Hepatitis A virus infection in households

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.

Using the power law model to predict the long-term persistence and duration of detectable hepatitis A antibody after receipt of hepatitis A vaccine (VAQTA™)

VAQTA™ (Hepatitis A Vaccine, inactivated [HAVi]; Merck & Co., Inc., Kenilworth, NJ, USA) is currently licensed for prevention of disease caused by hepatitis A virus in persons ≥12 months of age. This report summarizes statistical models developed to evaluate the long-term persistence and duration of detectable hepatitis A antibody (total antibody levels with no distinction on class) after receipt of HAVi in healthy children and adolescents (V251-023 and V251-035) and in healthy adults (V251-034). The statistical models presented, conducted separately for each of the three studies, are based on models that have been used in the literature to estimate the duration of antibody to protect against human papillomavirus (HPV) disease. In the absence of observed study data on hepatitis A antibody persistence for vaccine recipients over several decades, an extrapolation from a kinetic model of antibody decay was used to estimate the duration of detectable antibody. Extrapolation of observed antibody titers from postvaccination, Year 2.5-3.5, Year 5-6, and Year 10 in 165 children and adolescents who received HAVi at Day 0 and Week 24 in V251-023 suggests that detectable levels of antibody may persist after the second dose for many years. This model suggests that 25 to 50 years Postdose 1 in a two-dose series of HAVi, 99.4% of the study population will have detectable levels of hepatitis A antibody.

The History of Hepatitis A

Watch an interview with the author.

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.

Hepatitis A in internationally adopted children: screening for acute and previous infections

OBJECTIVE

The goal was to determine the prevalence of acute hepatitis A virus (HAV) infection and immunity among internationally adopted children.

METHODS

Children seen at the International Adoption Center between September 25, 2006, and September 30, 2008, and were screened for HAV within 4 months after their arrival in the United States were eligible for the study. The age- and country-specific prevalence of acute HAV infection and immunity were determined.

RESULTS

Overall, 288 children underwent HAV serological testing. Of the 279 with total HAV serological results, 29% had positive findings. Immunity varied according to region and country. The prevalence was lowest among children born in Asia/Pacific Rim region (17%) and highest among children born in Africa (72%). Only 13% of children <2 years of age were immune, compared with 80% of children 12 to 17 years of age (P = .002). Increasing age and birth region were associated independently with immunity. Positive HAV immunoglobulin M test results were found for 3 (1%) of 270 children; all were without symptoms. Their ages were 18, 27, and 41 months, and they were born in Kazakhstan, Russia, and the Latin America/Caribbean region, respectively. The father of 1 child developed HAV infection after arriving home.

CONCLUSIONS

HAV immunity among internationally adopted children varied according to age and country of origin; 1% had acute infections. HAV screening is useful for determination of the need for HAV immunization and for prevention of transmission to family members and close contacts.

Prophylaxie autour d'un cas index d'hépatite A: immunoglobulines ou vaccination?

France has changed from a country where hepatitis A is endemic to one where residents are at risk of hepatitis A infection: in 20 years, the seroprevalence in 20-year-olds has fallen from 50% to less than 10%. Prophylaxis for close contacts of an index case has therefore become a major problem because their risk of hepatitis A is high. Polyvalent immunoglobulins are recommended in several countries, but no immunoglobulins are approved for this indication in France. Immunoglobulins are also expensive and only slightly efficacious. A vaccine against hepatitis A administered to young children or adolescents can break the epidemic chain and protect adults very effectively by limiting virus circulation. Many countries propose early vaccination to at-risk contacts, with vaccination generally advised within a week of the initial infectious contact. Although more specific and more plentiful data are still necessary before this recommendation can be generalized, it must be taken into account. This medical decision should thus be made on an individualized basis after discussion between the physician and family about the risk.

Vaccination contre l’hépatite A : autour du cas index

The dramatic decrease in the incidence of hepatitis A in France renders routine vaccination unecessary. However, the main problem concerns prophylaxis for persons exposed to an index case, because nonspecific immunoglobulins are recommended but unavailable in France for this indication. The vaccination of persons who come into contact with an index case is possible in the days following exposure. Some data relating to exposure within the household and in small communities, including nursery schools, have been reported: immunisation in such situations is effective and recommended by the British Advisory Board in the 7 days following exposure, but not in France. The availability of this form of protection and active individual prophylaxis should be suggested to families by clinicians.

