Hepatitis A virus infections in the United States: model-based estimates and implications for childhood immunization

Cost-effective analysis of hepatitis A vaccination in Kerala state, India

Several hepatitis A outbreaks have recently been reported in Kerala state, India. To inform coverage decision of hepatitis A vaccine in Kerala, this study aimed to examine the cost-effectiveness of 1) hepatitis A vaccination among children aged 1 year and individuals aged 15 years, and 2) serological screening of individuals aged 15 years and vaccination of susceptible as compared to no vaccination or vaccination without serological screening. Both live attenuated hepatitis A vaccine and inactivated hepatitis A vaccine were considered in the analysis. A combination of decision tree and Markov models with a cycle length of one year was employed to estimate costs and benefits of different vaccination strategies. Analysis were based on both societal and payer perspectives. The lifetime costs and outcomes were discounted by 3%. Our findings indicated that all strategies were cost-saving for both societal and payer perspectives. Moreover, budget impact analysis revealed that vaccination without screening among individuals aged 15 years could save the government's budget by reducing treatment cost of hepatitis A. Our cost-effectiveness evidence supports the inclusion of hepatitis A vaccination into the vaccination program for children aged 1 year and individuals aged 15 years in Kerala state, India.

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.

Treatment Options for Hepatitis A and E: A Non-Systematic Review

Hepatitis A and hepatitis E are relatively common causes of liver disease. Both viruses are mainly transmitted through the faecal-oral route and, consequently, most outbreaks occur in countries with poor sanitation. An important role of the immune response as the driver of liver injury is also shared by the two pathogens. For both the hepatitis A (HAV) and hepatitis E (HEV) viruses, the clinical manifestations of infection mainly consist of an acute disease with mild liver injury, which results in clinical and laboratory alterations that are self-limiting in most cases. However, severe acute disease or chronic, long-lasting manifestations may occur in vulnerable patients, such as pregnant women, immunocompromised individuals or those with pre-existing liver disease. Specifically, HAV infection rarely results in fulminant hepatitis, prolonged cholestasis, relapsing hepatitis and possibly autoimmune hepatitis triggered by the viral infection. Less common manifestations of HEV include extrahepatic disease, acute liver failure and chronic HEV infection with persistent viraemia. In this paper, we conduct a non-systematic review of the available literature to provide a comprehensive understanding of the state of the art. Treatment mainly consists of supportive measures, while the available evidence for aetiological treatment and additional agents in severe disease is limited in quantity and quality. However, several therapeutic approaches have been attempted: for HAV infection, corticosteroid therapy has shown outcome improvement, and molecules, such as AZD 1480, zinc chloride and heme oxygenase-1, have demonstrated a reduction in viral replication in vitro. As for HEV infection, therapeutic options mainly rely on the use of ribavirin, and some studies utilising pegylated interferon-alpha have shown conflicting results. While a vaccine for HAV is already available and has led to a significant reduction in the prevalence of the disease, several vaccines for HEV are currently being developed, with some already available in China, showing promising results.

Clinical, serological and epidemiological features of hepatitis A in León, Nicaragua

BACKGROUND AND OBJECTIVES

To monitor and document the endemicity and disease burden of acute hepatitis A in the area of an ongoing vaccine effectiveness study in León, Nicaragua.

METHODS

At community health centres in León, all children, adolescents and young adults presenting with jaundice and/or other clinical signs of hepatitis were offered free serologic screening (hepatitis A, B and C) and blood tests for liver enzymes and bilirubin. Clinical and socioeconomic data were collected with a structured questionnaire. Diagnosis of acute hepatitis A was confirmed by anti-HAV IgM testing. Using logistic regression we compared the characteristics and living conditions of acute hepatitis A cases with those of non-cases.

RESULTS

Of 557 eligible subjects enrolled between May 2006 and March 2010, 315 (56.6%) were diagnosed with hepatitis A, 80.6% of them ≤10 years and five >18 years of age. No severe cases were encountered. Apart from jaundice (95.6%) and other signs of hepatitis A (fever, pale stool, dark urine, nausea, vomiting, anorexia), two thirds of patients had moderately raised liver enzymes. Cases occurred throughout the year, with highest incidences from August to March. Poor sanitary conditions and crowding were the main risk factors.

CONCLUSIONS

In the study area, hepatitis A is still highly endemic in young and school age children living in low socioeconomic conditions. There are, however, first indications that the endemicity level is shifting from high to high-intermediate.

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.

Epidemiological investigation on hepatitis A virus infection outbreak in the area of Rzeszow city during the years 2017/18

Aim of the study

To define the threats and epidemiological differences between outbreaks of hepatitis A (HA) in adults and children, and to assess the efficiency of implemented prophylaxis. We also present a summary of treatment and sick leave costs as compared to the predicted money-load in the case of properly initiated prophylaxis in hepatitis A virus (HAV)-exposed persons.

Material and methods

The cause of two outbreaks was contamination related to food mishandling by a person infected with HAV. Especially health-threatening was exposure to the infection of 137 pre-school children. A second outbreak caused by the same source was observed among 25 exposed adults. On the basis of medical documentation we determined costs related to hospitalization and sickness leave absence at work, comparing it with money load related to implementation of required prophylaxis in both groups of people exposed to risk of HAV infection.

Results

As a consequence of exposure in the kindergarten area, an infection was confirmed in 32 patients from the first and subsequent generations and 7 cases were observed in the second outbreak. Costs of hospitalization and related to the sick leave were estimated to double the predicted costs of prophylaxis.

Conclusions

In the case of lack of proper hand hygiene of a food handler with HA or in the case of food-borne exposure of children to HAV it is necessary to apply post-exposure prophylaxis. Costs of the prophylaxis are significantly lower than costs of HA. Both outbreaks underwent self-limitation with longer course of morbidity and larger number in the case of the kindergarten focus.

Rapid Salivary IgG Antibody Screening for Hepatitis A

Hepatitis A virus (HAV) is a common infection that is transmitted through the fecal-oral route, shed in the stool of infected individuals, and spread either by direct contact or by ingesting contaminated food or water. Each year, approximately 1.4 million acute cases are reported globally with a major risk factor for exposure being low household socioeconomic status. Recent trends show a decrease in anti-HAV antibodies in the general population, with concomitant increases in the numbers of HAV outbreaks. In line with a recreational water study, this effort aims to assess the prevalence of salivary IgG antibodies against HAV and subsequent incident infections (or immunoconversions) in visitors to a tropical beach impacted by a publicly owned treatment works (POTW). We applied a multiplex immunoassay to serially collected saliva samples gathered from study participants who recreated at Boquerón Beach, Puerto Rico. Analysis of assay results revealed an immunoprevalence rate of 16.17% for HAV with 1.43% of the cohort immunoconverting to HAV. Among those who immunoconverted, 10% reported chronic gastrointestinal symptoms and none experienced diarrhea. Tests on water samples indicated good water quality with low levels of fecal indicator bacteria; however, the collection and analysis of saliva samples afforded the ability to detect HAV infections in beachgoers. This rapid assay serves as a cost-effective tool for examining exposure to environmental pathogens and can provide critical information to policy makers, water quality experts, and risk assessment professionals seeking to improve and protect recreational water and public health.

Bayesian modelling of a hepatitis A outbreak in men who have sex with men in Sydney, Australia, 1991/1992

To control hepatitis A spread by vaccination, accurate estimation of transmissibility is vital. Regan et al. (2016) proposed a model of hepatitis A virus (HAV) transmission and used least squares to calibrate model to the 1991/1992 HAV outbreak in men who have sex with men (MSM) in Sydney, Australia. Based on the estimate of R₀, they obtained the critical immunity of 70% and showed that when the proportion immune <70%, there is a definite chance for outbreaks to take place. The immunity level from previous surveys ranges from 32% to 64% after 1996 while no outbreaks in Australian MSMs have been reported since 1996. Further noticing the ill-distributed parameters, we argue that their estimate of R₀ is not accurate. In this study, we revisited their model by Bayesian inference, which has privilege over least squares. We obtained the appropriate posterior distributions of parameters and the estimate of R₀ ranges from 1.38 to 2.89, indicating a critical immunity of 65%. The reduction in critical immunity and outbreak probabilities predicts the absence of outbreaks in Australian MSMs since 1996. Our study shows the importance of using appropriate methods to provide reliable and accurate estimates of the model parameters especially the transmissibility.

