Interference of antibody production to hepatitis B surface antigen in a combination hepatitis A/hepatitis B vaccine

HBV Vaccines: Advances and Development

Hepatitis B virus (HBV) infection is a global public health problem that is closely related to liver cirrhosis and hepatocellular carcinoma (HCC). The prevalence of acute and chronic HBV infection, liver cirrhosis, and HCC has significantly decreased as a result of the introduction of universal HBV vaccination programs. The first hepatitis B vaccine approved was developed by purifying the hepatitis B surface antigen (HBsAg) from the plasma of asymptomatic HBsAg carriers. Subsequently, recombinant DNA technology led to the development of the recombinant hepatitis B vaccine. Although there are already several licensed vaccines available for HBV infection, continuous research is essential to develop even more effective vaccines. Prophylactic hepatitis B vaccination has been important in the prevention of hepatitis B because it has effectively produced protective immunity against hepatitis B viral infection. Prophylactic vaccines only need to provoke neutralizing antibodies directed against the HBV envelop proteins, whereas therapeutic vaccines are most likely needed to induce a comprehensive T cell response and thus, should include other HBV antigens, such as HBV core and polymerase. The existing vaccines have proven to be highly effective in preventing HBV infection, but ongoing research aims to improve their efficacy, duration of protection, and accessibility. The routine administration of the HBV vaccine is safe and well-tolerated worldwide. The purpose of this type of immunization is to trigger an immunological response in the host, which will halt HBV replication. The clinical efficacy and safety of the HBV vaccine are affected by a number of immunological and clinical factors. However, this success is now in jeopardy due to the breakthrough infections caused by HBV variants with mutations in the S gene, high viral loads, and virus-induced immunosuppression. In this review, we describe various types of available HBV vaccines, along with the recent progress in the ongoing battle to develop new vaccines against HBV.

Immunogenicity of Multi-Target Chimeric RHDV Virus-like Particles Delivering Foreign B-Cell Epitopes

The rabbit hemorrhagic disease virus (RHDV) vaccine platform is a nanoparticle composed of 180 copies of the viral capsid protein, VP60, self-assembled into virus-like particles (VLPs). RHDV VLPs are able to accept the simultaneous incorporation of target epitopes at different insertion sites. The resulting chimeric RHDV VLPs displaying immunogenic foreign antigens have been shown to induce specific protective immune responses against inserted heterologous T-cytotoxic and B-cell epitopes in the mouse and pig models. In this study, we explored whether RHDV-based engineered VLPs can be developed as efficient multivalent vaccines co-delivering different foreign B-cell antigens. We generated bivalent chimeric RHDV VLPs displaying two model B-cell epitopes at different surface-exposed insertion sites, as well as the corresponding monovalent chimeric VLPs. The immunogenic potential of the bivalent chimeric VLPs versus the monovalent constructs was assessed in the mouse model. We found that the bivalent chimeric VLPs elicited a strong and balanced antibody response towards the two target epitopes tested, although slight reductions were observed in the levels of specific serum antibody titers induced by bivalent chimeric VLPs as compared with the corresponding monovalent constructs. These results suggest that RHDV VLPs could represent a promising platform for the development of efficient multivalent vaccines.

Immunogenicity of Viral Vaccines in the Italian Military

Military personnel of all armed forces receive multiple vaccinations and have been doing so since long ago, but relatively few studies have investigated the possible negative or positive interference of simultaneous vaccinations. As a contribution to fill this gap, we analyzed the response to the live trivalent measles/mumps/rubella (MMR), the inactivated hepatitis A virus (HAV), the inactivated trivalent polio, and the trivalent subunits influenza vaccines in two cohorts of Italian military personnel. The first cohort was represented by 108 students from military schools and the second by 72 soldiers engaged in a nine-month mission abroad. MMR and HAV vaccines had never been administered before, whereas inactivated polio was administered to adults primed at infancy with a live trivalent oral polio vaccine. Accordingly, nearly all subjects had baseline antibodies to polio types 1 and 3, but unexpectedly, anti-measles/-mumps/-rubella antibodies were present in 82%, 82%, and 73.5% of subjects, respectively (43% for all of the antigens). Finally, anti-HAV antibodies were detectable in 14% and anti-influenza (H1/H3/B) in 18% of the study population. At mine months post-vaccination, 92% of subjects had protective antibody levels for all MMR antigens, 96% for HAV, 69% for the three influenza antigens, and 100% for polio types 1 and 3. An inverse relationship between baseline and post-vaccination antibody levels was noticed with all the vaccines. An excellent vaccine immunogenicity, a calculated long antibody persistence, and apparent lack of vaccine interference were observed.

