Long-term protective effects of hepatitis A vaccines. A systematic review

The durability of vaccine-induced protection: an overview

INTRODUCTION

Current vaccines vary widely in both their efficacy against infection and disease, and the durability of the efficacy. Some vaccines provide practically lifelong protection with a single dose, while others provide only limited protection following annual boosters. What variables make vaccine-induced immune responses last? Can breakthroughs in these factors and technologies help us produce vaccines with better protection and fewer doses? The durability of vaccine-induced protection is now a hot area in vaccinology research, especially after COVID-19 vaccines lost their luster. It has fueled discussion on the eventual utility of existing vaccines to society and bolstered the anti-vaxxer camp. To sustain public trust in vaccines, lasting vaccines must be developed.

AREAS COVERED

This review summarizes licensed vaccines' protection. It analyses immunological principles and vaccine and vaccinee parameters that determine longevity of antibodies. The review concludes with challenges and the way forward to improve vaccine durability.

EXPERT OPINION

Despite enormous advances, we still lack essential markers and reliable correlates of lasting protection. Most research has focused on humoral immune responses, but we must also focus on innate, mucosal, and cellular responses - their assessment, correlates, determinants, and novel adjuvants. Suitable vaccine designs and platforms for durable immunity must be found.

High prevalence of hepatitis A and B nonimmunity in pediatric liver transplant recipients

BACKGROUND

Pediatric liver transplant recipients are at increased risk of post-transplant infections. The purpose of this study was to quantify hepatitis A and B non-immunity based on antibody titers in liver transplant recipients.

METHODS

We conducted a retrospective chart review of 107 pediatric liver transplant recipients at a single medical center from 2000 to 2017. We compared hepatitis immune patients to non-immune patients and studied response to vaccination in patients immunized post-transplantation.

RESULTS

Eighty-one percent of patients had pre-transplant immunity to hepatitis A whereas 68% had pre-transplant immunity to hepatitis B. Post-transplant hepatitis B immunity decreased to 33% whereas post-transplant hepatitis A immunity remained high at 82%. Older age and time since transplantation were significantly associated with hepatitis B non-immunity. Most patients responded to doses post-transplantation with 78% seroconversion following hepatitis A re-immunization and 83% seroconversion following hepatitis B re-immunization.

CONCLUSIONS

Pediatric liver transplant recipients are at risk of hepatitis A and B non-immunity, particularly with respect to hepatitis B. Boosters post-transplant may improve immunity to hepatitis viruses.

Hepatitis a Vaccine as Opportunity of Primary Prevention for Food Handlers: A Narrative Review

The hepatitis A virus (HAV) is still a leading cause of viral hepatitis worldwide. After a long incubation period, the clinical manifestations range from asymptomatic infection to acute liver failure. The severity of the disease increases with age and pre-existing liver disease. The transmission is mainly via person-to-person contact or ingestion of contaminated food or water. Food contamination can occur at any step of the food chain, especially when infected people handle not-heated or otherwise-treated food. HAV is endemic in low-income countries because of poor sanitary and sociodemographic conditions. The populations of developed countries are highly susceptible, and large outbreaks occur when HAV is introduced from endemic countries due to globalization, travel, and movement of foodstuffs. HAV prevention includes hygiene practices, immunoglobulins, and vaccination. Safe and effective inactivated and live attenuated vaccines are available and provide long-term protection. The vaccine targets are children and subjects at increased risk of HAV exposure or serious clinical outcomes. This review discusses the critical role of food handlers in the spread of HAV and the opportunity for food industry employers to consider food handler immunization a tool to manage both food safety in compliance with HACCP principles and food operators' biologic risk.

[Cost-effectiveness of universal childhood vaccination against hepatitis A in Spain: a dynamic approach]

OBJECTIVE

To evaluate the cost-effectiveness of infant universal vaccination against hepatitis A in Spain.

METHOD

Using a dynamic model and decision tree model, a cost-effectiveness analysis was performed to compare three vaccination strategies against hepatitis A: non-vaccination strategy versus universal childhood vaccination of hepatitis A with one or two doses. The perspective of the study was that of the National Health System (NHS) and a lifetime horizon was considered. Both costs and effects were discounted at 3% per year. Health outcomes were measured in terms of quality adjusted life years (QALY) and the cost-effectiveness measure used was the incremental cost-effectiveness ratio (ICER). In addition, deterministic sensitivity analysis by scenarios was performed.

RESULTS

In the particular case of Spain, with low endemicity for hepatitis A, the difference in health outcomes between vaccination strategies (with 1 or 2 doses) and non-vaccination are practically non-existent, terms of QALY. In addition, the ICER obtained is high, exceeding the limits of willingness to pay from Spain (€22,000-25,000/QALY). The deterministic sensitivity analysis showed that the results are sensitive to the variations of the key parameters, although in no case the vaccination strategies are cost-effective.

CONCLUSIONS

Universal infant vaccination strategy against hepatitis A would not be a cost-effective option from the NHS perspective in Spain.

Criteria for judging the immune markers of COVID-19 disease vaccines

As severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) sweeping the world, effective and affordable vaccines are in urgent need. A reliable system for the assessment of SARS‐CoV‐2 vaccines would boost the development of vaccines and reduce the research cost. We constructed a logistic regression model and analyzed the relationship between antibody (Ab) level and efficacy of different vaccine types. The relationship between assessment dates and Ab levels was depicted by plotting the mean of Ab levels evolved over time and a fitted cubic polynomial model. Anti‐spike immunoglobulin G (IgG) could best estimate the vaccine efficacy (VE) (adjusted R² = 0.731) and neutralizing Ab to live SARS‐CoV‐2 also explained a fine relationship (adjusted R² = 0.577). Neutralizing Abs to live SARS‐CoV‐2 in inactivated virus vaccines reached a peak during days 40–60, and their receptor‐binding domain (RBD)‐IgG peaked during days 40–50. For messenger RNA (mRNA) and viral vector vaccines, their neutralizing Ab to live SARS‐CoV‐2 peaked later than day 40, and for RBD‐IgG during days 30–50. For mRNA and viral vector vaccines, their peak time of Abs was later than that in inactivated virus vaccines. RBD‐IgG peaked earlier than Ab to live SARS‐CoV‐2. Anti‐spike IgG and Ab to live SARS‐CoV‐2 may be good immune markers for VE assessment.

