or adjuvant system.

Hepatitis A immunity in the District of Aveiro (Portugal): an eleven-year surveillance study (2002-2012)

Hepatitis A is a common viral liver disease and brings serious health and economic problems as its epidemiologic pattern changes over time. National serosurveys from developed countries have indicated a decline in HAV (hepatitis A virus) seroprevalence over time due to the improvement of economic and sanitation levels. The hepatitis A virus (HAV) immunity rate was surveyed throughout an eleven-year period by sex and age group in Aveiro District. In this retrospective study, blood samples from patients of Aveiro District, in ambulatory regime, collected at the Clinical Analysis Laboratory Avelab between 2002 and 2012 were screened for the presence of antibodies against HAV antigen using a chemiluminescence immunoassay. The global immunity (positive total anti-HAV) was 60% and only 0.3% of the patients presented recent infection by HAV (positive IgM anti-HAV). The HAV immunity was age-dependent (p < 0.05), but no significant differences (p > 0.05) between sexes were observed. The immunity was similar throughout the study period (p > 0.05). The results of this study indicate that young people (especially under 25 years old) from District of Aveiro are susceptible to HAV infection, constituting a high risk group. The elderly should be also a concern in the future of Hepatitis A infection.

Business travelers: vaccination considerations for this population

Illness in business travelers is associated with reduced productivity on the part of the employee as well as the employer. Immunizations offer a reliable method of preventing infectious diseases for international business travelers. The authors review the travel patterns of business travelers, available data on illnesses they encounter, their potential travel-associated risks for vaccine-preventable diseases and recommendations on immunizations for this population. Routine vaccines (e.g., measles, tetanus and influenza) should be reviewed to assure that they provide current coverage. The combined hepatitis A and hepatitis B vaccine with a rapid schedule offers options for those with time constraints. Other vaccine recommendations for business travelers need to focus on their destinations and activities and underlying health, taking into account the concept of cumulative risk for those with frequent travel, multiple trips or long stays.

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.

Vaccination of travelers: how far have we come and where are we going?

Vaccine recommendations are a prominent part of health preparations before international travel. We review progress made in the past decade regarding vaccines used primarily by persons traveling from high-income countries to low- and middle-income countries. The combined hepatitis A-B vaccine, the recently licensed Vero cell-derived Japanese encephalitis vaccine and conjugated quadrivalent meningococcal vaccines are discussed. This article provides updates on yellow fever vaccine-associated visceral and neurologic adverse events, indications for influenza vaccine in travelers, the rapid immunization schedule for tick-borne encephalitis vaccine, schedules for postexposure rabies prophylaxis, and new insights about oral cholera vaccines following the outbreak in Haiti. The future should bring vaccines for serogroup B Neiserria meningitidis, dengue and malaria, as well as an inactivated yellow fever vaccine.

Use of an accelerated immunization schedule for combined hepatitis A and B protection in the corporate traveler

Increased international business travel to moderate or high endemic areas of hepatitis A and B may leave many business travelers at risk for infection if not vaccinated. Many international business travelers depart for hepatitis A and B endemic areas within 2 months of the decision to travel. Many of these travelers do not seek pretravel medical advice and are unaware of the risks and modes of acquiring hepatitis A and B. Monovalent vaccines and a combined hepatitis A and B vaccine are available and can be administered on an accelerated schedule. Because many areas endemic for hepatitis A are also endemic for hepatitis B, accelerated administration of the combined vaccine can offer protection for many international business travelers destined for areas endemic for both diseases and should be part of corporate travel immunization programs.

The underestimated risk of hepatitis A and hepatitis B: benefits of an accelerated vaccination schedule

Hepatitis A virus (HAV) and hepatitis B virus (HBV) are vaccine-preventable. Current recommendations advocate vaccination of non-immune adults at risk of exposure, including travelers to HAV or HBV endemic areas, individuals with high risk of contracting a sexually transmitted infection, and some correctional facility inmates. We review the use of an accelerated schedule to administer the combination hepatitis A and hepatitis B vaccine (Twinrix). Administering three doses over three weeks and a fourth at 12 months provides rapid initial protection of most individuals for whom the standard 6-month vaccination schedule would not be suitable, including last-minute travelers and short-term correctional facility inmates. Furthermore, we consider the role of a universal vaccination strategy in preventing the spread of HAV and HBV.

