Prevention of hepatitis A by Havrix: a review

Modeling hepatitis A epidemiological profiles and estimating the pediatric vaccination threshold in the Russian Federation

Background

To combat the hesitancy towards implementing a hepatitis A universal mass vaccination (UMV) strategy and to provide healthcare authorities with a comprehensive analysis of the potential outcomes and benefits of the implementation of such a vaccination program, we projected HAV seroprevalence and incidence rates in the total population of the Russian Federation and estimated the pediatric vaccination threshold required to achieve an incidence level of less than 1 case per 100,000 using a new mathematical model.

Methods

A dynamic age-structured SEIRV (susceptible-exposed-infectious-recovered-vaccinated) compartmental model was developed and calibrated using demographic, seroprevalence, vaccination, and epidemiological data from different regions of the Russian Federation. This model was used to project various epidemiological measures.

Results

The projected national average age at the midpoint of population immunity increases from 40 years old in 2020 to 50 years old in 2036 and is shifted even further to the age of 70 years in some regions of the country. An increase of varying magnitude in the incidence of symptomatic HAV infections is predicted for all study regions and for the Russian Federation as a whole between 2028 and 2032, if the HAV vaccination coverage level remains at the level of 2022. The national average vaccination coverage level required to achieve a symptomatic HAV incidence rate below 1 case per 100,000 by 2032 was calculated to be 69.8% if children aged 1-6 years are vaccinated following the implementation of a UMV program or 34.8% if immunization is expanded to children aged 1-17 years.

Conclusion

The developed model provides insights into a further decline of herd immunity to HAV against the background of ongoing viral transmission. The current favorable situation regarding hepatitis A morbidity is projected to be replaced by an increase in incidence rates if vaccination coverage remains at the current levels. The obtained results support the introduction of a hepatitis A UMV strategy in the Russian Federation.

Describing mRNA Vaccine Technology for a Military Audience

INTRODUCTION

Vaccine technology has improved substantially since the first smallpox vaccine, developed more than 200 years ago. As technology improves, vaccines can be produced more safely and reliably for many different pathogens. A recent breakthrough saw the first full deployment of mRNA vaccines to fight a pandemic. Despite the technological and logistical feat of developing a viable vaccine in an abbreviated time frame, there have been many questions about this new approach to vaccine development. The current review will provide descriptions about different types of vaccines as well as answers to some common questions about mRNA vaccines. The purpose is to provide military medical professionals with the information needed to better convey the importance and function of these new vaccines to service members.

MATERIALS AND METHODS

There were no explicit inclusion or exclusion criteria for articles describing mRNA vaccine technology. References included here were intended to illustrate important principles or empirical evidence in demonstrating the safety, efficacy, and function of mRNA vaccines.

DISCUSSION

The review describes three different types of vaccines: whole-pathogen, subunit, and nucleic acid. Each vaccine type has different implications for the development and production of a vaccine line. For example, whole-pathogen and subunit vaccines often require growing significant amounts of the vaccine sample in laboratory before the material can be incorporated into the vaccine. Nucleic acid vaccines instead provide cells the opportunity to produce key proteins without needing to reproduce the virus and attenuate it in a laboratory setting. This approach has a notable advantage of speed in moving from genome sequencing to vaccine production, but it also creates some potential confusion. The discussion covers three questions with regard to this confusion. First, was the vaccine developed too quickly? Speed here is a byproduct of the new technology and unprecedented government interdepartmental cooperation. No steps were skipped in development or production. Second, does the vaccine modify DNA? No, the mRNA vaccines never enter the cell nucleus and therefore cannot modify DNA. The discussion clarifies how mRNA enters cells and produces the key proteins required to stimulate an immune system response. Third, how long will immunity last? Because mRNA vaccines are new, long-term immunity cannot be projected without significant further study. Still, the discussion does cover issues in determining vaccine efficacy in clinical laboratory trials versus field effectiveness in the real world.

CONCLUSIONS AND FUTURE USES

These mRNA vaccines are the newest and most sophisticated defensive tool military medicine has against emerging biological threats. Evolving dangers, such as synthetic biology and engineered pathogens, further enhance the importance of having defensive countermeasures that can be rapidly deployed in response. Current evidence suggests high safety and effectiveness for a biological countermeasure, decades in the making, and military medical personnel should feel confident using and recommending this technology to ensure force health protection.