Prevalence of viral and non-viral hepatitis in Menoua Division, West Region, Cameroon: a retrospective hospital-based study

Introduction

The paucity of data on hepatitis' epidemiology in Menoua Division, west region, Cameroon, prompted us to assess the prevalence of viral and non-viral hepatitis in this area.

Methods

A retrospective exhaustive study based on records of patients from January 2008 to June 2014 was conducted in 9 health centres in Menoua Division. Targeted subjects were patients who did not receive hepatitis vaccines for the past year and have been screened for hepatitis B virus (HBV), hepatitis C virus (HCV) and/or a blood transaminase. Associations between variables were quantified with odd ratios (OR) and 95% confidence interval (CI). Cochran-Armitage test of linear trend was used for testing proportions of ordinal variables. Fisher's exact test was used for testing the association between 2 qualitative variables when expected counts were less than 5.

Results

The overall prevalence were 9.6% and 6.7% for HBV and HCV respectively. HBV mostly infected people aged 21-30 (12.4%) while the prevalence of HCV increased with age up to 35.4% (p=0.03). A 0.6% co-infection was observed. Thirty percent of positive HBV or HCV had high transaminase while 13% of patients with elevated transaminase showed negative viral serology.

Conclusion

These results show that hospital-based prevalence of HCV and HBV in Menoua Division is under the Cameroon's national range but point out the fact that non-viral hepatitis might be a serious case of concern in this area. There is therefore, a need to identify the risk-factors of non-viral hepatitis.

Analysis of genetic and serology of hepatitis A virus infection during and after outbreak in two junior high schools in Surabaya, Indonesia

Outbreaks of hepatitis A have occurred in some cities in Indonesia. In Surabaya, the capital city of East Java province, Indonesia, hepatitis A outbreaks have been reported since2013, with a marked increase in the number of cases in 2015. The aim of the present study was to analyze the genetic and serology of acute symptomatic cases (early infection) during a hepatitis A outbreak and asymptomatic cases after the outbreak in two junior high schools in Surabaya in 2015 to 2016. Students with acute symptomatic hepatitis A during the outbreak and other students who were asymptomatic 3 to 4 months after the outbreak were enrolled. Asymptomatic students had no symptoms from the outbreak until they were enrolled. Sera were collected to identify anti-hepatitis A virus (HAV) IgM (by enzyme-linked immunosorbent assay) and HAV genetic variations/genotypes (using polymerase chain reaction [PCR]-sequencing and phylogenetic analysis). A total of 33 (97.1%) out of 34 sera of students with acute symptoms were positive for anti-HAV IgM and 18% of them were positive by PCR, identified as HAV subgenotype IA. No prominent amino acid variations were observed from reported HAV sequences from Indonesia. Among 38 sera of asymptomatic students, most (55.3%) were positive for anti-HAV IgM, while none were positive by PCR. In conclusion, HAV-IA was the only subgenotype identified in acute symptomatic cases during the outbreak. The percentage of HAV-specific IgM-positive cases was very high among acute symptomatic students, but that was also high among asymptomatic students, which might contribute as the important source of infection during the outbreak.

Modelling the decline and future of hepatitis A transmission in Australia

Hepatitis A incidence has declined in most countries through a combination of prevention measures, augmented through the use of a highly effective vaccine. In Australia, the proportion of the population susceptible to hepatitis A infection has declined over time due to high rates of opportunistic vaccination as well as the sustained inflow of seropositive immigrants from high-endemicity countries. These factors have contributed to a rapid decline in incidence. An age-structured hepatitis A transmission model incorporating demographic changes was fitted to seroprevalence and disease notification data and used to project incidence trends and transmission potential for hepatitis A in the general population. Robustness of findings was assessed through worst-case scenarios regarding vaccine uptake, migration and the duration of immunity. The decline in age-specific seroprevalence until the introduction of hepatitis A vaccine in 1994 was well explained through a declining basic reproduction number (R₀ ) that remained >1. Accounting for existing immunity, we estimated that the effective reproduction number (R_eff ) <1 in the general population of Australia since the early 1990s, declining more rapidly after the introduction of the hepatitis A vaccine. Future projections under a variety of scenarios support R_eff remaining <1 with continued low incidence in the general population. In conclusion, our results suggest that sustained endemic transmission in the general Australian population is no longer possible although risks of sporadic outbreaks remain. This suggests potential for local elimination of hepatitis A infection in Australia, provided that elimination criteria can be defined and satisfied in risk groups. The methodology used here to investigate elimination potential can easily be replicated in settings such as in the USA where sequential seroprevalence studies are supported by routine notification data.

Hepatitis A surveillance: sensitivity of two information sources

BACKGROUND

The frequency of mild forms of hepatitis A, especially in children, could lead to underreporting. The objective of the study was to investigate the sensitivity of two surveillance systems, mandatory Statutory Disease Reports and the Microbiological Reporting System of Catalonia, using capture-recapture techniques.

METHODS

The study was conducted in Catalonia between 2011 and 2015. Hepatitis A cases reported to two independent surveillance systems were included: Statutory Disease Reports (SDR) and Microbiological Reporting System of Catalonia (MRS). The variables collected were: age, sex, year of declaration, size of municipality (< 10,000 and ≥ 10,000), country of birth (Spain or abroad), reporting centre (primary care/hospital) and notification method (electronic or paper). The capture-recapture analysis and the estimate of 95% confidence intervals were made using the Chapman formula for comparison of two sources, both for the estimate of the total number of cases and the stratification according to variables. Multinomial logistic regression was performed to obtain an adjusted estimate.

RESULTS

The SDR had a greater overall sensitivity than the MRS (48.8%; 43.5-55.6 vs. 19.3%; 17.2-21.9). In cases aged < 15 years the sensitivity of both systems was higher (76.6%; 72.7-81 vs. 25.2%; 20.9-29.5) than in cases aged > 15 years (25.5%; 22.8-28.3 vs. 12.1%; 10-14.2). For those born in Spain, the sensitivity was 57.2% (49.6-67.4) in the SDR and 27.1% (23.5-31.9) in the MRS, lower than that for foreign-born patients (58%; 51.2-66.8 vs. 49.1%; 43.4-56.6). In electronically-reported cases, the sensitivity was much higher in the SDR than in the MRS (47.2%; 42.3-52.1 vs. 9.4%; 6.5-12.3). No differences were observed according to sex, size of municipality, and year of declaration or reporting centre. The estimated total number of cases using the Chapman formula was very similar to the adjusted estimate (1121; 985-1258 vs. 1120; 876-1525), indicating the robustness of the results.

CONCLUSIONS

The sensitivity of the SDR was greater than that of MRS, especially in patients aged < 15 years, although for patients born abroad the difference in sensitivity was lower. Reinforced surveillance combining the SDR and MRS improves the efficiency in the detection of cases.