The effects of socioeconomic development on worldwide hepatitis A virus seroprevalence patterns

BACKGROUND

Hepatitis A virus (HAV) infection confers long-term immunity, so mathematical analysis of age-specific seroprevalence in populations can reveal changes in the infection rate over time. HAV transmission is related to access to clean drinking water, personal hygiene and public sanitation.

METHODS

We used an SIR (susceptible-infectious-recovered) compartmental model with age structure to fit a time-dependent logistic function for HAV force of infection for 157 published age-seroprevalence data sets. We then fit linear regression models for socioeconomic variables and infection rate.

RESULTS

The proportion of the population with access to clean drinking water, the value of the human development index (HDI), and per capita gross domestic product (GDP) are all inverse predictors of HAV infection rates. Declining infection rates were observed in 65.6% of the surveys. Discussion This work demonstrates the utility of HAV seroprevalence studies to reveal patterns of change in force of infection and to assess the association between socioeconomic risk factors and transmission rates.

Vaccination contre l'hépatite A chez l'enfant

Hepatitis A is usually considered as a mild disease and is asymptomatic in more than 80% of children less than 5 years of age. Furthermore, incidence of the disease decreased dramatically in France during the past decades. For these reasons mass routine vaccination is not required in our country. However, infected children shed the virus in the community and are responsible for secondary cases, sometimes severe. That is why, despite the cost and the absence of reimbursement of the vaccine, immunisation against hepatitis A is recommended in children attending health-care institutions, in children with chronic liver disease and in those travelling in endemic areas. Prophylaxis around an index case is the main problem because non-specific immunoglobulins, although recommended, are not available in France for this indication. Vaccination in the few days following exposition has been reported to be efficient in household contacts and small communities, including nurseries. This strategy is recommended by the British Advisory Board within the 7 days following exposition, but not in France. However, it can be proposed to the family by paediatricians.

A post-licensure evaluation of the safety of inactivated hepatitis A vaccine (VAQTA, Merck) in children and adults

BACKGROUND

Hepatitis A is a major cause of epidemic hepatitis in the US. In pre-licensure trials, inactivated hepatitis A vaccine (HAV, VAQTA, Merck) was shown to be generally well-tolerated and effective in inducing immunity to hepatitis A infection in adults and children over 2 years of age. Following the licensure of this vaccine, we began a Phase IV safety evaluation in adults and in children over 2 years of age.

METHODS

Safety was assessed by comparing the rates of diagnoses in clinic, emergency and hospital utilization. From April 1997 to December 1998, rates of diagnoses within 30 days for the clinic and emergency setting and 60 days for hospitalization were compared with unexposed follow-up time in the same individuals both before receipt of vaccine and after the 60 days interval post-vaccination.

RESULTS

There were a total of approximately 2000 comparisons between the risk and "before" or "after" period. Among them, 106 were found to have statistically significant differences in rates (30 elevated, 76 lowered). Among children/adolescents (2-17 year-old), in the hospitalization category, the only statistically significant elevated risk found was "elective procedures", as compared with both "before" and "after" periods. In the outpatient visit category for children and adolescents, elevated risks were found for consultation/general medicine/exam when compared with both "before" and "after" periods, and ganglion and viral warts when compared with either "before" or "after" period. Among adults (> or =18 year-old), in the outpatient visit category, a statistically significant elevated relative risk was seen for diarrhea/gastroenteritis for both "before" and "after" periods. There were additionally 17 diagnostic categories that showed a statistically significantly elevated relative risk compared with either "before" or "after" period. Except for diarrhea/gastroenteritis, the other eight events were elevated only in one comparison (either "before" or "after"). These eight elevated relative risks might be explained by chance resulting from multiple comparison or seasonal variations. There were no serious adverse events judged by the investigator to be associated with HAV.

CONCLUSION

In this large Phase IV evaluation of the safety of HAV, the vaccine appeared to be generally well-tolerated. These data support the continued routine use of HAV for vaccination in children and adults.