Hepatitis A Seroprevalence in Mogadishu, Somalia

BACKGROUND

The hepatitis A virus (HAV) is the most frequent global causes of vaccine-preventable viral hepatitis. Since Somalia is regarded as highly endemic for hepatitis A, the hepatitis A vaccine was not included in the World Health Organization's expanded immunization program. The purpose of this study was to determine the prevalence of hepatitis A infection in the Somalia capital, Mogadishu.

METHODS

The serological results of 1153 individuals presenting to the Mogadishu Training and Research Hospital between January 2019 and January 2021 were examined retrospectively to evaluate the presence of anti-HAV IgG and IgM. The seroprevalence of anti-HAV IgG and IgM was analyzed on the basis of age and sex. The seroprevalence of anti-HAV IgG was also compared among the 11-year age group.

FINDINGS

The seroprevalence of anti-HAV IgG and IgM did not vary significantly between the sexes. Overall, the seroprevalence of anti-HAV IgG was 67.6%. The percentage of seropositivity for anti-HAV IgG was highest in adults aged ≥41 years (88.9%) and lowest in children aged 1-2 years (29.4%). Estimated age at midpoint of population immunity was 5 years which is compatible high endemicity. In addition, a significant rate of hepatitis A infection was also observed in the adolescent age group.

CONCLUSIONS

This study confirms the high HAV endemicity in Mogadishu. These data will be useful towards planning preventive and control measures by improving the sanitation programs in Mogadishu. Furthermore, prospective studies are needed to confirm these findings and evaluate urban-rural heterogeneity.

A single blind randomized phase 3 study to evaluate safety and immunogenicity of inactivated hepatitis A vaccine (HAPIBEVTM) in 1-15 years-old healthy hepatitis A vaccine-naïve children

The Biological E inactivated hepatitis A (HAPIBEV™) vaccine was developed by importing the Healive® vaccine bulk from China and fill-finish it in India. Healive® vaccine is approved in China for both children and adults. This study assessed the safety and immunogenicity of HAPIBEV™ vaccine as compared to the Havrix 720® vaccine of GlaxoSmithKline (GSK) pharmaceuticals when administered intramuscularly (IM) 6 months apart in 1-15 years old hepatitis A virus (HAV) vaccine naive children in India. This Phase 3, single blind, parallel, randomized, active-controlled, two-arm study was conducted at 8 centers in India in healthy HAV vaccine-naive children. Subjects were stratified into 2 age subsets (1-7 and 8-15 years) and randomly assigned to either BE-HAPIBEV™ or GSK's Havrix® vaccine and administered 2 IM injections 6 months apart. The immunogenicity evaluations included: (1) proportion of subjects who achieved the following at Day 210 from baseline: (a) seroconversion (≥20 mIU/mL) with anti-HAV immunoglobulin G (IgG) antibodies, (b) ≥4-fold increase in anti-HAV IgG antibodies, and (c) ≥2-fold increase in anti-HAV IgG antibodies concentration who were already seroconverted at baseline and (2) geometric mean concentrations (GMC) of anti-HAV IgG antibodies at baseline and Day 210. Safety was evaluated throughout the study. A total of 467 (89.8%) subjects completed the study. The non-inferiority criterion was met by HAPIBEV™ vaccine as seroconversion rates in both vaccine groups were 100%. Overall, other immunogenicity evaluations were either similar in both vaccine groups or higher in the HAPIBEV™ group compared with the Havrix® group. The safety profile was also comparable between HAPIBEV™ and Havrix® groups. The most common adverse event (AE) was injection site pain, and the majority of AEs were mild in severity. The HAPIBEV™ vaccine demonstrated an immunological and safety profile on par with Havrix® in 1-15 years old healthy HAV vaccine-naive Indian children. This study is registered with clinical trial registry of India bearing no: CTRI/2019/04/018384 on 02 Apr 2019.

Hepatitis A vaccine immunogenicity 25 years after vaccination in Alaska

The hepatitis A vaccine is recommended for all children greater than or equal to 1 year of age, however, the duration of vaccine protection is unknown and protection through adulthood is crucial to prevent symptomatic hepatitis later in life. We report on 25 years of follow-up of a cohort of Alaska Native individuals who were vaccinated in early childhood. We assessed the duration of vaccine protection by calculating the geometric mean concentration and proportion of participants with protective levels of IgG antibody to hepatitis A virus (anti-HAV) (≥20 mIU/mL) every 2 to 3 years. We estimated the amount of time until the anti-HAV dropped below protective levels using survival analyses. At 25 years, 43 of the original 144 participants were available, mean anti-HAV levels were 91.5 mIU/mL, and 35 (81.4%) had protective levels of anti-HAV. Using data from all persons and all time points, a survival analysis estimated 78.7% of participants had protective levels of anti-HAV at 25 years. The high level of protective antibodies in this cohort indicate that supplemental doses of hepatitis A vaccine are not needed 25 years after completion of the vaccine series.

Hepatitis A vaccination and its immunological and epidemiological long-term effects - a review of the evidence

Hepatitis A virus (HAV) infections continue to represent a significant disease burden causing approximately 200 million infections, 30 million symptomatic illnesses and 30,000 deaths each year. Effective and safe hepatitis A vaccines have been available since the early 1990s. Initially developed for individual prophylaxis, HAV vaccines are now increasingly used to control hepatitis A in endemic areas. The human enteral HAV is eradicable in principle, however, HAV eradication is currently not being pursued. Inactivated HAV vaccines are safe and, after two doses, elicit seroprotection in healthy children, adolescents, and young adults for an estimated 30-40 years, if not lifelong, with no need for a later second booster. The long-term effects of the single-dose live-attenuated HAV vaccines are less well documented but available data suggest they are safe and provide long-lasting immunity and protection. A universal mass vaccination strategy (UMV) based on two doses of inactivated vaccine is commonly implemented in endemic countries and eliminates clinical hepatitis A disease in toddlers within a few years. Consequently, older age groups also benefit due to the herd protection effects. Single-dose UMV programs have shown promising outcomes but need to be monitored for many more years in order to document an effective immune memory persistence. In non-endemic countries, prevention efforts need to focus on 'new' risk groups, such as men having sex with men, prisoners, the homeless, and families visiting friends and relatives in endemic countries. This narrative review presents the current evidence regarding the immunological and epidemiological long-term effects of the hepatitis A vaccination and finally discusses emerging issues and areas for research.

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.