Safety and immunogenicity of VAQTA® in children 12-to-23 months of age with and without administration of other US pediatric vaccines

Safety and immunogenicity data from 5 clinical trials conducted in the US in children 12-to-23 months old where HAVi was administered alone or concomitantly with other pediatric vaccines (M-M-R®II, Varivax®, TRIPEDIA®, Prevnar®, ProQuad®, PedvaxHIB®, and INFANRIX®) were combined. Among 4,374 participants receiving ≥ 1 dose of HAVi, 4,222 (97%) had safety follow-up and the proportions reporting adverse events (AE) were comparable when administered alone (69.4%) or concomitantly with other pediatric vaccines (71.1%). The most common solicited injection-site AEs were pain/tenderness (Postdose 1: 25.8%; Postdose 2: 26.1%) and redness (Postdose 1: 13.6%; Postdose 2: 15.1%). The most common vaccine-related systemic AEs were fever (≥ 100.4ºF, 12.2%) and irritability (8.1%). Serious AEs (SAEs) were observed at a rate of 0.4%; 0.1% were considered vaccine-related. No deaths were reported within 14 days following a dose of HAVi. These integrated analyses also showed that protective antibody concentrations were elicited in 100% of toddlers after two doses and 92% after a single dose, regardless of whether HAVi was given concomitantly with other vaccines or alone. These results demonstrate that HAVi was well-tolerated whether given alone or concomitantly with other vaccines, with a low incidence of vaccine-related SAEs. HAVi was immunogenic in this age group regardless of whether administered with or without other pediatric vaccines and whether 1 or 2 doses were administered. HAVi did not impact the immune response to other vaccines. These data continue to support the routine use of HAVi with other pediatric vaccines in children ≥ 12 months of age.

Distribution of hepatitis A antibodies in US blood donors

BACKGROUND

Recently, there has been an increase in the number of hepatitis A outbreaks in the United States. Although the presence of hepatitis A virus (HAV) RNA in blood donors is known to be low, HAV antibody prevalence in this population is unknown.

STUDY DESIGN AND METHODS

Samples from 5001 US blood donors collected primarily in the midwestern United States in 2015 were tested for the presence of HAV IgG antibodies using chemiluminescent microparticle immunoassays on the ARCHITECT platform (Abbott Laboratories).

RESULTS

The overall prevalence of IgG anti-HAV was 60%. Only one specimen was IgM anti-HAV positive, for an incidence of 0.02%. IgG anti-HAV prevalence among donors aged 16 to 19 years was 67%, decreased to 54% among donors aged 40 to 49 years and increased to 70% among donors aged 80 to 93 years. No differences were seen by sex with overall IgG anti-HAV prevalence of 61% and 60% for males and females, respectively. Among the five states (Illinois, Indiana, Kansas, Kentucky, and Missouri) with the highest number of donors tested, IgG anti-HAV prevalence in Missouri (65%) was significantly higher (p <0.01) than that in Illinois (52%) or Kentucky (59%). No other significant differences between states were noted.

CONCLUSION

This study demonstrates the overall high rates of IgG anti-HAV in US blood donors, with the low associated risk of HAV transfusion transmission likely the result of low incidence and effective vaccination.

Estimating human-to-human transmissibility of hepatitis A virus in an outbreak at an elementary school in China, 2011

Hepatitis A is caused by hepatitis A virus and occurs worldwide. Estimating the transmissibility, which is usually characterized by the basic reproductive number R₀, the mean number of secondary infectious cases generated by a single primary infectious case introduced into a totally susceptible population, provides crucial information for the effort required to stop infection spreading. Hepatitis A virus is usually transmitted indirectly through contaminated food and environment. An outbreak from March to June 2011 was reported to have occurred at an elementary school of 698 pupils in China and it was found that the outbreak was due to direct transmission between school children. Based on the symptom onset date and the social contact network of the children, in this study we estimate the serial interval (i.e. the gap in symptom onset between an infectee and its infector) and use different statistical methods to estimate R₀. Combining with the positivity of IgG antibodies tests, we develop a compartmental transmission dynamics model which includes both asymptomatic and symptomatic infections to estimate the overall R₀. Our analysis suggests a serial interval of mean = 23.9 days and standard deviation = 20.9 days. The different statistical methods suggest estimates for R₀ in the outbreak varying from 2.1 to 2.8, and the estimates from the transmission dynamics model are consistent with this range. Our estimates are in agreement with that from one study in England but are higher than that from one study in the United States. Our transmission dynamics model suggests that the proportion of symptomatic infections is about 9%, implying that there were about 344 asymptomatic infections along with the 32 observed symptomatic cases. Furthermore, it is shown that the inclusion of asymptomatic infection in the epidemic process increases the estimate of R₀ but does not do so greatly provided that the proportion of symptomatic infections is constant over the outbreak and there is no difference in transmissibility between symptomatic and asymptomatic infections.

Natural History, Clinical Manifestations, and Pathogenesis of Hepatitis A

Hepatitis A virus (HAV) is transmitted by the fecal-oral route and is a major cause of acute viral hepatitis. The clinical manifestations of HAV infection range from asymptomatic infection to acute liver failure (ALF), but do not include progression to chronic hepatitis. Risk factors for severe acute hepatitis A are older age (>40 years) and preexisting liver disease. Some patients may show atypical clinical features such as relapsing hepatitis, prolonged cholestasis, or extrahepatic manifestations. Almost all hepatitis A patients spontaneously recover with supportive care. However, in the case of ALF (<1%), intensive care and urgent decision on liver transplantation are required. Liver injury during hepatitis A is not directly caused by HAV but is known to be caused by immune-mediated mechanisms. In this review, the natural history and clinical manifestations of hepatitis A are described. In addition, mechanisms of immunopathogenesis in hepatitis A are discussed.

Relationship of Severity of Hepatitis A with Polymorphisms in Hepatitis A Virus Cellular Receptor 1 (HAVCR1) Gene

INTRODUCTION AND AIM

HAVCR1 protein is the cellular receptor for hepatitis A virus (HAV). Genetic polymorphism in this gene may alter the outcome of HAV infection. In a previous study, a 6-amino acid insertion (157insMTTTVP) in HAVCR1 gene was associated with more severe disease. We decided to investigate this association further.

MATERIAL AND METHODS

We sequenced exon 4 of the HAVCR1 gene in patients with clinical hepatitis A attending our institution, and a group of healthy controls in a disease-endemic setting in India. Frequencies of different haplotypes of a genomic region with two overlapping insertion-deletion polymorphisms (indels; rs141023871 and rs139041445) were compared between patients and controls, as well as between patients with and without a severe form of disease (liver failure).

RESULTS

The gene had three haplotypes in the region of interest - a short form, an intermediate-form with a 5-amino acid 157insMTTVP insertion and a long-form with a 6-amino acid 157insMTTTVP insertion. The allele frequency (29/150 [19%] vs. 43/146 [29%]; p = ns) and haplotype frequency (29/75 [39%] vs. 39/73 [53%]; p = ns) of the 157insMTTTVP variant were similar in hepatitis A patients and healthy controls (30%). Further, the allele frequency (12/58 [21%] vs. 17/92 [18%]; p = ns) and haplotype frequency (12/29 [41%] vs.17/46 [37%]; p = ns) of the longest variant were also similar in patients with severe and mild disease.

DISCUSSION

In the study population, the 157insMTTTVP variant of HAVCR1 gene was not associated with more severe outcome of HAV infection. Further studies in other populations around the world are needed to assess the relation of this genetic variation with disease outcome.

Public health impact and cost effectiveness of routine childhood vaccination for hepatitis a in Jordan: a dynamic model approach

Background

As the socioeconomic conditions in Jordan have improved over recent decades the disease and economic burden of Hepatitis A has increased. The purpose of this study is to assess the potential health and economic impact of a two-dose hepatitis A vaccine program covering one-year old children in Jordan.

Methods

We adapted an age-structured population model of hepatitis A transmission dynamics to project the epidemiologic and economic impact of vaccinating one-year old children for 50 years in Jordan. The epidemiologic model was calibrated using local data on hepatitis A in Jordan. These data included seroprevalence and incidence data from the Jordan Ministry of Health as well as hospitalization data from King Abdullah University Hospital in Irbid, Jordan. We assumed 90% of all children would be vaccinated with the two-dose regimen by two years of age. The economic evaluation adopted a societal perspective and measured benefits using the quality-adjusted life-year (QALY).