Hepatitis A Immunity and Paediatric Liver Transplantation-A Single-Centre Analysis

Following paediatric solid organ liver transplantation, risk of infection is high, both in the short and long term. Even though an infection with hepatitis A virus (HAV) is often asymptomatic and self-limited in children, some case studies describe severe cases leading to death. Vaccinations offer simple, safe and cheap protection. However, data on vaccination rates against hepatitis A in children with liver disease are scarce. Moreover, the vaccine is only approved from the age of one year old. At the same time, up to 30% of children with liver disease are transplanted within the first year of life, so the window of opportunity for vaccination is limited. This retrospective, observational, single-centre study examines the HAV immunity in paediatric liver transplant recipients before and after the first year of transplantation. Vaccination records of 229 of 279 (82.1%) children transplanted between January 2003 and June 2021 were analysed. Of 139 eligible children aged ≥ 1 year old, only 58 (41.7%) were vaccinated at least with one HAV dose prior to transplantation. In addition, seven patients received the vaccine below one year of age. After one or two doses, 38.5% or 90.6% of 65 patients were anti-HAV-IgG positive, respectively. This percentage remained stable up to the first annual check-up. For children vaccinated only once, a shorter interval from vaccination to transplantation is a risk factor for lack of immunity. Thus, HAV immunisation should be started earlier in liver transplant candidates to improve immunity in this high-risk group.

Dynamic Changes in Hepatitis A Immunity in Regions with Different Vaccination Strategies and Different Vaccination Coverage

The data on hepatitis A virus (HAV) seroprevalence are critical for the implementation of a universal mass vaccination (UMV) strategy. The latter has not been implemented in Russia; however, regional child vaccination programs have been adopted in some parts of the country. The aim of this study is to assess changes in HAV immunity within the last decade in regions of Russia with different vaccination strategies and different vaccination coverage rates. In regions where UMV has not been implemented and HAV vaccination coverage rates do not exceed the national average, the 50% seroprevalence threshold has shifted in the Moscow region from people aged under 40 years in 2008 to people aged over 59 years in 2020, and from people aged under 30 years to people aged over 40 years in the Khabarovsk region. In two regions (Yakutia and Sverdlovsk), a two-dose-based UMV scheme has been in place since 2011 and 2003, respectively, and in Tuva single-dose child immunization was launched in 2012. These regional programs have resulted in a significant increase in HAV seroprevalence in children and adolescents. In Yakutia, 50% herd immunity had been achieved by 2020 in age groups under 20 years, compared to 20−30% seroprevalence rates in 2008. In the Sverdlovsk region, HAV immunity has increased to >65% over the decade in children aged over 10 years, adolescents and young adults, whereas it declined in older age groups. However, a three-fold drop in HAV immunity has occurred in children under 10 years of age, reflecting a significant decline in vaccination coverage. In Tuva, HAV immunity rates in children under 10 years old increased two-fold to exceed 50% by 2020. These data suggest that UMV should be implemented on a national level. Measures to control vaccination coverage and catch-up vaccination campaigns are recommended in order to maintain the effectiveness of existing HAV vaccination programs.

Integrating plant molecular farming and materials research for next-generation vaccines

Biologics - medications derived from a biological source - are increasingly used as pharmaceuticals, for example, as vaccines. Biologics are usually produced in bacterial, mammalian or insect cells. Alternatively, plant molecular farming, that is, the manufacture of biologics in plant cells, transgenic plants and algae, offers a cheaper and easily adaptable strategy for the production of biologics, in particular, in low-resource settings. In this Review, we discuss current vaccination challenges, such as cold chain requirements, and highlight how plant molecular farming in combination with advanced materials can be applied to address these challenges. The production of plant viruses and virus-based nanotechnologies in plants enables low-cost and regional fabrication of thermostable vaccines. We also highlight key new vaccine delivery technologies, including microneedle patches and material platforms for intranasal and oral delivery. Finally, we provide an outlook of future possibilities for plant molecular farming of next-generation vaccines and biologics.

Integrating plant molecular farming and materials research for next-generation vaccines

Biologics - medications derived from a biological source - are increasingly used as pharmaceuticals, for example, as vaccines. Biologics are usually produced in bacterial, mammalian or insect cells. Alternatively, plant molecular farming, that is, the manufacture of biologics in plant cells, transgenic plants and algae, offers a cheaper and easily adaptable strategy for the production of biologics, in particular, in low-resource settings. In this Review, we discuss current vaccination challenges, such as cold chain requirements, and highlight how plant molecular farming in combination with advanced materials can be applied to address these challenges. The production of plant viruses and virus-based nanotechnologies in plants enables low-cost and regional fabrication of thermostable vaccines. We also highlight key new vaccine delivery technologies, including microneedle patches and material platforms for intranasal and oral delivery. Finally, we provide an outlook of future possibilities for plant molecular farming of next-generation vaccines and biologics.