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.

Chimeric GII.4 norovirus virus-like-particle-based vaccines induce broadly blocking immune responses

There is currently no licensed vaccine for noroviruses, and development is hindered, in part, by an incomplete understanding of the host adaptive immune response to these highly heterogeneous viruses and rapid GII.4 norovirus molecular evolution. Emergence of a new predominant GII.4 norovirus strain occurs every 2 to 4 years. To address the problem of GII.4 antigenic variation, we tested the hypothesis that chimeric virus-like particle (VLP)-based vaccine platforms, which incorporate antigenic determinants from multiple strains into a single genetic background, will elicit a broader immune response against contemporary and emergent strains. Here, we compare the immune response generated by chimeric VLPs to that of parental strains and a multivalent VLP cocktail. Results demonstrate that chimeric VLPs induce a more broadly cross-blocking immune response than single parental VLPs and a similar response to a multivalent GII.4 VLP cocktail. Furthermore, we show that incorporating epitope site A alone from one strain into the background of another is sufficient to induce a blockade response against the strain donating epitope site A. This suggests a mechanism by which population-wide surveillance of mutations in a single epitope could be used to evaluate antigenic changes in order to identify potential emergent strains and quickly reformulate vaccines against future epidemic strains as they emerge in human populations.

IMPORTANCE

Noroviruses are gastrointestinal pathogens that infect an estimated 21 million people per year in the United States alone. GII.4 noroviruses account for >70% of all outbreaks, making them the most clinically important genotype. GII.4 noroviruses undergo a pattern of epochal evolution, resulting in the emergence of new strains with altered antigenicity over time, complicating vaccine design. This work is relevant to norovirus vaccine design as it demonstrates the potential for development of a chimeric VLP-based vaccine platform that may broaden the protective response against multiple GII.4 strains and proposes a potential reformulation strategy to control newly emergent strains in the human population.

Protective efficacy and immunogenicity of a combinatory DNA vaccine against Influenza A Virus and the Respiratory Syncytial Virus

The Respiratory Syncytial Virus (RSV) and Influenza A Virus (IAV) are both two major causative agents of severe respiratory tract infections in humans leading to hospitalization and thousands of deaths each year. In this study, we evaluated the immunogenicity and efficacy of a combinatory DNA vaccine in comparison to the single component vaccines against both diseases in a mouse model. Intramuscular electroporation with plasmids expressing the hemagglutinin (HA) of IAV and the F protein of RSV induced strong humoral immune responses regardless if they were delivered in combination or alone. In consequence, high neutralizing antibody titers were detected, which conferred protection against a lethal challenge with IAV. Furthermore, the viral load in the lungs after a RSV infection could be dramatically reduced in vaccinated mice. Concurrently, substantial amounts of antigen-specific, polyfunctional CD8⁺ T-cells were measured after vaccination. Interestingly, the cellular response to the hemagglutinin was significantly reduced in the presence of the RSV-F encoding plasmid, but not vice versa. Although these results indicate a suppressive effect of the RSV-F protein, the protective efficacy of the combinatory vaccine was comparable to the efficacy of both single-component vaccines. In conclusion, the novel combinatory vaccine against RSV and IAV may have great potential to reduce the rate of severe respiratory tract infections in humans without increasing the number of necessary vaccinations.