Results

The modeled vaccination program reduced the incidence of hepatitis A in Jordan by 99%, 50 years after its introduction. The model projected 4.26 million avoided hepatitis A infections, 1.42 million outpatient visits, 22,475 hospitalizations, 508 fulminant cases, 95 liver transplants, and 76 deaths over a 50 year time horizon. In addition, we found, over a 50 year time horizon, the vaccination program would gain 37,502 QALYs and save over $42.6 million in total costs. The vaccination program became cost-saving within 6 years of its introduction and was highly cost-effective during the first 5 years.

Conclusion

A vaccination program covering one-year old children is projected to be a cost-saving intervention that will significantly reduce the public health and economic burden of hepatitis A in Jordan.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3034-8) contains supplementary material, which is available to authorized users.

Quantifying the population effects of vaccination and migration on hepatitis A seroepidemiology in Australia

Since licensure of hepatitis A vaccine in Australia in 1994, infection rates have declined to record lows. Cross-sectional serosurveys conducted over this period meanwhile have shown rising population immunity, particularly in young to middle-aged Australians. In this study, we performed a retrospective birth cohort analysis to estimate the contributions of infection, migration and vaccination towards increased levels of age specific hepatitis A seroprevalence in Australia. When aggregated across age, we find that two-thirds of the increase in population seropositivity (67.04%) between 1994 and 2008 was due to vaccination, just under one-third due to migration, with a negligible contribution from infection (<1%). Comparisons with other data sources reflecting vaccine uptake suggest the magnitude of this effect is realistic. We suggest that these results primarily relate to opportunistic vaccination and indicate the level of population immunity achievable through opportunistic programs providing further evidence for policy considerations around universal hepatitis A vaccine recommendations.

Modeling the hepatitis A epidemiological transition in Brazil and Mexico

BACKGROUND

Many low- to middle-income countries have completed or are in the process of transitioning from high or intermediate to low endemicity for hepatitis A virus (HAV). Because the risk of severe hepatitis A disease increases with age at infection, decreased incidence that leaves older children and adults susceptible to HAV infection may actually increase the population-level burden of disease from HAV. Mathematical models can be helpful for projecting future epidemiological profiles for HAV.

METHODS

An age-specific deterministic, dynamic compartmental transmission model with stratification by setting (rural versus urban) was calibrated with country-specific data on demography, urbanization, and seroprevalence of anti-HAV antibodies. HAV transmission was modeled as a function of setting-specific access to safe water. The model was then used to project various HAV-related epidemiological outcomes in Brazil and in Mexico from 1950 to 2050.

RESULTS

The projected epidemiological outcomes were qualitatively similar in the 2 countries. The age at the midpoint of population immunity (AMPI) increased considerably and the mean age of symptomatic HAV cases shifted from childhood to early adulthood. The projected overall incidence rate of HAV infections decreased by about two thirds as safe water access improved. However, the incidence rate of symptomatic HAV infections remained roughly the same over the projection period. The incidence rates of HAV infections (all and symptomatic alone) were projected to become similar in rural and urban settings in the next decades.

CONCLUSION

This model featuring population age structure, urbanization and access to safe water as key contributors to the epidemiological transition for HAV was previously validated with data from Thailand and fits equally well with data from Latin American countries. Assuming no introduction of a vaccination program over the projection period, both Brazil and Mexico were projected to experience a continued decrease in HAV incidence rates without any substantial decrease in the incidence rates of symptomatic HAV infections.

Health economic assessment of universal immunization of toddlers against Hepatitis A Virus (HAV) in Mexico

Hepatitis A virus (HAV) has shifted from high to intermediate endemicity in Mexico, which may increase the risk of clinically significant HAV infections in older children, adolescents and adults. The objective of this study was to evaluate the cost-utility of single-dose or 2-dose universal infant HAV vaccination strategy in Mexico, compared with no vaccination. A previously published dynamic model estimated the expected number of HAV cases with each strategy, and a decision model was used to estimate the costs and quality-adjusted life-years (QALYs) expected with each strategy. The time horizon was 25 years (2012–2036) and the base case analysis was conducted from the perspective of the Mexican public health system. Costs and QALYs after the first year were discounted at 5% annually. Input data were taken from national databases and published sources where available. The single-dose HAV vaccination strategy had an incremental cost-utility ratio (ICUR) of Mexican peso (MXN) 2,270 per QALY gained, compared with no vaccination. The two-dose strategy had an ICUR of MXN 14,961/QALY compared with no vaccination, and an ICUR of MXN 78,280/QALY compared with the single-dose strategy. The estimated ICURs were below the threshold of 1 x Mexican gross domestic product per capita. When indirect costs were included (societal perspective), the single-dose HAV vaccination strategy would be expected to improve health outcomes and to be cost-saving. This analysis indicates that routine vaccination of toddlers against HAV would be cost-effective in Mexico using either a single-dose or a 2-dose vaccination strategy. GSK study identifier: HO-12-12877.

The global burden of viral hepatitis from 1990 to 2013: findings from the Global Burden of Disease Study 2013

BACKGROUND

With recent improvements in vaccines and treatments against viral hepatitis, an improved understanding of the burden of viral hepatitis is needed to inform global intervention strategies. We used data from the Global Burden of Disease (GBD) Study to estimate morbidity and mortality for acute viral hepatitis, and for cirrhosis and liver cancer caused by viral hepatitis, by age, sex, and country from 1990 to 2013.

METHODS

We estimated mortality using natural history models for acute hepatitis infections and GBD's cause-of-death ensemble model for cirrhosis and liver cancer. We used meta-regression to estimate total cirrhosis and total liver cancer prevalence, as well as the proportion of cirrhosis and liver cancer attributable to each cause. We then estimated cause-specific prevalence as the product of the total prevalence and the proportion attributable to a specific cause. Disability-adjusted life-years (DALYs) were calculated as the sum of years of life lost (YLLs) and years lived with disability (YLDs).

FINDINGS

Between 1990 and 2013, global viral hepatitis deaths increased from 0·89 million (95% uncertainty interval [UI] 0·86-0·94) to 1·45 million (1·38-1·54); YLLs from 31·0 million (29·6-32·6) to 41·6 million (39·1-44·7); YLDs from 0·65 million (0·45-0·89) to 0·87 million (0·61-1·18); and DALYs from 31·7 million (30·2-33·3) to 42·5 million (39·9-45·6). In 2013, viral hepatitis was the seventh (95% UI seventh to eighth) leading cause of death worldwide, compared with tenth (tenth to 12th) in 1990.

INTERPRETATION

Viral hepatitis is a leading cause of death and disability worldwide. Unlike most communicable diseases, the absolute burden and relative rank of viral hepatitis increased between 1990 and 2013. The enormous health loss attributable to viral hepatitis, and the availability of effective vaccines and treatments, suggests an important opportunity to improve public health.

FUNDING

Bill & Melinda Gates Foundation.

Cost-effectiveness analysis of catch-up hepatitis A vaccination among unvaccinated/partially-vaccinated children

BACKGROUND

Since 2006, the US Centers for Disease Control and Prevention has recommended hepatitis A (HepA) vaccination routinely for children aged 12-23months to prevent hepatitis A virus (HAV) infection. However, a substantial proportion of US children are unvaccinated and susceptible to infection. We present results of economic modeling to assess whether a one-time catch-up HepA vaccination recommendation would be cost-effective.

METHODS

We developed a Markov model of HAV infection that followed a single cohort from birth through death (birth to age 95years). The model compared the health and economic outcomes from catch-up vaccination interventions for children at target ages from two through 17years vs. outcomes resulting from maintaining the current recommendation of routine vaccination at age one year with no catch-up intervention.