Epidemiology of hepatitis A in Greece in the last decade: management of reported cases and outbreaks and lessons learned

Hepatitis A is a mandatory notifiable disease in Greece. Here, we present the epidemiological data for 2009-2018 and the results of outbreak investigations performed, and discuss future public health priorities.Overall, 1193 cases were reported; 320 migrants/refugees, 240 Roma, 112 travellers and 521 from the general population. The median age of the affected general population (37 years) had an increasing trend (from 30.8 years in 2009 to 40.5 in 2018, P < 0.001) and was significantly higher than that among Roma and migrants (7 and 8 years, respectively, P < 0.001). Twenty-two cases (2.2%) were unvaccinated patients with a chronic liver disease. Fifty clusters with 2-12 cases each were recorded; 44 were attributed to person-to-person transmission and six to food consumption. Three outbreaks accounting for 32.3% of the total number of recorded cases were identified; in 2013 among Roma (112 cases), in 2016 among refugees (188 cases) and in 2017 among men having sex with men (96 cases; 33 of them (34.4%) HIV-positive). The epidemiological data depict that improving living conditions and vaccination coverage of deprived populations, and informing adults on the disease focusing at faecal-oral transmission during sexual intercourse and travel should be the future public health priorities.

Characteristics of acute hepatitis A virus infection before and after 2001: A hospital-based study in Tokyo, Japan

BACKGROUND AND AIM

The incidence of acute hepatitis A [AH (A)] is decreasing because of improvements in hygiene; however, cases of sporadic severe hepatitis are still being reported. We assessed the epidemiology of AH (A) in Japan.

METHODS

This was a hospital-based retrospective study, in which 126 AH (A) patients (96 men [76%], median age 39 [range, 19-66] years) were enrolled. Patients diagnosed with AH (A) before 2001 (n = 79) and after 2001 (n = 47) were compared.

RESULTS

The incidence of AH (A) showed peaks in 1990, 1999, and 2018. After 2001, one patient had hepatitis B virus, four had human immunodeficiency virus, and three had syphilis coinfections. Before and after 2001, HAV was transmitted, respectively, by raw oysters (28% and 26%), overseas travel (19% and 28%), and sexual contact (0% and 19%) (P < 0.01). The frequencies of symptoms were appetite loss (51% and 32%), fever (63% and 81%), and diarrhea (3% and 13%) (all P < 0.05), respectively. On admission, the median levels of alanine aminotransferase (1455 and 3069 U/L) and γ-glutamyl transpeptidase (221 and 345 U/L) were significantly higher (P < 0.01), and the prothrombin time (77.5% and 65.9%) and platelet count (22.7 and 16.4 × 10/μL) were significantly lower after 2001 (P < 0.05). A time to normalization of the bilirubin level ≥ 30 days was associated with older age and a diagnosis of AH (A) after 2001.

CONCLUSIONS

Outbreaks and severe AH (A) cases due to sexual transmission have been reported recently. It is necessary to examine their sexual behavior and other sexual infection.

A systematic review of the epidemiology of hepatitis A in Africa

BACKGROUND

Hepatitis A, caused by the hepatitis A virus (HAV), is a vaccine preventable disease. In Low and Middle-Income Countries (LMICs), poor hygiene and sanitation conditions are the main risk factors contributing to HAV infection. There have been, however, notable improvements in hygiene and sanitation conditions in many LMICs. As a result, there are studies showing a possible transition of some LMICs from high to intermediate HAV endemicity. The World Health Organization (WHO) recommends that countries should routinely collect, analyse and review local factors (including disease burden) to guide the development of hepatitis A vaccination programs. Up-to-date information on hepatitis A burden is, therefore, critical in aiding the development of country-specific recommendations on hepatitis A vaccination.

METHODS

We conducted a systematic review to present an up-to-date, comprehensive synthesis of hepatitis A epidemiological data in Africa.

RESULTS

The main results of this review include: 1) the reported HAV seroprevalence data suggests that Africa, as a whole, should not be considered as a high HAV endemic region; 2) the IgM anti-HAV seroprevalence data showed similar risk of acute hepatitis A infection among all age-groups; 3) South Africa could be experiencing a possible transition from high to intermediate HAV endemicity. The results of this review should be interpreted with caution as the reported data represents research work with significant sociocultural, economic and environmental diversity from 13 out of 54 African countries.

CONCLUSIONS

Our findings show that priority should be given to collecting HAV seroprevalence data and re-assessing the current hepatitis A control strategies in Africa to prevent future disease outbreaks.

Anti-HAV evaluation and molecular docking of newly synthesized 3-benzyl(phenethyl)benzo[g]quinazolines

Synthesized 3-benzyl(phenethyl)benzo[g]quinazolines (1-17) were evaluated in vitro to determine their effects against the anti-hepatitis A virus (HAV) using a cytopathic effect inhibition assay. Of the synthesized compounds, 16 and 17 showed considerably high anti-HAV activity, as indicated by their EC₅₀ values of 27.59 and 18 μM, respectively, when compared to that of amantadine (37.3 μM), the standard therapeutic agent. In addition, they exhibited low cytotoxicity as indicated by their CC₅₀ values, 290.63 and 569.45 μM, respectively. Compounds 1, 2, and 5 exhibited remarkable activity compared to the active compounds (16, 17) and amantadine. The selectivity index (SI) values were calculated and applied as a parameter for classifying the activity of the targets. In addition, molecular docking was performed to rationalize the SAR of the target compounds and analyze the binding modes between the docked-selected compounds and amino acid residues in the active site of the HAV-3C proteinase enzyme.

Differential transcriptome and development of human peripheral plasma cell subsets

Human antibody-secreting cells (ASCs) triggered by immunization are globally recognized as CD19loCD38hiCD27hi. Yet, different vaccines give rise to antibody responses of different longevity, suggesting ASC populations are heterogeneous. We define circulating-ASC heterogeneity in vaccine responses using multicolor flow cytometry, morphology, VH repertoire, and RNA transcriptome analysis. We also tested differential survival using a human cell-free system that mimics the bone marrow (BM) microniche. In peripheral blood, we identified 3 CD19+ and 2 CD19- ASC subsets. All subsets contributed to the vaccine-specific responses and were characterized by in vivo proliferation and activation. The VH repertoire demonstrated strong oligoclonality with extensive interconnectivity among the 5 subsets and switched memory B cells. Transcriptome analysis showed separation of CD19+ and CD19- subsets that included pathways such as cell cycle, hypoxia, TNF-α, and unfolded protein response. They also demonstrated similar long-term in vitro survival after 48 days. In summary, vaccine-induced ASCs with different surface markers (CD19 and CD138) are derived from shared proliferative precursors yet express distinctive transcriptomes. Equal survival indicates that all ASC compartments are endowed with long-lived potential. Accordingly, in vivo survival of peripheral long-lived plasma cells may be determined in part by their homing and residence in the BM microniche.