A serological study of intrafamilial spread from patients with sporadic hepatitis E virus infection

Intrafamilial transmission is rare in epidemic hepatitis E; its frequency in sporadic hepatitis E is not known. We followed up 86 household contacts (age range 4-75 years, mean +/- SD 32.4 +/- 15.8; 49 males), who were family members of patients with acute sporadic hepatitis E. Of the 86 contacts, 68 (79%) tested negative for IgG anti-hepatitis E virus antibodies. Four (4.7%) had IgM anti-hepatitis E virus antibodies at the time of diagnosis of hepatitis E in the index case; two of these contacts possibly had hepatitis E virus infection acquired simultaneously with that in the index case, and two could have had intrafamilial transmission. None developed serological evidence of hepatitis E virus infection over a period of 49 +/- 18 days after the diagnosis of index case, although a majority lacked IgG antibodies to hepatitis E virus and were likely to be susceptible. This suggests that person-to-person transmission is uncommon in sporadic hepatitis E.

Effectiveness of hepatitis A vaccine in a former frequently affected community: 9 years' followup after the Monroe field trial of VAQTA

The Kiryas Joel community in Monroe, N.Y. was the site of the first clinical trial which proved the protective efficacy of hepatitis A vaccine. The vaccine used was VAQTA J. Med. Virol (hepatitis A vaccine, inactivated). In the 9 years since the trial ended vaccination of infants reaching 2 years of age has continued along with monitoring for hepatitis A cases. The prevaccine pattern of frequent outbreaks has converted to a sustained pattern of no outbreaks, despite sporadic introduction of hepatitis A into the community in nonvaccinees. Community use of VAQTA in children 2 years of age and older has proven capable of providing long-term prevention of hepatitis A outbreaks in a formerly frequently affected community despite prolonged sporadic introduction of the virus.

Posttravel hepatitis A: probable acquisition from an asymptomatic adopted child

We report a case of acute hepatitis A in an adoptive parent that was probably acquired from a recently adopted child with asymptomatic, active infection. Prospective adoptive parents should be protected against hepatitis A because of potential exposure during travel and the risk of unrecognized active infection in adopted children.

Cost-benefit analysis of a nationwide infant immunization programme against hepatitis A in an area of intermediate endemicity

BACKGROUND/AIMS

The availability of safe and effective Hepatitis A vaccines prompts an evaluation of a nationwide infant vaccination campaign to supplement strategies aimed at high-risk groups such as travellers and military personnel.

METHODS

A spreadsheet model was used to estimate costs and benefits of a nationwide infant immunization programme against Hepatitis A for the period from 1997-2014 in Israel.

RESULTS

Immunizing all one year olds in Israel from 1997-2014 would for a cost of $32.0 million to the health services and $42.1 million to society (including $10.1 million lost work and transport costs), reduce the number of cases of Hepatitis A during the next 45 years from 181,000 to 47,000. This would save $57.5 million in health service resources alone, $32.0 million in averted work absences and transport costs in addition to a further $17.0 million in averted premature mortality costs. The health service, resource and societal benefit:cost ratios are 1.80:1, 2.13:1 and 2.54:1, respectively.

CONCLUSIONS

The recent adoption of a nationwide infant HAV immunisation policy in Israel is both medically and economically justifiable.

Hepatitis E

Hepatitis E, previously known as enterically transmitted non-A, non-B hepatitis, is an infectious viral disease with clinical and morphologic features of acute hepatitis. Its causative agent, hepatitis E virus, consists of small, 32- to 34-nm diameter, icosahedral, nonenveloped particles with a single-stranded, positive-sense, 7.5-kb RNA. The virus has two main geographically distinct strains, Asian and Mexican; recently, novel isolates from nonendemic areas and a genetically related swine HEV have been described. HEV is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in the Indian subcontinent, southeast and central Asia, the Middle East, parts of Africa, and Mexico. The virus is excreted in feces and is transmitted predominantly by fecal-oral route, usually through contaminated water. Person-to-person transmission is uncommon. Clinical attack rates are the highest among young adults. Recent evidence suggests that humans with subclinical HEV infection and animals may represent reservoirs of HEV; however, further data are needed. Diagnosis of hepatitis E is usually made by detection of specific IgM antibody, which disappears rapidly over a few months; IgG anti-HEV persists for at least a few years. Clinical illness is similar to other forms of acute viral hepatitis except in pregnant women, in whom illness is particularly severe with a high mortality rate. Subclinical and unapparent infections may occur; however, chronic infection is unknown. No specific treatment is yet available. Use of clean drinking water and proper sanitation is currently the most effective method of prevention. Passive immunization has not been proved to be effective, and recombinant vaccines for travelers to disease-endemic areas and for pregnant women currently are being developed.