RESULTS

Over the lifetime of the cohort, catch-up vaccination would reduce the total number of infections relative to the baseline by 741 while increasing doses of vaccine by 556,989. Catch-up vaccination would increase net costs by $10.2million, or $2.38 per person. The incremental cost of HepA vaccine catch-up intervention at age 10years, the midpoint of the ages modeled, was $452,239 per QALY gained. Across age-cohorts, the cost-effectiveness of catch-up vaccination is most favorable at age 12years, resulting in an Incremental Cost-Effectiveness Ratio of $189,000 per QALY gained.

CONCLUSIONS

Given the low baseline of HAV disease incidence achieved by current vaccination recommendations, our economic model suggests that a catch-up vaccination recommendation would be less cost-effective than many other vaccine interventions, and that HepA catch-up vaccination would become cost effective at a threshold of $50,000 per QALY only when incidence of HAV rises about 5.0 cases per 100,000 population.

Hepatitis A: epidemiology in resource-poor countries

PURPOSE OF REVIEW

Transmission of hepatitis A virus (HAV) infection is primarily fecal-oral. Symptomatic hepatitis, severe disease, and death are more likely to occur when infection occurs at an older age. Improvements in socioeconomic and hygienic conditions have led to a change in its epidemiology worldwide.

RECENT FINDINGS

In the last two decades, improved hygiene in several resource-poor countries has led to reduced transmission of HAV, an increase in average age at infection, and, consequently, a paradoxical increase in morbidity and mortality because of hepatitis A. In Argentina, introduction of one dose (instead of the conventional two doses, to reduce costs) of inactivated HAV vaccine at 12-month age in a universal childhood immunization program during such 'epidemiologic transition' has markedly reduced the incidence of symptomatic hepatitis A, and of fulminant hepatitis and liver transplantation caused by HAV infection. The monetary value of medical and nonmedical benefits of this strategy outweighed the expenditure on vaccination. These excellent results were possibly contingent upon a high vaccination coverage.

SUMMARY

Resource-poor countries should closely monitor the epidemiology of HAV infection and periodically undertake cost-effectiveness analyses of HAV immunization strategies. This should allow timely identification of epidemiologic transition and introduction of preventive strategies before HAV infection becomes a public health problem.

Progress Toward Eliminating Hepatitis A Disease in the United States

Hepatitis A virus (HAV) disease disproportionately affects adolescents and young adults, American Indian/Alaska Native and Hispanic racial/ethnic groups, and disadvantaged populations. During 1996-2006, the Advisory Committee on Immunization Practices (ACIP) made incremental changes in hepatitis A (HepA) vaccination recommendations to increase coverage for children and persons at high risk for HAV infection. This report examines the temporal association of ACIP-recommended HepA vaccination and disparities (on the absolute scale) in cases of HAV disease and on seroprevalence of HAV-related protection (measured as antibody to HAV [anti-HAV]). ACIP-recommended childhood HepA vaccination in the United States has eliminated most absolute disparities in HAV disease by age, race/ethnicity, and geographic area with relatively modest ≥1-dose and ≥2-dose vaccine coverage. However, the increasing proportion of cases of HAV disease among adults with identified and unidentified sources of exposure underscores the importance of considering new strategies for preventing HAV infection among U.S. adults. For continued progress to be made toward elimination of HAV disease in the United States, additional strategies are needed to prevent HAV infection among an emerging population of susceptible adults. Notably, HAV infection remains endemic in much of the world, contributing to U.S. cases through international travel and the global food economy.

Modeling the hepatitis A epidemiological transition in Thailand

BACKGROUND

In most low- and middle-income countries, hepatitis A virus (HAV) is shifting or expected to shift from high endemicity to intermediate or low endemicity. A decreased risk of HAV infection will cause an increase in the average age at infection and will therefore increase the proportion of infections that results in severe disease. Mathematical models can provide insights into the factors contributing to this epidemiological transition.

METHODS

An MSLIR compartmental dynamic transmission model stratified by age and setting (rural and urban) was developed and calibrated with demographic, environmental, and epidemiological data from Thailand. HAV transmission was modeled as a function of urbanization and access to clean drinking water. The model was used to project various epidemiological measures.

RESULTS

The age at midpoint of population immunity remains considerably younger in rural areas than in urban areas. The mean age of symptomatic hepatitis A infection in Thailand has shifted from childhood toward early adulthood in rural areas and is transitioning from early adulthood toward middle adulthood in urban areas. The model showed a significant decrease in incidence rates of total and symptomatic infections in rural and urban settings in Thailand over the past several decades as water access has increased, although the overall incidence rate of symptomatic HAV is projected to slightly increase in the coming decades.

CONCLUSIONS

Modeling the relationship between water, urbanization, and HAV endemicity is a novel approach in the estimation of HAV epidemiological trends and future projections. This approach provides insights about the shifting HAV epidemiology and could be used to evaluate the public health impact of vaccination and other interventions in a diversity of settings.

Hepatitis E virus infections in children age 0-15, Uganda outbreak, 2007

BACKGROUND

The epidemiology of hepatitis E virus (HEV) infections among children is not well understood, with some studies reporting that hepatitis E infections do not affect children.

OBJECTIVES

We analyzed seroepidemiologic data collected during a hepatitis E outbreak in Uganda to determine prevalence of past and recent HEV infections among children aged 0-15 years.

STUDY DESIGN

Individuals were randomly selected from a household census to participate in a seroprevalence survey. We analyzed data on IgM and IgG antibody to HEV among children aged 0-15 years. We categorized the study population by age group [aged 0-5, 6-10, and 11-15 years], and further stratified the youngest children [aged 0-1, 2-3, and 4-5 years]. Presence of IgG anti-HEV alone indicated past HEV infection, whereas recent infection was defined as presence of IgM anti-HEV with or without IgG anti-HEV.

RESULTS

Among children aged 0-15 years (N=244), prevalence of past HEV infection was 25.4% (62/244) and was highest among children aged 0-5 years [31.0% (27/87)]. Evidence of recent HEV infection was detected in 37.3% (91/244) of children aged 0-15 years. Among younger children, recent HEV infection increased with age from 4.3% (1/23) in children aged 0-1 year to 36.7% (11/30) in children aged 4-5 years.

CONCLUSION

These data show that children are not spared from HEV infections. Illness during childhood in developing countries is common and HEV infections may be misdiagnosed as another acute illness, or under diagnosed. The lack of clinical care, HEV diagnostics, and surveillance in developing countries limit our full understanding of hepatitis E epidemiology.

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.

Computational modeling of interventions and protective thresholds to prevent disease transmission in deploying populations

Military personnel are deployed abroad for missions ranging from humanitarian relief efforts to combat actions; delay or interruption in these activities due to disease transmission can cause operational disruptions, significant economic loss, and stressed or exceeded military medical resources. Deployed troops function in environments favorable to the rapid and efficient transmission of many viruses particularly when levels of protection are suboptimal. When immunity among deployed military populations is low, the risk of vaccine-preventable disease outbreaks increases, impacting troop readiness and achievement of mission objectives. However, targeted vaccination and the optimization of preexisting immunity among deployed populations can decrease the threat of outbreaks among deployed troops. Here we describe methods for the computational modeling of disease transmission to explore how preexisting immunity compares with vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions. These methods are illustrated with five modeling case studies for separate diseases common in many parts of the world, to show different approaches required in varying epidemiological settings.

Modelling the force of infection for hepatitis A in an urban population-based survey: a comparison of transmission patterns in Brazilian macro-regions

Background

This study aimed to identify the transmission pattern of hepatitis A (HA) infection based on a primary dataset from the Brazilian National Hepatitis Survey in a pre-vaccination context. The national survey conducted in urban areas disclosed two epidemiological scenarios with low and intermediate HA endemicity.

Methods

A catalytic model of HA transmission was built based on a national seroprevalence survey (2005 to 2009). The seroprevalence data from 7,062 individuals aged 5–69 years from all the Brazilian macro-regions were included. We built up three models: fully homogeneous mixing model, with constant contact pattern; the highly assortative model and the highly assortative model with the additional component accounting for contacts with infected food/water. Curves of prevalence, force of infection (FOI) and the number of new infections with 99% confidence intervals (CIs) were compared between the intermediate (North, Northeast, Midwest and Federal District) and low (South and Southeast) endemicity areas. A contour plot was also constructed.