Structural basis for neutralization of hepatitis A virus informs a rational design of highly potent inhibitors

Hepatitis A virus (HAV), an enigmatic and ancient pathogen, is a major causative agent of acute viral hepatitis worldwide. Although there are effective vaccines, antivirals against HAV infection are still required, especially during fulminant hepatitis outbreaks. A more in-depth understanding of the antigenic characteristics of HAV and the mechanisms of neutralization could aid in the development of rationally designed antiviral drugs targeting HAV. In this paper, 4 new antibodies—F4, F6, F7, and F9—are reported that potently neutralize HAV at 50% neutralizing concentration values (neut₅₀) ranging from 0.1 nM to 0.85 nM. High-resolution cryo-electron microscopy (cryo-EM) structures of HAV bound to F4, F6, F7, and F9, together with results of our previous studies on R10 fragment of antigen binding (Fab)-HAV complex, shed light on the locations and nature of the epitopes recognized by the 5 neutralizing monoclonal antibodies (NAbs). All the epitopes locate within the same patch and are highly conserved. The key structure-activity correlates based on the antigenic sites have been established. Based on the structural data of the single conserved antigenic site and key structure-activity correlates, one promising drug candidate named golvatinib was identified by in silico docking studies. Cell-based antiviral assays confirmed that golvatinib is capable of blocking HAV infection effectively with a 50% inhibitory concentration (IC₅₀) of approximately 1 μM. These results suggest that the single conserved antigenic site from complete HAV capsid is a good antiviral target and that golvatinib could function as a lead compound for anti-HAV drug development.

Structures of hepatitis A virus in complex with five neutralizing antibodies reveal a single conserved antigenic site and pinpoint key structure-activity correlates, allowing in silico screening to identify a potent candidate inhibitor drug, golvatinib.

Hepatitis A virus (HAV) is a unique, hepatotropic human picornavirus that infects approximately 1.5 million people annually and continues to cause mortality despite a successful vaccine. There are no licensed therapeutic drugs to date. Better knowledge of HAV antigenic features and neutralizing mechanisms will facilitate the development of HAV-targeting antiviral drugs. In this study, we report 4 potent HAV-specific neutralizing monoclonal antibodies (NAbs), together with our previous reported R10, that efficiently inhibit HAV infection by blocking attachment to the host cell. All 5 epitopes are located within the same patch and are highly conserved across 6 genotypes of human HAV, which suggests a single antigenic site for HAV, highlighting a prime target for structure-based drug design. Analysis of complexes with the 5 NAbs with varying neutralizing activities pinpointed key structure-activity correlates. By using a robust in silico docking method, one promising inhibitor named golvatinib was successfully identified from the DrugBank Database. In vitro assays confirmed its ability to block viral infection and revealed its neutralizing mechanism. Our approach could be useful in the design of effective drugs for picornavirus infections.

Very low prevalence of anti-HAV in Japan: high potential for future outbreak

Since the early 21^st century, almost all developed countries have had a very low hepatitis A virus antibody (anti-HAV) sero-prevalence profile, as sanitation conditions and health care facilities have been optimized to a universal standard. There has not been a report on anti-HAV prevalence among a large scale population in Japan since 2003. Therefore, this study aimed to investigate the current HAV status among the general population in Hiroshima. From each age and sex specific group, a total of 1,200 samples were randomly selected from 7,682 stocked serum samples from residents' and employees' annual health check-ups during 2013-2015. Total anti-HAV was detected using Chemiluminescent Enzyme Immunoassay. The overall anti-HAV sero-prevalence was 16.8%. In both males and females, anti-HAV prevalence among individuals between 20-59 years of age was as low as 0.0-2.0%, whilst that among 70 s was as high as 70.0-71.0%. A large number of residents aged under 60 are now susceptible to HAV infection. The cohort reduction trend of anti-HAV in Japan exposes the high possibility of mass outbreak in the future. HAV vaccine especially to younger generation and high risk population may prevent outbreak in Japan.

Clinical factors associated with hepatitis B screening and vaccination in high-risk adults

BACKGROUND

Hepatitis B virus is a viral infection that can lead to acute and/or chronic liver disease, and hepatocellular carcinoma (HCC). Hepatitis B vaccination is 95% effective in preventing infection and the development of chronic liver disease and HCC due to hepatitis B. In 2011, the Centers for Disease Control updated their guidelines recommending that adults at high-risk for hepatitis B infection be vaccinated against hepatitis B including those with diabetes mellitus (DM). We hypothesize that adults at high-risk for hepatitis B infection are not being adequately screened and/or vaccinated for hepatitis B in a large urban healthcare system.

AIM

To investigate clinical factors associated with Hepatitis B screening and vaccination in patients at high-risk for Hepatitis B infection.

METHODS

We conducted a retrospective review of 999 patients presenting at a large urban healthcare system from 2012-2017 at high-risk for hepatitis B infection. Patients were considered high-risk for hepatitis B infection based on hepatitis B practice recommendations from the Center for Disease Control. Medical history including hepatitis B serology, concomitant medical diagnoses, demographics, insurance status and social history were extracted from electronic health records. Multivariate logistic regression was used to identify clinical risk factors independently associated with hepatitis B screening and vaccination.

RESULTS

Among the 999 patients, 556 (55.7%) patients were screened for hepatitis B. Of those who were screened, only 242 (43.5%) patients were vaccinated against hepatitis B. Multivariate regression analysis revealed end-stage renal disease [odds ratio (OR): 5.122; 2.766-9.483], alcoholic hepatitis (OR: 3.064; 1.020-9.206), and cirrhosis or end-stage liver disease (OR: 1.909; 1.095-3.329); all P < 0.05 were associated with hepatitis B screening, while age (OR: 0.785; 0.680-0.906), insurance status (0.690; 0.558-0.854), history of DM (OR: 0.518; 0.364-0.737), and human immunodeficiency virus (OR: 0.443; 0.273-0.718); all P < 0.05 were instead not associated with hepatitis B screening. Of the adults vaccinated for hepatitis B, multivariate regression analysis revealed age (OR: 0.755; 0.650-0.878) and DM were not associated with hepatitis B vaccination (OR: 0.620; 0.409-0.941) both P < 0.05.