Reovirus inhibits poliovirus replication upon superinfection

OBJECTIVE

Viral interference has been demonstrated in different systems, such as the effect of enterovirus infection on live-attenuated oral polio vaccine. In this study, the effect of reovirus which could exist in the human intestinal tract on poliovirus vaccine strains was investigated and could be an important factor to consider in oral polio vaccination.

METHODS

Cells were infected with reovirus, then superinfected with poliovirus. The amount of viral yields was measured by the TCID(50) and plaque assay methods. Polioviral RNA synthesis was studied by real-time RT-PCR and the viral RNA load was calculated. Viral protein synthesis was determined using the techniques of immunoflourescent staining and PAGE followed by the immunoblotting experiment.

RESULTS

Poliovirus superinfection of reovirus-infected cells resulted in inhibition of poliovirus replication. It was found that the inhibitory effect of reovirus was after establishment of its infection (2 h postinfection). There was no competition between the two viruses for cell attachment but poliovirus RNA and protein synthesis were inhibited.

CONCLUSION

Infection of cells with reovirus could interfere with the growth of poliovirus upon superinfection. This phenomenon could be important to consider when using attenuated poliovirus vaccine.

Characterization and immune effect of the hepatitis B-BCG combined vaccine for using a needle innoculation

OBJECTIVE

To prepare the hepatitis B-Mycobacterium bovis Bacillus Calmette-Guérin combined vaccine (HB-BCG combined vaccine) and resolve a needle problem of the two kinds of hepatitis B vaccine (HB vaccine) and M. bovis Bacillus Calmette-Guérin (BCG) for the innoculation.

METHODS

The hepatitis B surface antigen (HBsAg) was prepared by the genetic engineering technique, BCG was produced using routine biological technique, and then the finished products of the HB-BCG combined vaccine were processed on the above foundation. The content of HBsAg was measured by Enzyme linked immunosorbent assay (ELISA), the immune effect of BCG was detected by purified protein derivative (PPD) test. Cellular immune response, safety, partial poison and allergy were tested. The stability of HB-BCG combined vaccine was detected by ELISA and viable count method.

RESULTS

The two kinds of antigens (HBsAg and BCG) had good compatibility. The comparison on immune effects of HB-BCG combined vaccine and BCG showed no significant difference. The comparison on immune effects of HB-BCG combined vaccine group (first dose for HB-BCG Combined vaccine, second and third dose for HB vaccine) and HB vaccine group (three dose all for HB vaccine) demonstrated that anti-HBs levels of the HB-BCG combined vaccine group were higher than that of HB vaccine group. No statistical significance was observed between the combined vaccine group and HB vaccine group after three doses immunization schedules. The results of safety in HB-BCG combined vaccine group accorded with that of BCG group, it had been not found the pathological changes of the tuberculosis. The characteristic and process in pathological changes of HB-BCG combined vaccine group and BCG group were similar in the partial poison test. HBsAg did not strengthen the inflammation reaction caused by BCG. Systemic allergy had not been found. The HB-BCG combined vaccine was stable in 2 years.

CONCLUSION

The immune effects of the HB-BCG combined vaccine were not lower than the two kinds of single dose vaccine, it had good safety.

Swine influenza matrix 2 (M2) protein contributes to protection against infection with different H1 swine influenza virus (SIV) isolates

A swine influenza virus (SIV) vaccine-challenge pig model was used to study the potential of a conserved matrix 2 (M2) protein vaccine alone or in combination with an inactivated H1N1-vaccine to protect against H1N1 and H1N2 viruses. The H1N1-vaccine and heterologous H1N2-challenge virus model has previously been shown to prolong fever and increase SIV-associated pneumonic lesions. The M2 vaccine in combination with the H1N1-vaccine reduced the H1N2 induced fever but not virus shedding. The M2 vaccine alone reduced respiratory signs and pneumonic lesions to levels similar to the negative control pigs following H1N2 infection. This study found that the M2 protein has potential as a vaccine for SIV-associated disease prevention. However, development of an immune response towards the major envelope HA protein was required to reduce SIV shedding.