Hepatitis A

Hepatitis A remains an important cause of community-acquired hepatitis in the United States and in the world. In recent years, improvements in personal hygiene and environmental sanitation have led to declines in overall hepatitis A infection rates in developed countries, although sporadic outbreaks still occur with similar rates of hospitalization and loss of work. Therapy remains supportive and prevention holds the key to elimination of widespread infection. Acute infection can be prevented or attenuated with IG or with inactivated, highly immunogenic vaccines. Elderly persons and those with advanced liver disease are at higher risk of the consequences of acute HAV, and they represent target populations for immediate vaccination. Challenges for the future include strategies for broad-based population vaccination, including cost-effective approaches.

Investigations of the epidemiology of infections with hepatitis A virus in Jamaica

Between January 1995 and August 1998, a study was conducted to elucidate the epidemiology of hepatitis A virus (HAV) in Jamaica. Participants were recruited from six sites across the island. The potential risk factors for transmission which were studied included age of the individual, gender, residence (urban v. rural area), sanitary facilities (flush toilet v. pit) and source of domestic water (indoor plumbing v. other). There were 128 male subjects and 211 female, aged 3-90 years. The mean ages of the males and females were 24.9 and 25.6 years, respectively. The seroprevalence of HAV in the study population, estimated by ELISA, was 59.9%. Logistic regression indicated that age (P < 0.001) and source of domestic water (P = 0.006) were the major contributors to exposure to HAV. The rate of exposure to the virus was seen to increase with age. By the age of 10 years, 30% of children had been exposed, and almost 100% of the oldest subjects were seropositive. Rates of exposure to HAV were higher among households which had external sources of water, including standpipes, rivers and tanks, than those with indoor plumbing. Although the seroprevalence of HAV in Jamaica is similar to that seen in developing countries, the age-related pattern of exposure mirrors the pattern seen in developed countries.

Hepatitis A antibodies in liver transplant recipients: evidence for loss of immunity posttransplantation

Liver transplant recipients frequently have chronic liver diseases and should be considered for vaccination against hepatitis A virus (HAV). However, persistence of protective antibodies after orthotopic liver transplantation (OLT) has not been shown in this population, which may have implications for future vaccine recommendations. We evaluated the prevalence and epidemiological significance of immunoglobulin G (IgG) antibody to HAV (anti-HAV) in a nonvaccinated population before OLT (immunity from previous exposure) and determined the persistence of IgG anti-HAV at 1 and 2 years after OLT. One hundred consecutive patients were identified who underwent OLT and had at least 2 years of follow-up post-OLT. They were not vaccinated against HAV infection at any time. Clinical data were summarized from medical records, and stored sera were tested for IgG anti-HAV before OLT and at 1 and 2 years after OLT by a commercially available enzyme immunoassay. Of 100 patients, 24 had IgG anti-HAV before OLT. No epidemiological differences were noted between those with or without detectable IgG anti-HAV before OLT. Among patients with detectable IgG anti-HAV before OLT, 4 of 22 patients (18%) and 7 of 24 patients (29%) became negative for IgG anti-HAV at 1 and 2 years post-OLT, respectively. None of the patients with undetectable IgG anti-HAV before OLT became positive at any time. Most of our patients with end-stage liver disease had no serological evidence for immunity against HAV. A significant proportion of patients with detectable protective antibodies before OLT lost their antibodies at 2 years after OLT.

Hepatitis E: an overview and recent advances in clinical and laboratory research

Hepatitis E virus (HEV) is a non-enveloped RNA (7.5 kb) virus that is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in southeast and central Asia, the Middle East, parts of Africa and Mexico. Hepatitis E virus infection spreads by the faecal-oral route (usually through contaminated water) and presents after an incubation period of 8-10 weeks with a clinical illness resembling other forms of acute viral hepatitis. Clinical attack rates are the highest among young adults. Asymptomatic and anicteric infections are known to occur. Chronic HEV infection is not observed. Although the mortality rate is usually low (0.07-0.6%), the illness may be particularly severe among pregnant women, with mortality rates reaching as high as 25%. Recent isolation of a swine virus resembling human HEV has opened the possibility of zoonotic HEV infection. Studies of pathogenetic events in humans and experimental animals reveal that viral excretion begins approximately 1 week prior to the onset of illness and persists for nearly 2 weks; viraemia can be detected during the late phase of the incubation period. Immunoglobulin M antibody to HEV (anti-HEV) appears early during clinical illness but disappears rapidly over a few months. Immunoglobulin G anti-HEV appears a few days later and persists for at least a few years. There is no specific treatment available for hepatitis E virus infection. Ensuring a clean drinking water supply remains the best preventive strategy. Recombinant vaccines are being developed that may be particularly useful for travellers to disease-endemic areas and for pregnant women.