Contemporary strategy to control viral hepatitis A in the Russian Federation

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

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

Advanced Nanobiomedical Approaches to Combat Coronavirus Disease of 2019

New infectious diseases are making themselves known as the human population grows, expands into new regions, and becomes more dense, increasing contact with each other and animal populations. Ease of travel has also increased infectious disease transmission and has now culminated into a global pandemic. The emergence of the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in December 2019 has already infected over 83.7 million people and caused over 1.8 million deaths. While there have been vaccine candidates produced and supportive care implemented, the world is impatiently waiting for a commercially approved vaccine and treatment for the coronavirus disease of 2019 (COVID-19). The different vaccine types investigated for the prevention of COVID-19 all have great promise but face safety obstacles that must be first addressed. Some vaccine candidates of key interest are whole inactivated viruses, adeno-associated viruses, virus-like particles, and lipid nanoparticles. This review examines nanobiomedical techniques for combatting COVID-19 in terms of vaccines and therapeutics.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Prevention of Hepatitis A Virus Infection in the United States: Recommendations of the Advisory Committee on Immunization Practices, 2020

HEPATITIS A IS A VACCINE-PREVENTABLE, COMMUNICABLE DISEASE OF THE LIVER CAUSED BY THE HEPATITIS A VIRUS (HAV). THE INFECTION IS TRANSMITTED VIA THE FECAL-ORAL ROUTE, USUALLY FROM DIRECT PERSON-TO-PERSON CONTACT OR CONSUMPTION OF CONTAMINATED FOOD OR WATER. HEPATITIS A IS AN ACUTE, SELF-LIMITED DISEASE THAT DOES NOT RESULT IN CHRONIC INFECTION. HAV ANTIBODIES (IMMUNOGLOBULIN G [IGG] ANTI-HAV) PRODUCED IN RESPONSE TO HAV INFECTION PERSIST FOR LIFE AND PROTECT AGAINST REINFECTION; IGG ANTI-HAV PRODUCED AFTER VACCINATION CONFER LONG-TERM IMMUNITY. THIS REPORT SUPPLANTS AND SUMMARIZES PREVIOUSLY PUBLISHED RECOMMENDATIONS FROM THE ADVISORY COMMITTEE ON IMMUNIZATION PRACTICES (ACIP) REGARDING THE PREVENTION OF HAV INFECTION IN THE UNITED STATES. ACIP RECOMMENDS ROUTINE VACCINATION OF CHILDREN AGED 12-23 MONTHS AND CATCH-UP VACCINATION FOR CHILDREN AND ADOLESCENTS AGED 2-18 YEARS WHO HAVE NOT PREVIOUSLY RECEIVED HEPATITIS A (HEPA) VACCINE AT ANY AGE. ACIP RECOMMENDS HEPA VACCINATION FOR ADULTS AT RISK FOR HAV INFECTION OR SEVERE DISEASE FROM HAV INFECTION AND FOR ADULTS REQUESTING PROTECTION AGAINST HAV WITHOUT ACKNOWLEDGMENT OF A RISK FACTOR. THESE RECOMMENDATIONS ALSO PROVIDE GUIDANCE FOR VACCINATION BEFORE TRAVEL, FOR POSTEXPOSURE PROPHYLAXIS, IN SETTINGS PROVIDING SERVICES TO ADULTS, AND DURING OUTBREAKS.

Persistence of antibodies 20 y after vaccination with a combined hepatitis A and B vaccine

Vaccination is the most effective and well-tolerated method of conferring long-term protection against hepatitis A and B viruses (HAV; HBV). Long-term studies are required to characterize the duration of protection and need for boosters. Following primary immunization of 150 and 157 healthy adults with 3-doses of combined hepatitis A/hepatitis B vaccine (HAB; Twinrix™, GSK Vaccines, Belgium) at 0-1-6 months in 2 separate studies, we measured vaccine-induced antibody persistence against HAV and HBV annually for 20 y (Study A: NCT01000324; Study B: NCT01037114). Subjects with circulating anti-HAV antibodies < 15 mIU/mL or with anti-hepatitis B surface antigen < 10 mIU/mL were offered an additional monovalent hepatitis A and/or B vaccine dose (Havrix™/Engerix™-B, GSK Vaccines, Belgium). Applying the immunogenicity results from these studies, mathematical modeling predicted long-term persistence. After 20 y, 18 and 25 subjects in studies A and B, respectively, comprised the long-term according-to-protocol cohort for immunogenicity; 100% and 96.0% retained anti-HAV antibodies ≥ 15 mIU/mL, respectively; 94.4% and 92.0% had anti-HBs antibodies ≥ 10 mIU/mL, respectively. Between Years 16–20, 4 subjects who received a challenge dose of monovalent hepatitis A vaccine (N = 2) or hepatitis B vaccine (N = 2), all mounted a strong anamnestic response suggestive of immune memory despite low antibody levels. Mathematical modeling predicts that 40 y after vaccination ≥ 97% vaccinees will maintain anti-HAV ≥ 15 mIU/mL and ≥ 50% vaccinees will retain anti-HBs ≥ 10 mIU/mL. Immunogenicity data confirm that primary immunization with 3-doses of HAB induces persisting anti-HAV and anti-HBs specific antibodies in most adults for up to 20 y; mathematical modeling predicts even longer-term protection.