CONCLUSION

Patients at high-risk for hepatitis B are not being adequately screened and/or vaccinated. Improvements in hepatitis B vaccination should be strongly encouraged by all healthcare systems.

Viruses Associated With Foodborne Infections

Foodborne pathogens cause acute and chronic health outcomes of very different durations, severity and mortality, resulting in high costs and burdens to society. The issues of food safety and food poisoning are being increasingly emphasised, particularly in developed countries. Infection/contamination with many agents i.e., bacterial, parasitic and viral entities can result in foodborne illness. This article will focus mainly on viral agents of infection.

A range of different viruses can cause food poisoning/foodborne infection, and infection can result in a myriad of symptoms, ranging from mild, acute disease to chronic, debilitating disease and even death. Due to the inherent differences between bacteria and viruses, namely the fact that viruses do not replicate in food, while bacteria do, viruses are frequently difficult to detect. This is compounded by the fact that many of the viruses associated with enteric disease do not replicate in cell culture. These factors can lead to a lag between reporting, detection and analysis of foodborne viruses versus bacterial agents. Despite these constraints, it is now evident that there are both well-established and emerging viruses implicated in foodborne infections, and the role of molecular detection and characterisation is becoming increasingly important.

Hepatitis A vaccine immune response 22 years after vaccination

In the United States, the incidence of hepatitis A virus (HAV) infection has been reduced through universal childhood vaccination. However, the duration of immunogenicity for the hepatitis A vaccine is not known. We report on the 22 year follow-up time point of a cohort of Alaska children who were randomized to three different vaccine schedules: A) 0, 1, and 2 months; B) 0, 1, and 6 months; and C) 0, 1, and 12 months. Among 46 participant available for follow-up, 40 (87%) maintained protective levels of anti-hepatitis A antibody. These results indicate that a supplemental booster dose is not yet necessary at or before the 22-year time point.

Investigating a community wide outbreak of hepatitis A in Kerala, India

Background:

There was an outbreak of acute hepatitis in Nellikuzhy panchayat of Kothamangalam taluk, Ernakulam district, Kerala, during November and early December 2016. Objective of this study is to describe the epidemiological features of the outbreak and to identify the probable source.

Materials and Methods:

The outbreak was defined in terms of time, place, and person. A hypothesis was generated and tested using a case–control study. Cases were selected by simple random sampling from the line list and controls were age-matched neighborhood individuals without any history of jaundice. Chi-square test, univariate analysis, and multi-variate logistic regression analyses were done to identify the probable risk factors.

Results:

Around 223 hepatitis A cases were identified. Attack rate was found to be highest among the age group of 16-30 years at 1.44% and was eight times higher among males. Epidemic curve suggested a point source outbreak possibly from exposure to food or water from a newly opened hotel in the area. The case–control study confirmed the hypothesis with a statistically significant association between cases and history of exposure to food from the hotel [OR 120; 95% CI 14.6–996.2; P value < 0.001].

Conclusion:

Observations and results of the case–control study revealed that the probable source of the Hepatitis A outbreak at Nellikuzhy panchayat was a hotel. The study findings also add evidences to the changing epidemiological pattern of hepatitis A in Kerala, and warrant the necessity to enforce food safety rules in the State.

A Recombinant HAV Expressing a Neutralization Epitope of HEV Induces Immune Response against HAV and HEV in Mice

Hepatitis A virus (HAV) and hepatitis E virus (HEV) are causative agents of acute viral hepatitis transmitted via the fecal–oral route. Both viruses place a heavy burden on the public health and economy of developing countries. To test the possibility that HAV could be used as an expression vector for the development of a combination vaccine against hepatitis A and E infections, recombinant HAV-HEp148 was created as a vector to express an HEV neutralization epitope (HEp148) located at aa 459–606 of the HEV capsid protein. The recombinant virus expressed the HEp148 protein in a partially dimerized state in HAV-susceptible cells. Immunization with the HAV-HEp148 virus induced a strong HAV- and HEV-specific immune response in mice. Thus, the present study demonstrates a novel approach to the development of a combined hepatitis A and E vaccine.

Type A viral hepatitis: A summary and update on the molecular virology, epidemiology, pathogenesis and prevention

Although epidemic jaundice was well known to physicians of antiquity, it is only in recent years that medical science has begun to unravel the origins of hepatitis A virus (HAV) and the unique pathobiology underlying acute hepatitis A in humans. Improvements in sanitation and the successful development of highly efficacious vaccines have markedly reduced the worldwide prevalence and incidence of this enterically-transmitted infection over the past quarter century, yet the virus persists in vulnerable populations and remains a common cause of food-borne disease outbreaks in economically-advantaged societies. Reductions in the prevalence of HAV have led to increases in the median age at which infection occurs, often resulting in more severe disease in affected persons and paradoxical increases in disease burden in some developing nations. Here, we summarize recent advances in the molecular virology of HAV, an atypical member of the Picornaviridae family, survey what is known of the pathogenesis of hepatitis A in humans and the host-pathogen interactions that typify the infection, and review medical and public health aspects of immunisation and disease prevention.

Persistence of antibody to Hepatitis A virus 20 years after receipt of Hepatitis A vaccine in Alaska

Hepatitis A vaccine is recommended for children ≥1 year old to prevent hepatitis A virus (HAV) infection. However, the duration of vaccine-induced immunity is unknown. We evaluated a cohort of Alaska Native persons 20 years after HAV vaccination. Children aged 3-6 years had been previously randomized to receive three doses of HAV vaccine (360 ELISA units/dose) at: (i) 0,1,2 months; (ii) 0,1,6 months; and (iii) 0,1,12 months. We measured anti-HAV antibody concentrations every 2-3 years; described geometric mean concentrations (GMC) and the proportion with protective antibody (≥20 mIU mL^-1 ) over time; and modelled the change in GMC using fractional polynomial regression. Of the 144 participants, after 20 years 52 (36.1%) were available for the follow-up (17, 18, 17 children in Groups A, B and C, respectively). Overall, 46 (88.5%) of 52 available participants had anti-HAV antibody concentrations ≥20 mIU mL^-1 , and overall GMC was 107 mIU mL^-1 . Although GMC levels were lower in Group A (60; CI 34-104) than in Group B (110; CI 68-177) or Group C (184; CI 98-345) (B vs C: P=.168; A vs B/C: P=.011), there was no difference between groups after adjusting for peak antibody levels post-vaccination (P=.579). Models predicted geometric mean concentrations of 124 mIU mL^-1 after 25 years, and 106 mIU mL^-1 after 30 years. HAV vaccine provides protective antibody levels 20 years after childhood vaccination. Lower antibody levels in Group A may be explained by a lower initial peak response. Our results suggest a booster vaccine dose is unnecessary for at least 25-30 years.