A review of multiple approaches towards an improved hepatitis B vaccine

BACKGROUND

Hepatitis B is a DNA virus that can cause liver inflammation, cirrhosis, and cancer in chronically infected and symptomatic carriers. Antiviral treatments are usually limited in their effectiveness in treating the disease states. Vaccination against hepatitis B in pediatric and adolescent populations has proven to be a generally effective means for preventing diseases that could be potentially caused by this virus. Some 5 - 10% of the vaccinees do not develop protective immunity against the virus. Therefore, a significant amount of effort has been made in many research laboratories across the world to increase the potency of the vaccine by various innovative means, e.g., increasing the immunogenicity of the antigen or through introduction of novel adjuvants that elicit strong humoral and cell-mediated immune responses.

OBJECTIVES/METHODS

The objective of this review is to highlight publications of significant developments that have been made over the past decade and efforts that are continuing towards producing an improved vaccine. A number of patents that protect novel hepatitis B vaccine formulations, including those claiming novel hepatitis B core antigen formulations and combinations of a vaccine with small molecule therapeutics, are discussed.

CONCLUSION

There have been promising developments in the area of new adjuvants and delivery systems. The practical need for reducing the total number of childhood vaccinations has driven development of, and patent filings on, multivalent and combination vaccine formulations in which the hepatitis B vaccine is included as one component. Efforts and some advances have also been made in the critical area of therapeutic application of the vaccine. The existence of a large population of already infected patients and the inadequacy of most of the current antiviral drugs against hepatitis B diseases have also inspired efforts to produce a vaccine that would be efficacious in clearing an exiting infection.

Evaluation of combinatorial vaccines against anthrax and plague in a murine model

In this study, we examine the potential of a combinatorial vaccine consisting of the lead-candidate antigens for the next generations of vaccines against anthrax (rPA) and plague (F1-V) with the specific objective of determining synergy or interference between the vaccine components when they are administered separately or together by both traditional parenteral immunization (SC) and mucosal immunization (IN) in the presence of appropriate adjuvants. The most significant findings of the study reported here are that (1) a combinatorial vaccine consisting of equal amounts of F1-V and rPA administered SC is effective at eliciting a robust serum and bronchoalveolar lavage (BAL) antigen-specific IgG and IgG1 response against both antigens in immunized animals, and when administered IN, a robust antigen-specific IgG2a response in the serum and BAL is also induced; (2) there were few instances where either synergy or interference was observed in the combined vaccine administered by either route and those differences occurred soon after the final immunization and were not sustained over time; (3) IN immunization was as effective as SC immunization for induction of antigen-specific serum and BAL antibody responses using the same amount of antigen; (4) the IgG1/IgG2a ratios suggest a strongly biased Type 2 response following SC immunization, while IN immunization produced a more balanced Type 1/Type 2 response; (5) the IgG1/IgG2a ratio was influenced by the route of immunization, the adjuvant employed, and the nature of the antigen. As with previously published studies, there were still detectable levels of circulating anti-F1-V and anti-rPA even 6 months post-primary immunization. These studies provide important insights into the development of new generation biodefense vaccines.

Statistical considerations for noninferiority/equivalence trials in vaccine development

Noninferioritylequivalence designs are often used in vaccine clinical trials. The goal of these designs is to demonstrate that a new vaccine, or new formulation or regimen of an existing vaccine, is similar in terms of effectiveness to the existing vaccine, while offering such advantages as easier manufacturing, easier administration, lower cost, or improved safety profile. These noninferioritylequivalence designs are particularly useful in four common types of immunogenicity trials: vaccine bridging trials, combination vaccine trials, vaccine concomitant use trials, and vaccine consistency lot trials. In this paper, we give an overview of the key statistical issues and recent developments for noninferioritylequivalence vaccine trials. Specifically, we cover the following topics: (i) selection of study endpoints; (ii) formulation of the null and alternative hypotheses; (iii) determination of the noninferioritylequivalence margin; (iv) selection of efficient statistical methods for the statistical analysis of noninferioritylequivalence vaccine trials, with particular emphasis on adjustment for stratification factors and missing pre-or post-vaccination data; and (v) the calculation of sample size and power.