Prevalence of antibodies against hepatitis A and E viruses among rural populations of the Chaco region, south-eastern Bolivia

We conducted a cross-sectional study to determine the seroprevalence of antibodies against hepatitis A and hepatitis E viruses (HAV and HEV) in the population of two rural areas, Camiri and Villa Montes, of the Chaco region, south-eastern Bolivia. HAV antibodies were detected in 461 (94.1%) of 490 serum samples tested, not differing significantly between sexes and study areas. The HAV seropositivity rate (64.7%) was high even in the youngest age group (1-5 years). The prevalence of HEV was 7.3%, with no significant differences between sexes. The prevalence of HEV antibodies in the population of the Camiri area (10.4%) was significantly higher than in the Villa Montes area (4.4%), possibly due to the better quality of drinking water in the Villa Montes area. In the population </= 30 years of age, the HEV seropositivity rate (4.4%) was significantly lower than in the >/= 31 year-old group. This is consistent with findings in other countries. This is the first report of the prevalence of HEV infection in Bolivia.

The effect of age and weight on the response to formalin inactivated, alum-adjuvanted hepatitis A vaccine in healthy adults

Formalin-inactivated, alum-adsorbed, hepatitis A vaccine was evaluated in 100 healthy adults who were stratified at enrollment into two age groups: 18-39 years: n = 50; 40-65 years: n = 50. All individuals received vaccine at 25 U of viral antigen. After stratification, both groups were randomized to receive either vaccination at 0 and 24 weeks or vaccination at 0.2 and 24 weeks. Subjects were bled for serology at 0, 2, 4, 24, 28 weeks and 1 year. The seroconversion rate and geometric mean titer (GMT = mIU ml-1) after one dose of vaccine was lower for older subjects [second week: < 40 years: 15/25 (60%) (GMT: 12.9). > 40 years: 5/22 (23%) (GMT: 6.1): fourth week: < 40 years: 20/22 (91%) (GMT: 29.0), > 40 years: 16/23 (70%) (GMT: 14.3)]. After a second dose at 2 weeks the seroresponse improved so that there were no longer differences between age groups [24 weeks: < 40: 21/22 (95%) (GMT: 123.9), > 40: 22/23 (96%) (GMT: 106.1)]. A third dose at 24 weeks resulted in a 20-40-fold increase in GMT in both age groups. As a separate evaluation height, weight, skin fold thickness, and body mass index (BMI) were assessed by logistic regression for their ability to predict serologic response. Serologic response was significantly associated with lower weight (P = 0.032) and BMI (P = 0.024) but not with height or skin fold thickness. Hepatitis A vaccine was well tolerated, with no serious adverse experiences. Adults older than 40 years appear to respond less well than younger adults to a single dose of 25 U of hepatitis A vaccine but equally well after two doses of vaccine. The slower antibody response to hepatitis A vaccine in overweight individuals was not attributable to skin adipose tissue.