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.

[Immunisation schedule of the Spanish Association of Paediatrics: 2015 recommendations]

The Advisory Committee on Vaccines of the Spanish Association of Paediatrics updates the immunisation schedule every year, taking into account epidemiological data as well as evidence on the safety, effectiveness and efficiency of current vaccines, including levels of recommendation. In our opinion, this is the optimal vaccination calendar for all children resident in Spain. Regarding the vaccines included in the official unified immunization schedule, the Committee emphasizes the administration of the first dose of hepatitis B either at birth or at 2 months of life; the recommendation of the first dose of MMR and varicella vaccine at the age of 12 months, with the second dose at the age of 2-3 years; DTaP or Tdap vaccine at the age of 6 years, followed by another Tdap booster dose at 11-12 years old; Tdap strategies for pregnant women and household contacts of the newborn, and immunization against human papillomavirus in girls aged 11-12 years old with a 2 dose scheme (0, 6 months). The Committee reasserts its recommendation to include vaccination against pneumococcal disease in the routine immunisation schedule, the same as it is being conducted in Western European countries. The recently authorised meningococcal B vaccine, currently blocked in Spain, exhibits the profile of a universal vaccine. The Committe insists on the need of having the vaccine available in communitary pharmacies. It has also proposed the free availability of varicella vaccines. Their efectiveness and safety have been confirmed when they are administred from the second year of life. Vaccination against rotavirus is recommended in all infants. The Committee stresses the need to vaccinate population groups considered at risk against influenza and hepatitis A.

The impact of assumptions regarding vaccine-induced immunity on the public health and cost-effectiveness of hepatitis A vaccination: Is one dose sufficient?

Hepatitis A vaccination stimulates memory cells to produce an anamnestic response. In this study, we used a mathematical model to examine how long-term immune memory might convey additional protection against clinical/icteric infections. Dynamic and decision models were used to estimate the expected number of cases, and the costs and quality-adjusted life-years (QALYs), respectively. Several scenarios were explored by assuming: (1) varying duration of vaccine-induced immune memory, (2) and/or varying levels of vaccine-induced immune memory protection (IMP), (3) and/or varying levels of infectiousness in vaccinated individuals with IMP. The base case analysis assumed a time horizon of 25 y (2012 - 2036), with additional analyses over 50 and 75 y. The analyses were conducted in the Mexican public health system perspective. In the base case that assumed no vaccine-induced IMP, the 2-dose hepatitis A vaccination strategy was cost-effective compared with the 1-dose strategy over the 3 time horizons. However, it was not cost-effective if we assumed additional IMP durations of at least 10 y in the 25-y horizon. In the 50- and 75-y horizons, the 2-dose strategy was always cost-effective, except when 100% reduction in the probability of icteric Infections, 75% reduction in infectiousness, and mean durations of IMP of at least 50 y were assumed. This analysis indicates that routine vaccination of toddlers against hepatitis A virus would be cost-effective in Mexico using a single-dose vaccination strategy. However, the cost-effectiveness of a second dose depends on the assumptions of additional protection by IMP and the time horizon over which the analysis is performed.

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.

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.

Persistence of seropositivity among persons vaccinated for hepatitis A during infancy by maternal antibody status: 15-year follow-up

The effect of passively transferred maternal antibody to hepatitis A virus (anti-HAV) on the duration of seropositivity after hepatitis A vaccination during infancy and early childhood is unclear. We obtained levels of anti-HAV at intervals through age 15-16 years among three groups of Alaskan Native children who initiated a two-dose inactivated hepatitis A vaccination series at ages 6 months (group 1), 12 months (group 2), and 15 months (group 3), each group randomized according to maternal anti-HAV status. Seropositivity (anti-HAV ≥20 mIU/mL) 30 years after the second vaccine dose among the three groups was predicted using a random effects model. One hundred eighty-three children participated in the study; follow-up did not differ significantly by vaccine group or maternal anti-HAV status. Although the frequency of seropositivity among all participants through age 10 years was high (100% among groups 2 and 3 and >90% among group 1), there was a decrease thereafter through age 15-16 years among group 1 children, who initiated vaccination at age 6 months (50%-75%), and among maternal anti-HAV-positive children in groups 2 and 3 (67%-87%), who initiated vaccination at ages 12 months and 15 months, respectively. Nonetheless, the model indicated that anti-HAV seropositivity should persist for ≥30 years after vaccination in 64% of all participants; among those seropositive at age 15-16 years, 84% were predicted to remain so for ≥30 years.

CONCLUSION

Most children vaccinated during early childhood available for sampling maintained seropositivity through age 15-16 years; however, seropositivity was less frequent among those starting vaccination at age 6 months and among maternal antibody-positive participants who started vaccination at age 12 months or 15 months; overall, our findings support current vaccine recommendations and continued follow-up of this cohort.

Immunogenicity and safety of a pediatric dose of a virosomal hepatitis A vaccine in healthy children in India

As India is transitioning from high to intermediate hepatitis A endemicity, the need for hepatitis A vaccination programs increases. This study investigated the immunogenicity and safety of a virosomal hepatitis A vaccine (HAVpur Junior) compared with an aluminum-adsorbed hepatitis A vaccine (Havrix 720 Junior) in Indian children. Healthy children aged 18-47 months, stratified by age, were randomized to either HAVpur Junior or Havrix 720 Junior. The first dose of vaccine was administered on Day 1 and the second (booster) dose 6 months later. Antibodies against hepatitis A virus (HAV) were measured using a microparticle enzyme immunoassay. The primary objective assessed non-inferiority of HAVpur Junior to Havrix 720 Junior in terms of seroprotection rates (≥ 10 mIU/mL anti-HAV antibodies) at 1 month after the first vaccination. Non-inferiority was demonstrated if the lower limit of the 90% confidence interval of the group difference was greater than -10%. Local and systemic adverse events were recorded. The seroprotection rate at 1 month was 95.9% in the HAVpur Junior group and 96.6% in the Havrix 720 Junior group. As the lower limit of the 90% confidence interval of the group difference was greater than -10% (-4.7), non-inferiority of HAVpur Junior to Havrix 720 Junior was established. The overall incidence of adverse events (solicited and unsolicited) after each vaccination was similar in both groups. In conclusion, the aluminum-free virosomal vaccine HAVpur Junior induced a similar immune response to Havrix 720 Junior in healthy Indian children aged 18 to 47 months. Both vaccines were well tolerated. The study shows that the low-dose virosomal HAV vaccine is consistently efficacious and well tolerated in children of all age groups and is suitable for inclusion into Indian childhood vaccination schedules.