Safety and immunogenicity of concomitant versus nonconcomitant administration of hepatitis B, tetanus-diphtheria, and measles-mumps-rubella vaccines in healthy eleven- to twelve-year-olds

PURPOSE

To study safety and immunogenicity of concomitant administration of hepatitis B (HB), Tetanus-diphtheria (Td), and Measles-mumps-rubella (MMR) vaccines in healthy 11-12-year-olds.

METHOD

One hundred ninety-seven healthy 11-12-year-olds from the general community were randomized in an unblinded study to concomitant vaccination with Recombivax HB brand of HB vaccine and Td and MMR vaccines or to HB given at a separate time from Td and MMR vaccination. Primary analyses were for induction of protective immunity and safety. Secondary endpoints were mean geometric antibody titers for HB and a boosting effect for Td and MMR. Differences in immunogenicity were analyzed using the one-sided Pearson's Chi-square test.

RESULTS

Concomitant vaccination for HB, Td, and MMR had a significantly increased incidence of headache, red eyes, and rash compared with nonconcomitant vaccination. There was no significant difference in incidence of serious adverse events, rates of protective immunity, or in secondary endpoints.

CONCLUSIONS

Concomitant HB, Td, and MMR vaccination in 11-12-year-olds is as safe and immunogenic as nonconcomitant vaccination.

Archaeosomes as adjuvants for combination vaccines

The present study evaluated the potential of archaesomes, prepared from the total polar lipids extracted from Methanobrevibacter smithii, as adjuvants for combination (multivalent) vaccines. Groups of Balb/c mice were immunized subcutaneously at day 0 and 21 with one of the following vaccines: trivalent vaccine formulated by the simultaneous co-encapsulation of bovine serum albumine (BSA), ovalbumin (OVA) and hen egg lysozyme (HEL) into archaeosomes (CEC vaccine); an univalent archaeosome vaccine (UVE vaccine) containing either BSA, OVA or HEL; or an admixture vaccine (AMC vaccine) consisting of the three UVE vaccines. Serum specific antibody (IgG + M) responses were determined at day 32, 112 and 203, and specific IgG1 and IgG2a responses were determined at day 112. Mice immunized with the CEC of AMC vaccine developed strong and sustained specific antibody responses to all three antigens at a magnitude similar to those seen in control mice immunized with UVE vaccines. Moreover, the serum BSA-, OVA-, and HEL-specific IgG1 and IgG2a levels in the CEC and AMC immunized mice were overall comparable to those of the UVE immunized control mice. Boosting CEC and AMC vaccinated mice with antigens alone at day 203 elicited strong antibody memory responses, comparable to those in the UVE vaccinated groups. These results show that archaeosomes could be used as adjuvants in developing combination vaccines.

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.

Genetic immunization: what's in a name?

The concept and demonstration of genetic immunization (GI) was first introduced in 1992. At the time it appeared to be a revolutionary new approach in vaccinology. Since then, genetic immunization has been applied with much success in a wide variety of model and natural systems. It has also been used in several human clinical trials. Currently there is a general impression that genetic immunization has limitations inhibiting its broad use. The technique is thought to be poor at antibody production and more importantly not to work well in primates and humans (simian barrier). However, recent reports addressing these issues (poor antibody production and the simian barrier) showed improvements of GI to produce protective immune responses in humans. We propose that the apparent limitations of gene vaccines may arise from not using the technologies' potential to manipulate the immune system. This dearth of imaginative use is manifested in the tendency by some to term the technique DNA immunization. The apparent limitations of DNA vaccines may not be limitations for gene vaccines.

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.

Immunogenicity and reactogenicity of a combined hepatitis A and B vaccine in healthy Chilean subjects

OBJECTIVES

A combination vaccine against hepatitis A and B provides the opportunity for simultaneous protection against both diseases with a single vaccine. This clinical study investigated the reactogenicity and immunogenicity of a combined hepatitis A and B vaccine (Twinrix, GlaxoSmithKline Biologicals, Rixensart, Belgium) in healthy Chilean adults between 18 and 40 years of age.