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

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

Comparison of the safety and immunogenicity of live attenuated and inactivated hepatitis A vaccine in healthy Chinese children aged 18 months to 16 years: results from a randomized, parallel controlled, phase IV study

For large-scale immunization of children with hepatitis A (HA) vaccines in China, accurately designed studies comparing the safety and immunogenicity of the live attenuated HA vaccine (HA-L) and inactivated HA vaccine (HA-I) are necessary. A randomized, parallel controlled, phase IV clinical trial was conducted with 6000 healthy children aged 18 months to 16 years. HA-L or HA-I was administered at a ratio of 1: 1 to randomized selected participants. The safety and immunogenicity were evaluated. Both HA-L and HA-I were well tolerated by all participants. The immunogenicity results showed that the seroconversion rates (HA-L versus HA-I: 98.0% versus 100%, respectively, p >0.05), and geometric mean concentrations in participants negative for antibodies against HA virus IgG (anti-HAV IgG) before vaccination did not differ significantly between the two types of vaccines (HA-L versus HA-I first dose: 898.9 versus 886.2 mIU/mL, respectively, p >0.05). After administration of the booster dose of HA-I, the geometric mean concentrations of anti-HAV IgG (HA-I booster dose: 2591.2 mIU/mL) was higher than that after the first dose (p <0.05) and that reported in participants administered HA-L (p <0.05). Additionally, 12 (25%) of the 48 randomized selected participants who received HA-L tested positive for HA antigen in stool samples. Hence, both HA-L and HA-I could provide acceptable immunogenicity in children. The effects of long-term immunogenicity after natural exposure to wild-type HA virus and the possibility of mutational shifts of the live vaccine virus in the field need to be studied in more detail.

A retrospective pooled analysis assessing the effect of age on the immunogenicity of Havrix™ in healthy adults

Over recent decades, the global incidence of hepatitis A virus infection has been reduced by improvements in sanitation infrastructure and through immunization programs. The immunogenicity and field efficacy of the inactivated hepatitis A vaccine (Havrix™, GSK, Belgium) has been demonstrated in clinical trials, population-impact studies as well as in several outbreak settings. However, immunological data in older populations are limited, with only few studies assessing the immune response of this vaccine in adults aged ≥40 years. This retrospective pooled analysis of 4 2-dose primary vaccination studies compared the immunogenicity and safety of the inactivated hepatitis A vaccine in adults aged ≥40 years with subjects aged 20–30 years (control group; N = 80 in each group). Fifteen days after the first vaccine dose, 79.7% (95% CI: 68.8–88.2) and 92.3% (95% CI: 84.0–97.1) of subjects were seropositive in the ≥40 years and control groups, respectively; 97.5% (95% CI: 91.2–99.7) and 97.4% (95% CI: 91.0–99.7), respectively, were seropositive one month after the first dose. All subjects in both groups (95% CIs: 95.4–100 and 95.3–100, respectively) were seropositive one month after the second dose. Safety profiles were similar in both groups. In conclusion, the inactivated hepatitis A vaccine induced similar immune responses in adults aged ≥40 and 20–30 years one month after the first and second dose whereas younger subjects may demonstrate a higher seroconversion rate 15 days after the first dose.

Viral hepatitis vaccination during pregnancy

Viral hepatitis is a serious global public health problem. It is also a common cause of jaundice and gestational complications in pregnant women. Moreover, infected mothers can transmit the virus to their fetus or neonate, which may increase disease burden and decrease quality of life. To date, commercial vaccines have been developed for hepatitis A, B, and E and are available to the general population. The Advisory Committee on Immunization Practices currently accepts emergency vaccination against hepatitis A and B during pregnancy due to benefits that overweight the potential risks. While there are limited data from trials with limited numbers of samples that suggest the efficacy or safety of hepatitis B and E vaccines in pregnant women, additional data are necessary to provide evidence of vaccination during pregnancy.