Viral hepatitis in older adults

The objective of this paper is to review the epidemiology, manifestations, therapy, and prevention of viral hepatitis in older people and to discuss issues of prevention and management. In developed countries a significant portion of the adult population is not immune to Hepatitis A virus (HAV). Morbidity and mortality from HAV infection increases with age. A safe and effective hepatitis A vaccine is available and health authorities should consider immunization early in life and for healthy adults as well as for potential high risk groups such as nursing home residents. Acute hepatitis due to Hepatitis B virus (HBV) is rare in older people and is usually a mild disease. Most older patients with chronic HBV infection who suffer from advanced liver disease have no evidence of ongoing viral replication. Therefore, they are not candidates for interferon therapy. Those with evidence of ongoing viral replication and compensated liver disease should be offered interferon or be included in clinical trials with new antiviral drugs such as lamivudine. Since the response rate to hepatitis B vaccination decreases with age, developing vaccines with greater immunogenicity is crucial. Hepatitis C virus (HCV) is the most frequent cause of acute viral hepatitis in older people. Acute hepatitis C is usually a mild disease in this age group. Because many older patients with chronic HCV infection have compensated liver disease, they could benefit from antiviral therapy. In light of the low response rate to interferon in older patients with chronic hepatitis C and the side effects of the drug, interferon therapy should be reserved for those with the best chance of response. "Combination" antiviral therapy should be on trial for older patients with chronic HCV infection who do not respond to interferon. The recently discovered RNA virus, Hepatitis G (HGV), has been associated with liver disease in older people. It's role in the pathogenesis of liver injury remains to be elucidated.

Hepatitis

Hepatitis is a diagnosis that can easily be missed by the physician. The morbidity of this disease is significant when one takes into account all the cases that either do not have a typical presentation or are misdiagnosed. The emergency physician bears substantial responsibility in the diagnosis and intervention of patients with hepatitis, and needs to develop a systematic way of approaching the patient with a viral syndrome or other vague complaints that will allow appropriate consideration of this diagnosis.

Hepatitis E

Hepatitis E has a world-wide distribution and causes substantial morbidity and mortality in some developing countries, particularly among pregnant women. Hepatitis E virus (HEV) has recently been cloned and sequenced, and new diagnostic tests have been developed. These tests have been used to begin to characterize the natural history and epidemiological features of HEV infection. Experimental vaccines have also been developed that offer the potential to prevent hepatitis E. However, much remains to be learned about HEV, including the mechanisms of transmission, the reservoir(s) of the virus, and the natural history of protective immunity in order to develop effective strategies to prevent this disease.

Duration of protection from clinical hepatitis A disease after vaccination with VAQTA

Recent papers examining the expected persistence of anti-hepatitis A virus antibody following vaccination with inactivated hepatitis A vaccine have estimated that geometric mean antibody levels will remain above cut-off levels for 10-30 years. However, the methodology used in these papers did not take into account any estimates of variability between subjects. In this paper data from the persistence of antibody after the administration of another vaccine, VAQTA (hepatitis A vaccine, inactivated; MSD), were used to develop further models of antibody decay. Using individual subject estimates instead of group means allowed the estimation of time to negativity for various percentiles of the population (including the median), and the construction of confidence intervals on estimates of time to negativity. Data from studies of subjects who seroreverted to negativity, and subsequently received a booster dose, were also considered to show that subjects who lose detectable antibody are likely to remain protected from hepatitis A disease by persistent immune memory and rapid anamnestic response soon after exposure to hepatitis A virus. The estimates of duration of protection suggest that VAQTA will provide protection for many years, first through presence of antibody and further through an anamnestic response based on persistent immune memory.

Prevalence study of different hepatitis markers among pregnant Albanian refugees in Greece

Aim of the study was to record the prevalence of the various types of viral hepatitis, especially hepatitis B, in pregnant Albanian refugees in Greece. The study comprised 500 pregnant refugees of mean age 25.1 +/- 4.6 years. In Albania, all women had lived in overcrowded houses and had been exposed to non throw-away needles and syringes. Various indices for all hepatitis types were determined. The prevalence of HBsAg was 13.4%, of anti-HBs 53%, of total anti-HBc 70.8%, of anti-HBc IgM 0.4%, of HBeAg 1.2%, of anti-HBe 58.6%, of anti-HAV 96.2%, of anti-HAV IgM 1%, of anti-HDV 0.4%, of anti-HCV 0.6% and of anti-HEV 2%. HBeAg was found positive in 7.5% of HBsAg carriers. Prevalence of hepatitis B markers, as determined by HBsAg and/or anti-HBs and/or total anti-HBc was significantly higher in those with a history of previous hospitalization in Albania (p = 0.01) and those with previous history of hepatitis (p = 0.02). The high prevalence of hepatitis B markers in pregnant Albanian refugees proves that HBV infection is highly endemic in Albania and the possibility of perinatal transmission to the offsprings urges for HBV vaccination programmes. On the other hand improvements in the socioeconomic conditions and the sanitation system in Albania is anticipated to reduce the incidence of HAV and HBV infections.