Rapid and sustained immune response against hepatitis A and B achieved with combined vaccine using an accelerated administration schedule

BACKGROUND

Combined hepatitis A and B vaccine administered on an accelerated schedule provides a rapid immune response against both hepatitis A and B viruses, which might be especially relevant for individuals who need protection quickly.

METHODS

A prospective, open-label, randomized study to compare the immunogenicity and reactogenicity of the combined hepatitis A and B vaccine Twinrix (GlaxoSmithKline Biologicals, Rixensart, Belgium) (>or=720 EL.U/mL inactivated hepatitis A antigen and 20 microg/mL recombinant hepatitis B surface antigen [HBsAg]) administered at 0, 7, 21 to 30 days, and 12 months compared with concurrent administration of Havrix [GlaxoSmithKline Biologicals, Rixensart, Belgium (>or=1440 EL.U/mL inactivated hepatitis A antigen)] at 0 and 12 months, and Engerix-B [GlaxoSmithKline Biologicals, Rixensart, Belgium (20 microg/mL recombinant HBsAg)] at 0, 1, 2, and 12 months in seronegative healthy adults.

RESULTS

At month 13, the anti-hepatitis B seroprotection rates (>10 mIU/mL) for the combined vaccine compared to the monovalent hepatitis B vaccine were 96.4% (95% CI: 92.7-98.5) and 93.4% (95% CI: 89.0-96.4), respectively. The anti-hepatitis A seroconversion rates were 100% in both groups (95% CI: 98.1-100). At day 37, the anti-hepatitis A seroconversion rates were similar in both groups (98.5% for combined vaccine, 98.6% for the monovalent vaccine group), but the combined vaccine resulted in a statistically significantly ( p < 0.001) better anti-hepatitis B seroprotection compared to monovalent hepatitis B vaccine, 63.2% versus 43.5%, respectively. The reactogenicity profile was similar in both study groups.

CONCLUSIONS

The combined hepatitis A and B vaccine administered on an accelerated schedule was at least as immunogenic and as well tolerated as the corresponding monovalent vaccines.

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.

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.

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.

Prevalence of hepatitis A antibodies in schoolchildren in Catalonia (Spain) after the introduction of universal hepatitis A immunization

The objective of this study was to investigate the prevalence of hepatitis A antibodies (anti-HAV) in schoolchildren in Catalonia and to compare it with the rates found in previous studies. Sera from a representative sample of 1,342 children aged between 6 and 15 years, recruited in 2001, were tested for anti-HAV. The results were related to sociodemographic variables and vaccination history. The overall prevalence of anti-HAV was 51.4%. The prevalence was 5.5% in non-vaccinated children, similar to that found in a 1996 study, and 96.6% in vaccinated children. The prevalence of anti-HAV in non-vaccinated children increased significantly with age, reaching 11.6% in the 13-15 years age group. The prevalence of anti-HAV was higher in children born outside Catalonia than in those born in Catalonia (16.1% vs. 5.0%, P = 0.02). The expected continuation in the decline in the prevalence of anti-HAV in non-vaccinated schoolchildren, observed in Catalonia since 1986, was not found in 2001. The rate of anti-HAV in 2001 was slightly higher than in 1996, although the difference was not statistically significant (5.5 and 3.5%, respectively). This could be explained by the increased number of recent immigrant children born outside Catalonia, mainly in countries where hepatitis A is highly endemic.

Hepatitis A booster vaccination: is there a need?

Hepatitis A is one of the most common vaccine-preventable infectious diseases in the world. Effective vaccines against hepatitis A have been available since 1992, and they provide long-term immunity against the infection. However, there is no worldwide consensus on how long protection will last or whether there will be a need for hepatitis A virus (HAV) booster vaccinations in the future. In most countries, booster-vaccination policy is guided by manufacturers' recommendations, national authorities, or both. In June, 2002, a panel of international experts met to review the long-term immunogenicity and protection conferred by HAV vaccine in different population groups. Data have shown that after a full primary vaccination course, protective antibody amounts persist beyond 10 years in healthy individuals, and underlying immune memory provides protection far beyond the duration of anti-HAV antibodies. The group concluded that there is no evidence to lend support to HAV booster vaccination after a full primary vaccination course in a healthy individual. However, further investigations are needed before deciding if boosters can be omitted in special patient-groups.

When can a clinical trial be called 'randomized'?