Long-term antibody persistence after vaccination with a 2-dose Havrix (inactivated hepatitis A vaccine): 20 years of observed data, and long-term model-based predictions

Antibody persistence in two cohorts of adults, who received inactivated hepatitis A (HAV) vaccine (1440El.U; Havrix; GSK Vaccines) according to a 0-6 or 0-12 month schedule in 1992-1993, has been measured annually. After 20 years, >97% of the subjects in both studies were seropositive for anti-HAV antibodies. Geometric mean concentrations in the according-to-protocol cohorts were 312 mIU/ml in 34/36 subjects vaccinated initially at 0-6 months (NCT00289757) and 317 mIU/ml in 85/86 subjects vaccinated at 0-12 months (NCT00291876). Over the whole follow-up period, seven subjects (2+5, respectively) lost circulating anti-HAV antibodies but mounted a strong response after HAV booster administration (1440El.U). Mathematical modelling, which was applied to assess true persistence at Year 20 (accounting for drop-outs and missing data), and to predict longer-term persistence confirmed previous estimates that seropositive anti-HAV levels would persist in ≥95% vaccinees at Year 30 and ≥90% at Year 40. ClinicalTrials.Gov number: NCT00289757/NCT00291876.

Current status in the therapy of liver diseases

Hepatic diseases, like viral hepatitis, autoimmune hepatitis, hereditary hemochromatosis, non-alcoholic fatty liver disease (NAFLD) and Wilson’s disease, play an important role in the development of liver cirrhosis and, hence, hepatocellular carcinoma. In this review, the current treatment options and the molecular mechanisms of action of the drugs are summarized. Unfortunately, the treatment options for most of these hepatic diseases are limited. Since hepatitis B (HBV) and C (HCV) infections are the most common causes of liver cirrhosis and hepatocellular carcinoma, they are the focus of the development of new drugs. The current treatment of choice for HBV/HCV infection is an interferon-based combination therapy with oral antiviral drugs, like nucleos(t)ide analogues, which is associated with improving the therapeutic success and also preventing the development of resistances. Currently, two new protease inhibitors for HCV treatment are expected (deleobuvir, faldaprevir) and together with the promising drug, daclatasvir (NS5A-inhibitor, currently in clinical trials), adequate therapy is to be expected in due course (circumventing the requirement of interferon with its side-effects), while in contrast, efficient HBV therapeutics are still lacking. In this respect, entry inhibitors, like Myrcludex B, the lead substance of the first entry inhibitor for HBV/HDV (hepatitis D) infection, provide immense potential. The pharmacokinetics and the mechanism of action of Myrcludex B are described in detail.

Seroprotection after hepatitis a vaccination in patients with drug-induced immunosuppression

BACKGROUND

Increasing numbers of travelers using immunosuppressive drugs visit hepatitis A endemic countries. Data on protection rates after hepatitis A vaccination in this group are scarce.

METHODS

In this retrospective study, records of subjects with hepatitis A serology taken after vaccination were searched for in travel clinic databases. Relation between immunosuppressive drug use, age, gender, and time between vaccination and serology was evaluated.

RESULTS

Seroprotection rates within 4 weeks after primary vaccination (50%) are lower than after 4 weeks (64%). After the complete series of two vaccinations seroprotection rates reach 95% although success depends on the immunosuppressive drug being used. Subjects under anti-TNF alpha treatment have significantly lower seroprotection rates than subjects using classical immunosuppressive drugs after the second vaccination. There is no influence of age or gender on seroprotection rates.

CONCLUSIONS

Last-minute vaccination in subjects using immunosuppressive medication is not reliable, only 60% of our subjects had a protective antibody level after a single vaccination. When serology was done within 4 weeks after a single vaccination, seroprotection rates were only 50%, after 4 weeks this number rose to 64%. When persons visit a travel clinic in time for a complete vaccination series, satisfactory seroprotection rates can be reached. Seroprotection rate depends on the drug being used, persons using anti-TNF alpha are less protected.

Comparison of immunogenicity between inactivated and live attenuated hepatitis A vaccines: a single-blind, randomized, parallel-group clinical trial among children in Xinjiang Uighur Autonomous Region, China

OBJECTIVES

To compare immunogenicity among an inactivated hepatitis A vaccine (Healive(®)) with one-dose and two-dose regimens, and three kinds of live attenuated vaccines in children.