Results

The anti- HAV IgG seroprevalence was 68.8% (95% CI, 64.8%–72.5%) and 33.7% (95% CI, 32.4%–35.1%) for the intermediate and low endemicity areas, respectively, according to the field data analysis. The models showed that a higher force of infection was identified in the 10- to 19-year-old age cohort (∼9,000 infected individuals per year per 100,000 susceptible persons) in the intermediate endemicity area, whereas a higher force of infection occurred in the 15- to 29-year-old age cohort (∼6,000 infected individuals per year per 100,000 susceptible persons) for the other macro-regions.

Conclusion

Our findings support the shift of Brazil toward intermediate and low endemicity levels with the shift of the risk of infection to older age groups. These estimates of HA force of infection stratified by age and endemicity levels are useful information to characterize the pre-vaccination scenario in Brazil.

Economic evaluation of the routine childhood immunization program in the United States, 2009

OBJECTIVES

To evaluate the economic impact of the 2009 routine US childhood immunization schedule, including diphtheria and tetanus toxoids and acellular pertussis, Haemophilus influenzae type b conjugate, inactivated poliovirus, measles/mumps/rubella, hepatitis B, varicella, 7-valent pneumococcal conjugate, hepatitis A, and rotavirus vaccines; influenza vaccine was not included.

METHODS

Decision analysis was conducted using population-based vaccination coverage, published vaccine efficacies, historical data on disease incidence before vaccination, and disease incidence reported during 2005 to 2009. Costs were estimated using the direct cost and societal (direct and indirect costs) perspectives. Program costs included vaccine, administration, vaccine-associated adverse events, and parent travel and work time lost. All costs were inflated to 2009 dollars, and all costs and benefits in the future were discounted at a 3% annual rate. A hypothetical 2009 US birth cohort of 4,261,494 infants over their lifetime was followed up from birth through death. Net present value (net savings) and benefit-cost ratios of routine childhood immunization were calculated.

RESULTS

Analyses showed that routine childhood immunization among members of the 2009 US birth cohort will prevent ∼42,000 early deaths and 20 million cases of disease, with net savings of $13.5 billion in direct costs and $68.8 billion in total societal costs, respectively. The direct and societal benefit-cost ratios for routine childhood vaccination with these 9 vaccines were 3.0 and 10.1.

CONCLUSIONS

From both direct cost and societal perspectives, vaccinating children as recommended with these vaccines results in substantial cost savings.

Measuring underreporting and under-ascertainment in infectious disease datasets: a comparison of methods

BACKGROUND

Efficient and reliable surveillance and notification systems are vital for monitoring public health and disease outbreaks. However, most surveillance and notification systems are affected by a degree of underestimation (UE) and therefore uncertainty surrounds the 'true' incidence of disease affecting morbidity and mortality rates. Surveillance systems fail to capture cases at two distinct levels of the surveillance pyramid: from the community since not all cases seek healthcare (under-ascertainment), and at the healthcare-level, representing a failure to adequately report symptomatic cases that have sought medical advice (underreporting). There are several methods to estimate the extent of under-ascertainment and underreporting.

METHODS

Within the context of the ECDC-funded Burden of Communicable Diseases in Europe (BCoDE)-project, an extensive literature review was conducted to identify studies that estimate ascertainment or reporting rates for salmonellosis and campylobacteriosis in European Union Member States (MS) plus European Free Trade Area (EFTA) countries Iceland, Norway and Switzerland and four other OECD countries (USA, Canada, Australia and Japan). Multiplication factors (MFs), a measure of the magnitude of underestimation, were taken directly from the literature or derived (where the proportion of underestimated, under-ascertained, or underreported cases was known) and compared for the two pathogens.

RESULTS

MFs varied between and within diseases and countries, representing a need to carefully select the most appropriate MFs and methods for calculating them. The most appropriate MFs are often disease-, country-, age-, and sex-specific.

CONCLUSIONS

When routine data are used to make decisions on resource allocation or to estimate epidemiological parameters in populations, it becomes important to understand when, where and to what extent these data represent the true picture of disease, and in some instances (such as priority setting) it is necessary to adjust for underestimation. MFs can be used to adjust notification and surveillance data to provide more realistic estimates of incidence.

Hepatitis A and considerations regarding the cost-effectiveness of vaccination programs

Hepatitis A vaccines have demonstrated a high degree of immunogenicity and an excellent safety profile. Immunization of certain populations and patient subgroups is recommended according to specific epidemiological and clinical factors, such as a greater likelihood of acquisition of infection or concerns regarding the risk of development of fulminant hepatitis and death. Therefore, the economic implications of routine and/or targeted vaccination programs in the general population and high-risk individuals have been examined. In this manuscript, the available data from the literature regarding the cost-effectiveness of hepatitis vaccination programs in healthy individuals and in those with chronic liver disease are reviewed.

Incidence and prevalence of Toxoplasma gondii infection in women in France, 1980–2020: model-based estimation

Toxoplasmosis is a worldwide zoonosis due to Toxoplasma gondii, a ubiquitous protozoan parasite of warm-blooded animals including humans. In pregnant women, primary infection can cause congenital toxoplasmosis resulting in severe malformations in the newborn. Since 1978, public health authorities in France have implemented a congenital toxoplasmosis prevention programme, including monthly serological screening of all seronegative pregnant women, and treatment in case of seroconversion. However, this programme does not produce systematic surveillance data on incidence and prevalence. Our objective was to estimate the incidence and prevalence of T. gondii infection, and the incidence of seroconversion during pregnancy in women in France. We used a catalytic model to estimate incidence and prevalence of Toxoplasma infection between 1980 and 2020 in women of childbearing age. We used age- and time-specific seroprevalence data obtained from the National Perinatal Surveys (NPS) conducted in 1995, 2003 and 2010. We assumed that incidence depends both on age and calendar time, and can be expressed as the product of two unknown functions. We also estimated incidence of seroconversion during pregnancy in 2010 from the NPS and the National Surveillance of Congenital Toxoplasmosis (ToxoSurv). We combined data of 42208 women aged 15–45 years with serology available from the three NPS. For women aged 30 years the modelled incidence decreased from 7·5/1000 susceptible women in 1980 to 3·5/1000 in 2000. In 2010 the incidence was 2·4/1000. The predicted incidence and prevalence for 2020 was 1·6/1000 and 27%, respectively. The incidence of seroconversion during pregnancy in 2010 was estimated at 2·1/1000 susceptible pregnant women (95% CI 1·3–3·1) from the NPS and 1·9 (95% CI 1·8–2·1) from ToxoSurv. Incidence and prevalence of Toxoplasma infection has decreased markedly during the last 30 years. This decrease may be explained by a lower exposure to the parasite by changes in food habits and by improved hygiene practices in meat production. Modelled estimations were consistent with estimates observed in other studies conducted previously in France. The catalytic modelling provides reliable estimates of incidence and prevalence of Toxoplasma infection over time. This approach might be useful for evaluating preventive programme for toxoplasmosis.

Economic evaluations of hepatitis A vaccination in middle-income countries

Economic evaluations of hepatitis A vaccination are important to assist national and international policy makers in different jurisdictions on making effective decisions. Up to now, a comprehensive review of the potential health and economic benefits on hepatitis A vaccination in middle-income countries (MICs) has not been performed yet. In this study, we reviewed the literature on the cost-effectiveness of hepatitis A vaccination in MICs. Most of the studies confirmed that hepatitis A vaccination was cost effective or even cost saving under certain conditions. We found that vaccine price, medical costs, incidence and discount rate were the most influential parameters on the sensitivity analyses. Vaccine price has been shown as a barrier for MICs in implementing universal vaccination of hepatitis A. Given their relatively limited financial resources, implementation of single-dose vaccination could be considered. Despite our findings, we argue that further economic evaluations in MICs are still required in the near future.