METHODS

In total, 345 healthy, seronegative health care workers were enrolled and randomized to three groups who received one of three lots of Twinrix on a 0-, 1- and 6-month schedules. Blood samples were screened 1 month after each dose for anti-HAV and anti-HBs antibodies. Reactogenicity after each dose was assessed using diary cards.

RESULTS

The nature and incidence of symptoms were similar to those reported for other Twinrix studies. Very few symptoms were scored as severe. Upon completion of the vaccination, all subjects had anti-HAV antibodies with titers $6000 mIU/mL, and all but one were protected against hepatitis B, with titers $4000 mIU/mL.

CONCLUSIONS

We have demonstrated the high immunogenicity and tolerance of the combined hepatitis A and B vaccine. Combined vaccination has the advantage of offering dual protection with a reduction in the number of injections needed, lower associated costs, and a positive impact on compliance.

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.

Combination vaccines: choices or chaos? A practitioner's perspective

Combination vaccines are necessary and important for the continuing success of our immunization program, especially when more vaccines are added to the already crowded immunization schedule. However, the multiplicity of competing vaccine products, with various overlapping antigen menu and subtle immunologic differences, may be confusing to the busy practitioner. The cost-effectiveness of the use of combination vaccines will depend on a number of factors, including fair and competitive pricing, appropriate reimbursement for vaccine administration fees, and critical economic algorithms for vaccine selection and purchase.

Combination vaccines

The biotechnology revolution has stimulated vaccine development, blessing us with new, safe, and effective vaccines, but burdening our vaccination schedule. The incorporation of multiple individual vaccines into combination vaccines can simplify vaccine administration programs and permit the inclusion of new antigens in the vaccine schedule. Although the development, evaluation, and implementation of combination vaccines pose numerous challenges and raise controversies that remain unresolved, there is a reasonable prospect of United States licensure within the next few years of several new combination vaccines for infant use. Approval in the United States of combination vaccines in use elsewhere might be speeded by improved vaccination tracking systems and post marketing efficacy surveillance, which would provide confidence that material reductions in efficacy could be detected following licensure, and thereby ease concerns regarding moderate, but perhaps immaterial, declines in immunogenicity seen with some combinations.

A combination vaccine confers full protection against co-infections with influenza, herpes simplex and respiratory syncytial viruses

Combined/composite vaccines should be useful in reducing the number of vaccinations and provide more flexibility in confronting biological warfare scenarios. We tested the effectiveness of a composite genetic vaccine designed from previously known protective antigens directed against influenza A virus (INF-A), herpes simplex virus type-1 (HSV-1) and respiratory syncytial virus (RSV) in a mouse-based challenge. Immunizing mice with a pool of four plasmids; INF-A haemagglutinin (HA), INF-A nucleoprotein (NP), HSV-1 glycoprotein D (gD) and RSV glycoprotein F, against the three pathogens provided full protection when mice were challenged with each pathogen. Remarkably, mice challenged with all three pathogens at once were also fully protected, even when a bacterial pathogen, Mycoplasma pulmonis, was included in the challenge. If these results are extendable to other combinations of vaccines in other hosts, it would support the development of gene vaccines as multi-component, combination vaccines.

A prospective, randomized, comparative US trial of a combination hepatitis A and B vaccine (Twinrix) with corresponding monovalent vaccines (Havrix and Engerix-B) in adults

In an open, randomized, multicenter, controlled clinical trial in the US, 773 adults were administered either a combination hepatitis vaccine (Twinrix: 720 EL.U inactivated hepatitis A antigen and 20 mcg recombinant hepatitis B surface antigen per milliliter) on a 0, 1, 6 month schedule or corresponding monovalent vaccines concurrently (Havrix, 1440 EL.U/ml of hepatitis A antigen at 0, 6 months and Engerix-B, 20 mcg of hepatitis B surface antigen at 0, 1, 6 months). Non-inferiority testing for the primary endpoint, severe soreness, and equivalence testing for the secondary endpoints, anti-HAV seroconversion and anti-HBs seroprotection, showed that safety and immunogenicity were comparable in the two groups.