METHODS

A single-blind, randomized, parallel-group clinical trial was conducted among healthy children aged 1.5-6 y in Xinjiang Uighur Autonomous Region, China. Subjects were randomly assigned to 5 groups. Two groups were administered one-dose or two-dose inactivated vaccine and the remaining groups were immunized with one of three kinds of attenuated vaccines, respectively. Serum samples were collected at 6- and 12-mo follow-ups. Anti-HAV IgG was measured with a microparticle enzyme immunoassay.

RESULTS

No significant differences were observed in seroconversion rates (seroprotection rates) among the five groups at 6 or 12 mo (p>0.05). The geometric mean concentration (GMC) of anti-HAV IgG was significantly higher in the two-dose Healive(®) group than in the one-dose Healive(®) group and the attenuated vaccine groups at 12 mo (932.4 vs. 112.7, 135.8, 203.3, 212.8 mIU/ml, respectively, p<0.05). In the one-dose Healive(®) group, the GMC was significantly lower than that in the attenuated vaccine B and C groups at 6 mo (152.6 vs. 212, 204 mIU/ml, p<0.05) and at 12 mo (112.7 vs. 203.3, 212.8, p<0.05), but was similar to the attenuated vaccine A group at 12 mo (112.7 vs. 135.8 mIU/ml, p>0.05). The GMCs were significantly higher in the 1-2 y of age group than in the 3-6 y of age group for all types of vaccines except the attenuated vaccine C (p<0.05) at 12 mo.

CONCLUSIONS

A higher GMC of anti-HAV IgG was induced in the two-dose Healive(®) than in the one-dose and the attenuated vaccines at 12 mo. The attenuated vaccine B or C produced higher GMCs than the one-dose Healive(®) at 6-12 mo after vaccination.

Review of 10 years of marketing experience with Chinese domestic inactivated hepatitis A vaccine Healive®

In 2002, the first Chinese domestic preservative-free inactivated hepatitis A vaccine, Healive®, was introduced in China. It is highly immunogenic, and provides lasting protection in healthy individuals and generates protective levels of antibodies in other at-risk individuals. Over 10 years since its first licensure, postmarketing surveillance data have confirmed the outstanding safety profile of the vaccine. Comparative clinical trials indicated that Healive® induce equal or similar immunogenicity with other currently available inactivated hepatitis A vaccines and are interchangeable for the course of HAV immunization in Chinese children. The vaccine is effective in curbing outbreaks of hepatitis A due to rapid seroconversion and the long incubation period of the disease. Additional issues surrounding the use of the vaccine are also reviewed.

Antibody persistence and immune memory in healthy adults following vaccination with a two-dose inactivated hepatitis A vaccine: long-term follow-up at 15 years

Long-term persistence of vaccine-induced immune response in adults was assessed annually for 15 years following primary immunization with a two-dose inactivated hepatitis A vaccine. In 1992, 119 and 194 subjects aged 17-40 years and naïve for hepatitis A virus (HAV) were enrolled in two studies to receive 1,440 ELISA units (El.U) of inactivated hepatitis A vaccine (Havrix™, GlaxoSmithKline Biologicals, Belgium) according to a standard 0, 6 or an extended 0, 12 months schedule, respectively. Serum samples were taken 1 month after the second vaccine dose and every consecutive year up to 15 years after primary vaccination for measurement of anti-HAV antibody concentrations (NCT00291876 and NCT00289757). At year 15, 100% (48/48) and 97.3% (108/111) of subjects vaccinated at 0, 6 or 0, 12 months remained seropositive for anti-HAV antibodies, with geometric mean concentrations (GMCs) of 289.2 and 367.4 mIU/ml, respectively. An additional dose of HAV vaccine (1,440 El.U) was administered to the six subjects who had become seronegative for anti-HAV antibodies since year 11. All subjects mounted a humoral immune response to the additional HAV challenge dose, although post-challenge anti-HAV antibody levels remained low in one subject. These studies represent the longest annual follow-up of hepatitis A vaccine in healthy adults. The immune response induced by two doses of this inactivated HAV vaccine was shown to persist for at least 15 years. No difference in long-term antibody persistence was observed between the two primary vaccination schedules, reinforcing the potential for flexibility in the timing of the second primary vaccine dose.

HPV vaccine: an overview of immune response, clinical protection, and new approaches for the future

Although long-term protection is a key-point in evaluating HPV-vaccine over time, there is currently inadequate information on the duration of HPV vaccine-induced immunity and on the mechanisms related to the activation of immune-memory. Longer-term surveillance in a vaccinated population is needed to identify waning immunity, evaluating any requirements for booster immunizations to assess vaccine efficacy against HPV-diseases. Current prophylactic vaccines have the primary end-points to protect against HPV-16 and 18, the genotypes more associated to cervical cancer worldwide. Nevertheless, data from many countries demonstrate the presence, at significant levels, of HPVs that are not included in the currently available vaccine preparations, indicating that these vaccines could be less effective in a particular area of the world. The development of vaccines covering a larger number of HPVs presents the most complex challenge for the future. Therefore, long term immunization and cross-protection of HPV vaccines will be discussed in light of new approaches for the future.