Decreasing immunity to hepatitis A virus infection among US adults: Findings from the National Health and Nutrition Examination Survey (NHANES), 1999-2012

BACKGROUND

The clinical course of hepatitis A virus (HAV) infection is more severe with increased age. In the United States, surveillance data reported to CDC since 2011 indicate increases in both the absolute number of cases and the mean age of cases. Total antibody to HAV (anti-HAV) is a marker of immunity.

METHODS

We analyzed National Health and Nutrition Examination Survey (NHANES) data for anti-HAV from respondents aged ≥ 2 years collected from 2007 to 2012 and compared with data collected 10 years earlier (1999-2006). For US-born adults aged ≥ 20 years, we estimated age-adjusted anti-HAV prevalence by demographic and other characteristics, evaluated factors associated with anti-HAV positivity and examined anti-HAV prevalence by decade of birth.

RESULTS

The prevalence of anti-HAV among adults aged ≥ 20 years was 24.2% (95% CI 22.5-25.9) during 2007-2012, a significant decline from 29.5% (95% CI 28.0-31.1) during 1999-2006. Prevalence of anti-HAV was consistently lower in 2007-2012 compared to 1999-2006 by all characteristics examined. In 2007-2012, the lowest age-specific prevalence was among adults aged 30-49 years (16.1-17.6%). Factors significantly associated with anti-HAV positivity among adults were older age, Mexican American ethnicity, living below poverty, less education, and not having insurance. By decade of birth, the prevalence of anti-HAV was slightly lower in 2009-2012 than in 1999-2002, except among persons born from 1980 to 1989.

CONCLUSIONS

NHANES data document very low prevalence of hepatitis A immunity among U.S. adults aged 30-49 years; waning of anti-HAV over time may be minimal. Improving vaccination coverage among susceptible adults should be considered.

Gut microbiota modulate the immune effect against hepatitis B virus infection

The immunological mechanisms by which hepatitis B virus (HBV) initiates and maintains acute or chronic infection, even the formation of cirrhosis and hepatocellular carcinoma, are still undefined. An increasing number of studies have shown that intestinal flora regulate immune homeostasis, and, thus, protect the immunologic function against hepatitis virus infection. In this article, we discuss gut microbiota and its potential immune effects against HBV infection. It may provide a novel insight into the pathogenesis of HBV infection, as well as a potential therapeutic target to HBV-related disease.

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.

Public Health Impact and Cost-Effectiveness of Hepatitis A Vaccination in the United States: A Disease Transmission Dynamic Modeling Approach

OBJECTIVE

To assess the population-level impact and cost-effectiveness of hepatitis A vaccination programs in the United States.

METHODS

We developed an age-structured population model of hepatitis A transmission dynamics to evaluate two policies of administering a two-dose hepatitis A vaccine to children aged 12 to 18 months: 1) universal routine vaccination as recommended by the Advisory Committee on Immunization Practices in 2006 and 2) Advisory Committee on Immunization Practices's previous regional policy of routine vaccination of children living in states with high hepatitis A incidence. Inputs were obtained from the published literature, public sources, and clinical trial data. The model was fitted to hepatitis A seroprevalence (National Health and Nutrition Examination Survey II and III) and reported incidence from the National Notifiable Diseases Surveillance System (1980-1995). We used a societal perspective and projected costs (in 2013 US $), quality-adjusted life-years, incremental cost-effectiveness ratio, and other outcomes over the period 2006 to 2106.

RESULTS

On average, universal routine hepatitis A vaccination prevented 259,776 additional infections, 167,094 outpatient visits, 4781 hospitalizations, and 228 deaths annually. Compared with the regional vaccination policy, universal routine hepatitis A vaccination was cost saving. In scenario analysis, universal vaccination prevented 94,957 infections, 46,179 outpatient visits, 1286 hospitalizations, and 15 deaths annually and had an incremental cost-effectiveness ratio of $21,223/quality-adjusted life-year when herd protection was ignored.

CONCLUSIONS

Our model predicted that universal childhood hepatitis A vaccination led to significant reductions in hepatitis A mortality and morbidity. Consequently, universal vaccination was cost saving compared with a regional vaccination policy. Herd protection effects of hepatitis A vaccination programs had a significant impact on hepatitis A mortality, morbidity, and cost-effectiveness ratios.

Impact of Hepatitis A vaccination with a two-dose schedule in Panama: Results of epidemiological surveillance and time trend analysis

PURPOSE

In April 2007, Panama introduced Hepatitis A universal vaccination using a two-dose schedule (Havrix(®)junior; GSK Vaccines, Belgium). We assessed the impact of this hepatitis A vaccine three years after it was recommended for universal mass vaccination in Panama.

MATERIALS AND METHODS

Hepatitis A vaccination impact was assessed using two different approaches. The first approach used retrospective data (incidence and number of cases for all age groups), collected from the passive surveillance of the Epidemiologic Surveillance System of the Ministry of Health of hepatitis A and unspecified hepatitis before (2000-2006) and after (2008-2010) introduction of hepatitis A vaccine. The second approach was a prospective hospital-based active surveillance for hepatitis cases conducted in subjects (0-14 years) during 2009-2011 at three sentinel hospitals in Panama.

RESULTS

Overall, the annual incidence of hepatitis A and unspecified hepatitis in 2008, 2009 and 2010 were 13.1, 7.9 and 3.7 per 100,000 subjects, lower than the baseline incidence of 51.1 per 100,000 subjects. In comparison to the mean baseline period (2000-2006), there was an 82% mean reduction in the overall hepatitis-related outcomes (hepatitis A and unspecified hepatitis) after vaccine introduction (2008-2010) in all age groups. In the hospital-based surveillance (2009-2011), of the 42 probable viral hepatitis A cases, nine cases were confirmed as acute hepatitis A (8 in 2009, 1 in 2010). Of these confirmed cases, two belonged to the targeted vaccine group (1-4 years) but were not vaccinated.