Hepatitis A vaccination coverage among adults 18-49 years traveling to a country of high or intermediate endemicity, United States

BACKGROUND

Since 1996, hepatitis A vaccine (HepA) has been recommended for adults at increased risk for infection including travelers to high or intermediate hepatitis A endemic countries. In 2009, travel outside the United States and Canada was the most common exposure nationally reported for persons with hepatitis A virus (HAV) infection.

OBJECTIVE

To assess HepA vaccination coverage among adults 18-49 years traveling to a country of high or intermediate endemicity in the United States.

METHODS

We analyzed data from the 2010 National Health Interview Survey (NHIS), to determine self-reported HepA vaccination coverage (≥1 dose) and series completion (≥2 dose) among persons 18-49 years who traveled, since 1995, to a country of high or intermediate HAV endemicity. Multivariable logistic regression and predictive marginal analyses were conducted to identify factors independently associated with HepA vaccine receipt.

RESULTS

In 2010, approximately 36.6% of adults 18-49 years reported traveling to high or intermediate hepatitis A endemic countries; among this group unadjusted HepA vaccination coverage was 26.6% compared to 12.7% among non-travelers (P-values<0.001) and series completion were 16.9% and 7.6%, respectively (P-values<0.001). On multivariable analysis among all respondents, travel status was an independent predictor of HepA coverage and series completion (both P-values<0.001). Among travelers, HepA coverage and series completion (≥2 doses) were higher for travelers 18-25 years (prevalence ratios 2.3, 2.8, respectively, P-values<0.001) and for travelers 26-39 years (prevalence ratios 1.5, 1.5, respectively, P-value<0.001, P-value=0.002, respectively) compared to travelers 40-49 years. Other characteristics independently associated with a higher likelihood of HepA receipt among travelers included Asian race/ethnicity, male sex, never having been married, having a high school or higher education, living in the western United States, having greater number of physician contacts or receipt of influenza vaccination in the previous year. HepB vaccination was excluded from the model because of the significant correlation between receipt of HepA vaccination and HepB vaccination could distort the model.

CONCLUSIONS

Although travel to a country of high or intermediate hepatitis A endemicity was associated with higher likelihood of HepA vaccination in 2010 among adults 18-49 years, self-reported HepA vaccination coverage was low among adult travelers to these areas. Healthcare providers should ask their patients' upcoming travel plans and recommend and offer travel related vaccinations to their patients.

Effects of an ageing population and the replacement of immune birth cohorts on the burden of hepatitis A in the Netherlands

BACKGROUND

In populations in which the incidence of hepatitis A virus (HAV) infection has declined due to socio-economic improvements, better sanitation and hygiene, and vaccination, birth cohorts who have long-term immunity through exposure early in life are now being replaced by non-immune cohorts, meaning that more cases in the elderly may occur in future. Our goal was to qualitatively investigate the interaction of this cohort effect and demographic change (population ageing) on the estimated disease burden of HAV infection in the Netherlands.

METHODS

We used dynamic MSIR (maternal immunity-susceptible-infectious-recovered) transmission and demographic models to simulate annual HAV incidence over the period 2000-2030, and estimated disease burden using the disability-adjusted life years (DALY) measure and a pre-defined disease progression model. Five scenarios representing different force of infection situations were simulated.

RESULTS

The overall disease burden was projected to decrease over the simulation period in the baseline scenario (310 DALYs in 2000 compared with 67 in 2030). This decreasing trend was absent for the 55+ years age group; 23.5% of all new infections were predicted to occur in the 55+ group in 2030, compared with 5.5% in the 55+ group in 2000.

CONCLUSIONS

In the absence of further public health interventions and under the assumption of a continued steady decline in the force of infection, the HAV disease burden in the Netherlands is predicted to decrease over the coming decades, but with proportionally more of the burden occurring within the increasingly larger segment of the population represented by elderly persons who are no longer naturally immune.

Cost-effectiveness analysis of universal childhood hepatitis A vaccination in Brazil: regional analyses according to the endemic context

OBJECTIVE

To conduct a cost-effectiveness analysis of a universal childhood hepatitis A vaccination program in Brazil.

METHODS

An age and time-dependent dynamic model was developed to estimate the incidence of hepatitis A for 24 years. The analysis was run separately according to the pattern of regional endemicity, one for South+Southeast (low endemicity) and one for the North+Northeast+Midwest (intermediate endemicity). The decision analysis model compared universal childhood vaccination with current program of vaccinating high risk individuals. Epidemiologic and cost estimates were based on data from a nationwide seroprevalence survey of viral hepatitis, primary data collection, National Health Information Systems and literature. The analysis was conducted from both the health system and societal perspectives. Costs are expressed in 2008 Brazilian currency (Real).

RESULTS

A universal immunization program would have a significant impact on disease epidemiology in all regions, resulting in 64% reduction in the number of cases of icteric hepatitis, 59% reduction in deaths for the disease and a 62% decrease of life years lost, in a national perspective. With a vaccine price of R$16.89 (US$7.23) per dose, vaccination against hepatitis A was a cost-saving strategy in the low and intermediate endemicity regions and in Brazil as a whole from both health system and society perspective. Results were most sensitive to the frequency of icteric hepatitis, ambulatory care and vaccine costs.

CONCLUSIONS

Universal childhood vaccination program against hepatitis A could be a cost-saving strategy in all regions of Brazil. These results are useful for the Brazilian government for vaccine related decisions and for monitoring population impact if the vaccine is included in the National Immunization Program.

Changes in seroprevalence to hepatitis A in Victoria, Australia: a comparison of three time points

Serological data provide an important measure of past exposure and immunity to hepatitis A virus (HAV) infection in a population. National serosurveys from developed countries have typically indicated a decline in HAV seroprevalence over time as sanitation levels improve. We examined trends in the seroepidemiology of HAV antibodies in Victoria, Australia, drawing on cross-sectional samples taken at three time points over a 20-year period. Stored sera from 1988 (n=753), 1998 (n=1091), and 2008 (n=791) from persons aged 1-69 years were obtained from the state of Victoria, Australia. The within-year population adjusted results show a significant trend of increasing population HAV seroprevalence over time from 34.3% (95% CI 31.7-36.9) in 1988, to 40.0% (95% CI 37.1-42.8) in 1998 and 55.1% (95% CI 52.1-58.1) in 2008, P<0.0001. A particularly noticeable rise in population seroprevalence was observed between 1998 and 2008 for those aged 5-39 years. The increase in HAV seropositivity over time is in contrast to the declining rates of disease notification in Australia. Based on comparisons with other Australian data, it appears the increase in population seroprevalence over the last two decades is unlikely to be due to endemic transmission of infection. Instead, other factors, including increases in travel to HAV endemic regions, migration to Australia from HAV endemic regions and vaccine uptake are more likely causes. Ongoing monitoring of serological HAV profiles in the population is required to determine future policy direction to prevent increased burden.

Model-based projections of the population-level impact of hepatitis A vaccination in Mexico

There are indications of a shift in the pattern of hepatitis A (HAV) in Mexico from high to intermediate endemicity, progressively increasing the mean age of infection and the proportion of cases which are symptomatic. This study estimated the potential impact of universal infant HAV vaccination in Mexico with two doses of Havrix™ at 12 and 18 mo of age on all HAV infections and symptomatic HAV infections. We developed a dynamic transmission model that accounts for changes in demography and HAV epidemiology. It was calibrated using Mexican age-specific seroprevalence and symptomatic HAV incidence data. With 70% first-dose coverage and 85% second-dose coverage, the calibrated model projected that HAV vaccination would reduce the incidence of all HAV infections (symptomatic and asymptomatic) after the first 25 y of vaccination by 71-76% (minimum and maximum for different transmission scenarios). The projected reduction in cumulative incidence of symptomatic HAV infections over the first 25 y of vaccination was 45-51%. With 90% first-dose coverage and 85% second-dose coverage, the projected reduction in incidence of all HAV infections was 85-93%, and the projected reduction in the cumulative incidence of symptomatic HAV infections was 61-67%, over a 25-y time frame. Sensitivity analyses indicated that second-dose coverage is important under the conservative base-case assumptions made about the duration of vaccine protection. The model indicated that universal infant HAV vaccination could substantially reduce the burden of HAV disease in Mexico.