It is widely recognized that, in the context of the evaluation of medical interventions, randomized clinical trials constitute the gold standard. This is because randomization tends to balance both measured and unmeasured baseline characteristics, allows for masking, and provides a basis for inference. It is understandable, then, that investigators would wish to utilize this methodology whenever it is feasible to do so. Unfortunately, some studies are labeled as randomized when in fact they are not. These studies then receive more credibility, and influence medical practice, more than they deserve to. After reviewing the benefits of randomization, paying particular attention to the specific aspects of randomization that confer each benefit, we will explore the issue of what constitutes a randomized study.

Recent Advances and New Challenges in Travel Medicine

Recent advances in travel medicine include the use of computer resources to obtain information on outbreaks and recommendations to travelers, the introduction of atovaquone/proguanil as chemoprophylaxis and treatment for malaria, the use of azithromycin as an alternative in the self-treatment of traveler's diarrhea, and the combination of hepatitis A and hepatitis B vaccines. At the same time, new challenges continue to appear. Shifts in the distribution of infections, such as West Nile virus and dengue fever, underscore the need for up-to-date information. Well-known infectious diseases, such as polio, meningococcal meningitis, and influenza are appearing in unexpected ways and settings. It is increasingly clear that travelers, while at risk for infections, also play a role in the global dispersal of pathogens, such as certain serogroups of Neisseria meningitidis and influenza. Increasing drug resistance affects the choice of drugs for treatment and chemoprophylaxis, and decisions about use of vaccines. Newly identified adverse events associated with yellow fever vaccine have prompted enhanced surveillance after vaccination and careful scrutiny of appropriate indications for the vaccine.

A two-dose combined vaccine against hepatitis A and hepatitis B in healthy children and adolescents compared to the corresponding monovalent vaccines

BACKGROUND

Immunization against hepatitis A and B has been available for some time, protecting against both infections. With a view to achieving further reduction in the number of interventions and increasing convenience of the vaccinee, we investigated the reactogenicity and immunogenicity of a combined hepatitis A and B vaccine in healthy 4- to 20-year-old subjects at a 0, 6-month schedule.

METHODS

Two hundred forty-eight study subjects were allocated to two study groups and received either two doses of the combined hepatitis A and B vaccine (68% of subjects) or the corresponding monovalent hepatitis A and hepatitis B vaccines (32% of subjects) concomitantly in opposite arms. Reactogenicity was assessed via diary cards after each vaccination. Serum samples were analyzed at months 1, 2, 6, and 7.

RESULTS

All vaccines were well tolerated and very few symptoms were scored as severe. All but one subject seroconverted for anti-hepatitis A virus (anti-HAV) antibodies (98.6%) and 100% of subjects seroconverted for anti-hepatitis B (HBs) antibodies, with respective seroprotection rates of 98.7% for the combined vaccine group and 95.9% for the concomitant vaccine group (p >0.05), respectively. Geometric mean titers were higher in the group receiving the combined vaccine: 6,635 mIU/mL vs. 2,728 mIU/mL (p = 0.0001) for anti-HAV and 3,362 mIU/mL vs. 1,724 mIU/mL (p = 0.0205) for anti-HBs, respectively. Younger subjects had a stronger immune response compared to older subjects.

CONCLUSIONS

The combined hepatitis A and B vaccine was well tolerated at this two-dose schedule. The combined vaccine had higher immunogenicity, probably explained by a adjuvant effect of the antigens. Vaccination programs requiring fewer injections will most likely have a positive impact on compliance rate and comfort of the vaccinee.

Magnitude and quality of antibody response to a combination hepatitis A and hepatitis B vaccine

Interference between antibodies generated by a combination hepatitis A and B vaccine was investigated by evaluating the quantity and quality of anti-hepatitis A virus (HAV) and anti-hepatitis B surface antigen (HBs) antibodies generated by Twinrix (Hepatitis A Inactivated and Hepatitis B (Recombinant) Vaccine). The magnitude of the immune response was determined by a retrospective analysis of eight clinical trials, completed during stepwise development of Twinrix. The functionality of anti-HAV was evaluated by comparison of routine ELISA results with neutralization assays and was further characterized by defining the epitope-specificity of binding. Functionality of the anti-HBs response was not tested because a validated assay was not developed at the time this study was conducted. Results of all analyses demonstrated that the combination vaccine induced high antibody titers against hepatitis A and B and a functional anti-HAV response, with no evidence of immune interference to either viral antigen.