Hepatitis A: disease burden and current childhood vaccination strategies in the United States

Hepatitis A can be a serious disease and represents a substantial health and economic burden. In recent years, a decline in the number of cases of hepatitis A has been observed, which has been attributed in part to the implementation of vaccination policies in states with high disease incidence. In May 2006, the Advisory Committee on Immunization Practices published updated recommendations to include routine hepatitis A vaccination for all children beginning at 12 to 23 months of age. In this review, information on hepatitis A disease burden is presented with a discussion on the new recommendations and implementation of hepatitis A vaccination.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Efficacy of a prophylactic adjuvanted bivalent L1 virus-like-particle vaccine against infection with human papillomavirus types 16 and 18 in young women: an interim analysis of a phase III double-blind, randomised controlled trial

BACKGROUND

The aim of this interim analysis of a large, international phase III study was to assess the efficacy of an AS04 adjuvanted L1 virus-like-particle prophylactic candidate vaccine against infection with human papillomavirus (HPV) types 16 and 18 in young women.

METHODS

18,644 women aged 15-25 years were randomly assigned to receive either HPV16/18 vaccine (n=9319) or hepatitis A vaccine (n=9325) at 0, 1, and 6 months. Of these women, 88 were excluded because of high-grade cytology and 31 for missing cytology results. Thus, 9258 women received the HPV16/18 vaccine and 9267 received the control vaccine in the total vaccinated cohort for efficacy, which included women who had prevalent oncogenic HPV infections, often with several HPV types, as well as low-grade cytological abnormalities at study entry and who received at least one vaccine dose. We assessed cervical cytology and subsequent biopsy for 14 oncogenic HPV types by PCR. The primary endpoint--vaccine efficacy against cervical intraepithelial neoplasia (CIN) 2+ associated with HPV16 or HPV18--was assessed in women who were seronegative and DNA negative for the corresponding vaccine type at baseline (month 0) and allowed inclusion of lesions with several oncogenic HPV types. This interim event-defined analysis was triggered when at least 23 cases of CIN2+ with HPV16 or HPV18 DNA in the lesion were detected in the total vaccinated cohort for efficacy. Analyses were done on a modified intention-to-treat basis. This trial is registered with the US National Institutes of Health clinical trial registry, number NCT00122681.

FINDINGS

Mean length of follow-up for women in the primary analysis for efficacy at the time of the interim analysis was 14.8 (SD 4.9) months. Two cases of CIN2+ associated with HPV16 or HPV18 DNA were seen in the HPV16/18 vaccine group; 21 were recorded in the control group. Of the 23 cases, 14 (two in the HPV16/18 vaccine group, 12 in the control group) contained several oncogenic HPV types. Vaccine efficacy against CIN2+ containing HPV16/18 DNA was 90.4% (97.9% CI 53.4-99.3; p<0.0001). No clinically meaningful differences were noted in safety outcomes between the study groups.

INTERPRETATION

The adjuvanted HPV16/18 vaccine showed prophylactic efficacy against CIN2+ associated with HPV16 or HPV18 and thus could be used for cervical cancer prevention.

Interchangeability of a hepatitis A vaccine second dose: Avaxim 80 following a first dose of Vaqta 25 or Havrix 720 in children in Turkey

INTRODUCTION

This randomised, observer-blind clinical trial conducted in Turkey evaluated the immunogenicity, safety and interchangeability of three paediatric inactivated hepatitis A vaccines in 424 seronegative children between 1 and 15 years of age.

METHODS

Potential subjects were screened for anti-hepatitis A virus (HAV) antibodies prior to receiving a first dose of Avaxim 80, Havrix 720 or Vaqta 25, followed by a second dose of either the same vaccine or Avaxim 6 months later. Anti-HAV antibody concentrations were measured 2 weeks after the first injection, at 24 weeks (before the second dose) and at 28 weeks for the evaluation of the immune response.