Persistence of hepatitis A vaccine induced seropositivity in infants and young children by maternal antibody status: 10-year follow-up

Persistence of seropositivity conferred by hepatitis A vaccine administered to children <2 years of age is unknown and passively transferred maternal antibodies to hepatitis A virus (maternal anti-HAV) may lower the infant's immune response to the vaccine. One hundred ninety-seven infants and young children were randomized into three groups to receive a two-dose hepatitis A vaccine: group 1 at 6 and 12 months, group 2 at 12 and 18 months, and group 3 at 15 and 21 months of age. Within each group, infants were randomized by maternal anti-HAV status. Anti-HAV levels were measured at 1 and 6 months and at 3, 5, 7, and 10 years after the second dose of hepatitis A vaccination. Children in all groups had evidence of seroprotection (>10 mIU/mL) at 1 month after the second dose. At 10 years, all children retained seroprotective anti-HAV levels except for only 7% and 11% of children in group 1 born to anti-HAV-negative and anti-HAV-positive mothers, respectively, and 4% of group 3 children born to anti-HAV-negative mothers. At 10 years, children born to anti-HAV-negative mothers in group 3 had the highest geometric mean concentration (GMC) (97 mIU/mL; 95% confidence interval, 71-133 mIU/mL) and children born to anti-HAV-positive mothers in group 1 had the lowest GMC (29 mIU/mL; 95% confidence interval, 20-40 mIU/mL). Anti-HAV levels through 10 years of age correlated with initial peak anti-HAV levels (tested at 1 month after the second dose).

CONCLUSION

The seropositivity induced by hepatitis A vaccine given to children <2 years of age persists for at least 10 years regardless of presence of maternal anti-HAV.

The global burden of hepatitis E virus genotypes 1 and 2 in 2005

We estimated the global burden of hepatitis E virus (HEV) genotypes 1 and 2 in 2005. HEV is an emergent waterborne infection that causes source-originated epidemics of acute disease with a case fatality rate thought to vary by age and pregnancy status. To create our estimates, we modeled the annual disease burden of HEV genotypes 1 and 2 for 9 of 21 regions defined for the Global Burden of Diseases, Injuries, and Risk Factors Study (the GBD 2010 Study), which represent 71% of the world's population. We estimated the seroprevalence of anti-HEV antibody and annual incidence of infection for each region using data from 37 published national studies and the DISMOD 3, a generic disease model designed for the GBD Study. We converted incident infections into three mutually exclusive results of infection: (1) asymptomatic episodes, (2) symptomatic disease, and (3) death from HEV. We also estimated incremental cases of stillbirths among infected pregnant women. For 2005, we estimated 20.1 (95% credible interval [Cr.I.]: 2.8-37.0) million incident HEV infections across the nine GBD Regions, resulting in 3.4 (95% Cr.I.: 0.5-6.5) million symptomatic cases, 70,000 (95% Cr.I.: 12,400-132,732) deaths, and 3,000 (95% Cr.I.: 1,892-4,424) stillbirths. We estimated a probability of symptomatic illness given infection of 0.198 (95% Cr.I.: 0.167-0.229) and a probability of death given symptomatic illness of 0.019 (95% Cr.I.: 0.017-0.021) for nonpregnant cases and 0.198 (95% Cr.I.: 0.169-0.227) for pregnant cases.

CONCLUSION

The model was most sensitive to estimates of age-specific incidence of HEV disease.

Determinants of anti-hepatitis A antibody seroprevalence in 2- to 19-year-olds in the USA using NHANES 2007–2008

The aim of the study was to describe the epidemiology and determinants of anti-hepatitis A seroprevalence in 2- to 19-year-olds in the USA for 2007–2008. This study was conducted in a sample of 2621 individuals aged 2–19 years in the USA using data from National Health and Nutrition Examination Survey (NHANES) 2007–2008. The overall seroprevalence of anti- hepatitis A virus (HAV) in this population was 39% (95% confidence interval 32·6–45·3). HAV seroprevalence was higher in Mexican Americans than other ethnic groups, in younger persons, and in those who reported previous vaccination compared to those who did not. We concluded that anti-hepatitis A seroprevalence rates are increasing in younger individuals in the USA, indicating a shift of seroprevalence over time due to vaccination status. Findings are consistent with a persistent influx of infection through international travel and migration and highlight the need to discern hepatitis A infection from vaccination status when assessing the effectiveness of vaccination using seroprevalence data.

Contributions from the systematic review of economic evaluations: the case of childhood hepatitis A vaccination in Brazil

The aim of this study was to present the contributions of the systematic review of economic evaluations to the development of a national study on childhood hepatitis A vaccination. A literature review was performed in EMBASE, MEDLINE, WOPEC, HealthSTAR, SciELO and LILACS from 1995 to 2010. Most of the studies (8 of 10) showed favorable cost-effectiveness results. Sensitivity analysis indicated that the most important parameters for the results were cost of the vaccine, hepatitis A incidence, and medical costs of the disease. Variability was observed in methodological characteristics and estimates of key variables among the 10 studies reviewed. It is not possible to generalize results or transfer epidemiological estimates of resource utilization and costs associated with hepatitis A to the local context. Systematic review of economic evaluation studies of hepatitis A vaccine demonstrated the need for a national analysis and provided input for the development of a new decision-making model for Brazil.

Hepatitis A antibody seroprevalence among medical school students

A total of 324 first- to third-year medical school students were examined for anti-hepatitis A virus IgG. Of these 324 students, 37 were found to be anti-hepatitis A virus IgG positive (11.4%). Mass screening of medical students for seropositivity and vaccination of nonimmune students should be considered before starting medical clerkships.

Lifecourse infectious origins of sexual inequalities in central adiposity

BACKGROUND

Social disparities in obesity are often more marked among women than men, possibly due to social factors. Taking a life-history perspective, we hypothesized that childhood infections could be relevant via sex-specific effects of immune system activation on sexual development and, hence, body shape.

METHODS

We used multivariable linear regression to assess the sex-specific, adjusted associations of 'childhood' pathogens [0 (n = 1002), 1 (n = 2199), 2 (n = 3442) or 3 (n = 4833) of HSV1, CMV and hepatitis A antibodies] and 'adult' pathogens [0 (n = 5836), 1 (n = 3018) or ≥ 2 (n = 720) of HSV2, HHV8 and hepatitis B or C) with waist-hip ratio (WHR) and body mass index (BMI) standard deviations (SDs) using NHANES III (1988-94). As validation, we assessed associations with height.

RESULTS

'Childhood' pathogens were positively associated with WHR among women [0.18 SD, 95% confidence interval (95% CI) 0.04-0.32 for 3, compared with 0], but not men (-0.04 SD, 95% CI -0.15 to 0.08), adjusted for age, education, race/ethnicity, smoking and alcohol. Further adjustments for leg length barely changed the estimates. There were no such sex-specific associations for BMI or for adult pathogens. 'Childhood', but not 'adult', pathogens were negatively associated with height, adjusted for age, sex, education and race/ethnicity.

CONCLUSIONS

These observations are consistent with the lifecourse hypothesis that early exposure to infections makes women vulnerable to central obesity. This hypothesis potentially sheds new light on the developmental origins of obesity, and is consistent with the generally higher levels of central obesity among women than men in developing populations.