CONCLUSIONS

Our study suggests that the introduction of two-dose hepatitis A vaccines in Panama has contributed to the reduction in the incidence of overall hepatitis-related outcomes for all age groups, suggesting herd protection. Additional monitoring is required to document a sustained long-term effect.

Long-term antibody persistence in children after vaccination with the pediatric formulation of an aluminum-free virosomal hepatitis A vaccine

BACKGROUND

The pediatric dose of the virosomal hepatitis A vaccine Epaxal, Epaxal Junior, is safe and immunogenic in children from 1 to 17 years of age. The present study investigated the long-term immunogenicity of Epaxal Junior. The standard doses of Epaxal and aluminum-adsorbed hepatitis A vaccine (Havrix Junior) were used as comparators.

METHODS

A total of 271 children who had completed a 0/6-month immunization schedule (priming and booster dose) participated in this follow-up study. Anti-hepatitis A virus (HAV) antibody levels were measured using a microparticle enzyme immunoassay (HAVAB 2.0 Quantitative; Abbott Diagnostics, Wiesbaden, Germany) starting at 18 months following the second dose, and then yearly until 66 months (ie, 5.5 years) after the second dose.

RESULTS

All subjects tested at Month 66 still had protective anti-HAV antibodies (≥10 mIU/mL). Antibody titers were generally lower in subjects 1-7 years old than in subjects 8-17 years old and higher in females 11-17 years old than in males 11-17 years old. In addition, an age-dependent decay was observed, that is, antibody decreased more rapidly in younger than in older children.

CONCLUSIONS

Vaccination of children with two doses of Epaxal Junior confers a real-time protection of at least 5.5 years. This protection is estimated to last approximately 25 years. Younger children showed lower antibody titers and a faster antibody decline than older children. Additional follow-up studies are needed beyond 5.5 years to further assess the long-term immunogenicity of Epaxal Junior.

Considerations on the current universal vaccination policy against hepatitis A in Greece after recent outbreaks

Greece is the only European Union member state that in 2008 included hepatitis A (HAV) vaccine in the routine national childhood immunization program (NCIP). Given that the resources allocated to public health have dramatically decreased since 2008 and that Greece is a low endemicity country for the disease, the benefit from universal vaccination has been questioned. The aim of this paper is to summarize the available epidemiological data of the disease for 1982-2013, and discuss the effects of universal vaccination on disease morbidity. Descriptive analysis, ARIMA modeling and time series intervention analysis were conducted using surveillance data of acute HAV. A decreasing trend of HAV notification rate over the years was identified (p<0.001). However, universal vaccination (~ 80% vaccine coverage of children) had no significant effect on the annual number of reported cases (p = 0.261) and has resulted to a progressive increase of the average age of infection in the general population. The mean age of cases before the inclusion of the vaccine to NCIP (24.1 years, SD = 1.5) was significantly lower than the mean age of cases after 2008 (31.7 years, SD = 2.1) (p<0.001). In the last decade, one third of all reported cases were Roma (a population accounting for 1.5% of the country’s total population) and in 2013 three outbreaks with 16, 9 and 25 Roma cases respectively, were recorded, indicating the decreased effectiveness of the current immunization strategy in this group. Data suggest that universal vaccination may need to be re-considered. Probably a more cost effective approach would be to implement a program that will include: a) vaccination of high risk groups, b) universal vaccination of Roma children and improving conditions at Roma camps, c) education of the population and travel advice, and d) enhancement of the control measures to increase safety of shellfish and other foods.

Long antibody persistence and transgenerational transfer of immunity in a long-lived vertebrate

Although little studied in natural populations, the persistence of immunoglobulins may dramatically affect the dynamics of immunity and the ecology and evolution of host-pathogen interactions involving vertebrate hosts. By means of a multiple-year vaccination design against Newcastle disease virus, we experimentally addressed whether levels of specific antibodies can persist over several years in females of a long-lived procellariiform seabird-Cory's shearwater-and whether maternal antibodies against that antigen could persist over a long period in offspring several years after the mother was exposed. We found that a single vaccination led to high levels of antibodies for several years and that the females transmitted antibodies to their offspring that persisted for several weeks after hatching even 5 years after a single vaccination. The temporal persistence of maternally transferred antibodies in nestlings was highly dependent on the level at hatching. A second vaccination boosted efficiently the level of antibodies in females and thus their transfer to offspring. Overall, these results stress the need to consider the temporal dynamics of immune responses if we are to understand the evolutionary ecology of host-parasite interactions and trade-offs between immunity and other life-history characteristics, in particular in long-lived species. They also have strong implications for conservation when vaccination may be used in natural populations facing disease threats.

Molecular biology and inhibitors of hepatitis A virus

Hepatitis A virus (HAV) is a faeco-orally transmitted picornavirus and is one of the main causes of acute hepatitis worldwide. An overview of the molecular biology of HAV is presented with an emphasis on recent findings. Immune evasion strategies and a possible correlation between HAV and atopy are discussed as well. Despite the availability of efficient vaccines, antiviral drugs targeting HAV are required to treat severe cases of fulminant hepatitis, contain outbreaks, and halt the potential spread of vaccine-escape variants. Additionally, such drugs could be used to shorten the period of illness and decrease associated economical costs. Several known inhibitors of HAV with various mechanisms of action will be discussed. Since none of these molecules is readily useable in the clinic and since the availability of an anti-HAV drug would be of clinical importance, increased efforts should be targeted toward discovery and development of such antivirals.

How advances in immunology provide insight into improving vaccine efficacy

Vaccines represent one of the most compelling examples of how biomedical research has improved society by saving lives and dramatically reducing the burden of infectious disease. Despite the importance of vaccinology, we are still in the early stages of understanding how the best vaccines work and how we can achieve better protective efficacy through improved vaccine design. Most successful vaccines have been developed empirically, but recent advances in immunology are beginning to shed new light on the mechanisms of vaccine-mediated protection and development of long-term immunity. Although natural infection will often elicit lifelong immunity, almost all current vaccines require booster vaccination in order to achieve durable protective humoral immune responses, regardless of whether the vaccine is based on infection with replicating live-attenuated vaccine strains of the specific pathogen or whether they are derived from immunization with inactivated, non-replicating vaccines or subunit vaccines. The form of the vaccine antigen (e.g., soluble or particulate/aggregate) appears to play an important role in determining immunogenicity and the interactions between dendritic cells, B cells and T cells in the germinal center are likely to dictate the magnitude and duration of protective immunity. By learning how to optimize these interactions, we may be able to elicit more effective and long-lived immunity with fewer vaccinations.