RESULTS

Nearly 80% of the children between 1 and 5 years of age and half of those between the ages of 6 and 10 in the population from which the subjects were recruited were seronegative for HAV antibodies. Two weeks after the first dose, 98.2% of all subjects had anti-HAV antibody concentrations equal to or higher than 20 mIU/mL, believed to be seroprotective, and all subjects were seroprotected before and after the second dose. Anti-HAV geometric mean concentrations (GMCs) 2 weeks after the first dose and before the second were similar in children who received Avaxim and Vaqta (P = 0.2), but both were higher than Havrix (P < 0.01). There were no significant differences in the anti-HAV GMCs between the study groups that received two doses of the same vaccine compared with two doses of different vaccines. There were no significant differences in the frequency of any local or systemic adverse events among the study groups following either of the two doses.

CONCLUSION

All three vaccines are safe and highly immunogenic in healthy children aged 1 to 15 years. Avaxim 80 may also be given as the second dose when Havrix 720 or Vaqta 25 are given as the first dose. The pattern of seroprevalence seen here is similar to that reported in a number of recent evaluations in Turkey, and are supportive of the routine hepatitis A vaccination of young children.

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

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

Long-term immunogenicity after single and booster dose of a live attenuated hepatitis A vaccine: Results from 8-year follow-up

Live, attenuated hepatitis A vaccines are used widely in China but there is uncertainty regarding the persistence of vaccine-induced anti-HAV antibodies after single dose and booster dose administrated at month 12. A large scale clinical trial to evaluate the live, attenuated hepatitis A vaccine was conducted in Hebei province between 1996 and 1999. Five years after the trials, children in single dose and booster dose groups were bled and followed. Seventy two percent (61/85) of children who received a single trial dose had detectable anti-HAV antibodies for 96 months (GMC at 96 months: 89.0 mIU/mL). In the booster group 98% (48/49) children remained anti-HAV positive with GMC of 262.8 mIU/mL at month 96. The reinjection with live attenuated HAV vaccine can elicit a booster effect. Results from single dose group seems not to support the need for booster doses of live attenuated hepatitis A vaccine in immunocompetent individuals regarding the persisting anti-HAV and anamnestic response of a single dose vaccine. Continued monitoring of anti-HAV antibodies is needed for a rational hepatitis A immunization strategy in China.

Long-term protective effect of post-exposure Havrix administration during viral hepatitis Type A outbreaks

Administration of human normal immunoglobulin (HNIG) post-exposure has been routinely used in Slovakia for outbreak control of hepatitis A, but requires deep intramuscular injection, provides only short-lived protection and is a human blood product. The protective effect of post-exposure administration of an inactivated hepatitis A vaccine was evaluated during 10 outbreaks in Slovakia. Direct contacts of confirmed hepatitis A cases received either: a single dose of hepatitis A vaccine (n = 2171) or immunoglobulin (HNIG, n = 3837). In the HNIG group the number of hepatitis A confirmed cases dropped within the first 7 weeks, however the decrease was not as rapid or as marked as that observed in the vaccinated group where the number of hepatitis A cases dropped within the first 4 weeks after vaccination. Among contacts, 67 cases of hepatitis A were detected during the maximum incubation period of 45 days: 16 cases (0.7%) in the vaccine group and 51 cases (1.3%) in the HNIG group (p < 0.05). After two and three years respectively, 50 and 39 volunteers who had previously received one dose of hepatitis A vaccine received a booster dose and anti-HAV antibodies were measured. Differences in anti-HAV antibody GMCs before and after the booster were statistically significant. The longer time interval (3 years instead of 2) between primary vaccination and booster administration did not seem to impact the magnitude of the booster response. The results of this study show that active post-exposure immunisation with only one dose of inactivated vaccine confers high and long-term protection and effectively controls viral hepatitis A outbreaks.

Vaccination against hepatitis A and B: developments, deployment and delusions

PURPOSE OF REVIEW

Current issues in immunization against hepatitis A and B are discussed, including the need to abandon risk-based approaches in favour of universal vaccination, the use of combined hepatitis A and B vaccines and multivalent vaccines, the development of third-generation triple antigen hepatitis B vaccines and polyvalent vaccines.

RECENT FINDINGS

The emergence of hepatitis B surface antigen mutants remains a concern in diagnostic work and immunoprophylaxis and horizontal transmission of the G145R variant stresses the need for surveillance programmes. The more recent and unfounded concerns about the safety of hepatitis B vaccines are noted. Innovative approaches to vaccine production including DNA vaccines and the expression of hepatitis B antigen components in plants (edible vaccines) are reviewed.

SUMMARY

This review describes further evidence to support the introduction of universal immunization against hepatitis B in those countries where this has yet to be implemented. Immunization programmes will continue to evolve to include the administration of polyvalent vaccines in order to best protect populations against infectious diseases.