Combination vaccines

The past decade has shown a marked increase in the number of vaccines currently licensed and recommended for use in infants and children. Although most agree that it is desirable to combine as many of these vaccines as possible into a single injection, safety and efficacy must not be sacrificed. Clearly, a resurgence in Hib meningitis or measles (for example) would not be an acceptable price for the convenience of a single injection; but it is not clear how large a reduction in immunogenicity can be incurred without paying such a price. This conundrum has slowed the licensure of useful combination vaccines, despite a consensus that parents and practitioners have reached a limit to the number of injections they will deliver to young children. We anticipate US licensure for infant use of (at least) one DTaP-IPV-Hib vaccine and one DTaP-IPV-HB vaccine within the next few years, given the apparent lack of material reduction in immunogenicity of these specific combination products. Licensure in the United States of some of the other combinations now used in Europe is also possible, given supporting national surveillance data or improvements in our understanding of the correlates of immunity. Enhanced vaccination tracking systems and postmarketing efficacy surveillance should provide confidence that material reductions in efficacy could be detected following licensure, and thereby ease the approval of combinations that result in moderate, but perhaps immaterial, declines in immunogenicity.

A two dose schedule for combined hepatitis A and hepatitis B vaccination in children ages one to eleven years

RATIONALE

A combined hepatitis A and B vaccine, Twinrix, containing at least 720 enzyme-linked immunosorbent assay units of hepatitis A antigen and 20 microg of hepatitis B antigen in the adult formulation and half those doses in the pediatric formulation, has been available in many countries since 1997. This vaccine is administered on a three dose schedule: 0, 1 and 6 months. A reduction in the number of doses would add convenience for the vaccinees and reduce administration-associated costs. We investigated the safety and immunogenicity profile of the adult formulation administered at 0 and 6 months in children ages 1 to 11 years.

METHODS

A total of 237 children of both sexes were enrolled. Blood sampling was performed at 0 and 1, 2, 6 and 7 months. Seropositivity for anti-hepatitis A virus was defined as > or = 33 mIU/ml and seroprotection against hepatitis B virus as > or =10 mIU/ml. Data on solicited and unsolicited adverse events were collected on diary cards.

RESULTS

The vaccine was well-tolerated in all subjects. At Month 7 all subjects had seroconverted for anti-hepatitis A virus antibodies with a high geometric mean concentration (11 543 mIU/ml). We observed a continuous increase in anti-hepatitis B surface antibody (anti-HBs) seroconversion rates and seroprotection rates until Month 6. After the second dose (Month 7), all subjects seroconverted for anti-HBs antibodies with a high geometric mean concentration (8056 mIU/ml) and 98.5% of the subjects were considered seroprotected.

CONCLUSION

The two dose adult formulation could be an alternative to prevent hepatitis A and hepatitis B infection in children ages 1 to 11 years.

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

A combined hepatitis A/B vaccine (Twinrix Adult) has been licensed in Germany since 1997. We investigated possible differences in immunogenicity and safety when changing over from vaccinations with monovalent vaccines made by different manufacturers to vaccinations with the combined hepatitis A/B vaccine in an open, randomized, multicenter trial. We therefore compared four different schemes changing over from concomitant vaccinations with monovalent vaccines against hepatitis A and B (Havrix 1440+Engerix-B or Vaqta+Gen H-B-Vax) to combined vaccination against hepatitis A+B with three injections of the combined hepatitis A/B vaccine (0, 1, and 6 month schedule). Local and general symptoms were mostly mild in all five groups. With complete three-dose course using the combined vaccine or an early changeover from monovalent vaccines to the combined vaccine, higher overall anti-HBs seroprotection rates and geometric mean concentrations (GMCs) against hepatitis B could be achieved as early as after 2 months as compared to those groups switching later to the combined vaccine. This study demonstrated for the first time that switching from monovalent hepatitis A and B vaccinations to the combined hepatitis A and B vaccination has no negative influence on the tolerability and improves the immunogenicity.