Hepatitis E: an overview

Hepatitis E has a worldwide distribution and causes substantial morbidity and mortality in some developing countries, particularly among pregnant women. Hepatitis E virus (HEV) has recently been cloned and sequenced and new diagnostic tests have been developed; these tests have been used to begin to characterize the natural history and epidemiologic features of HEV infection. Experimental vaccines have also been developed that offer the potential to prevent hepatitis E. However, to develop effective strategies to prevent this disease, much remains to be learned about HEV, including the vehicles of transmission, the reservoir(s) of the virus, and the natural history of protective immunity.

Viral hepatitis. Current concepts for dental practice

The transmission of blood-borne viruses in the dental office is a potential hazard to patients and dental staff, particularly to oral and maxillofacial surgeons. Hepatitis B virus has been a recognized hazard for several years, and in the past oral surgeons and other dental health care staff have been infected as a result of occupational exposure. Hepatitis C virus in contrast does not appear to be a major occupational hazard to dental staff, nevertheless, infection with this virus can lead to significant morbidity and may have oral manifestations. Hepatitis D virus can be nosocomally transmitted, but vaccination against the hepatitis B virus minimizes this problem. Hepatitis E virus is not of clinical relevance to dentistry, although dental staff who are in areas of endemic infection can become infected as a result of enteric transmission. A number of other putative viral agents may also cause hepatitis, but additional data is awaited, and their significance to dental practice is unknown. This article summarizes current data on hepatitis viruses A, B, C, D, and E.

Immunogenicity and safety in adults of hepatitis A virus vaccine administered as a single dose with a booster 6 months later

An inactivated vaccine against hepatitis A was administered as a single 1,440 enzyme-linked immunosorbent assay (ELISA) units dose at month 0 with a booster at month 6 to 200 subjects divided into two age groups: group 1, 20-39 years (n = 134) and group II, 40-62 years (n = 66). At day 15, the seropositivity rates were 90% and 77% in groups I and II, respectively. At month 1 the seropositivity rate was 97% in both groups. At month 6 the seropositivity rates were 94% and 88% in groups I and II, respectively. One month after the booster, at month 7, 100% in both groups had become seropositive. The vaccine was well tolerated and did not cause any severe reactions. The results indicate that a single high vaccine dose offers protection against hepatitis A virus (HAV) for at least 6 months in the majority of cases where rapid vaccination is required even in travellers of older age. A booster dose will ensure long-term protection.

Should aboriginals in the "top end" of the Northern Territory be vaccinated against hepatitis A?

OBJECTIVE

To determine the level of immunity to hepatitis A virus infection in rural Australian Aboriginal populations in the "Top End" of the Northern Territory.

METHODS

A total of 344 sera, for which details of donors' age, sex and domicile were available, were collected and tested for hepatitis A total antibody in a delinked seroprevalence study.

RESULTS

Overall, 337/344 samples (97.97%) tested positive for hepatitis A total antibodies--18/20 samples (90%) in the 1-5 year age group; 85/88 (96.6%) in the 6-10 year age group; 98/98 (100%) in the 11-15 year age group; 32/33 (97.0%) in the 16-20 year age group and 104/105 (99%) in the older than 20 year age group.

CONCLUSION

Hepatitis A is hyperendemic in the rural Aboriginal communities studied and the virus is acquired predominantly in the first five years of life. Symptomatic hepatitis A infection is uncommon in this population. We suggest that hepatitis A vaccination for rural Aboriginal children is not indicated as it would not reduce clinical disease rates and may produce a cohort whose immunity could decrease over the following 10 years. Although vaccination is appropriate for non-immune individuals working in remote communities, emphasis must be placed on the inequities in health infrastructure and education underlying the high transmission rates in Aboriginal children.

The current epidemiology of hepatitis A infection in South Africa: implications for vaccination

Testing stored sera from various categories of individuals has shown that among the Black population hepatitis A virus (HAV) infection is universal and most adult Black subjects are immune. Infection probably occurs early in life, consistent with the epidemiological pattern seen in the developing world. By contrast, seroprevalence of HAV infection in adult White subjects increases with age, reflecting an epidemiological pattern seen in the developed world. White subjects working in a virological laboratory and White medical students had comparatively low seroprevalences of HAV infection and could therefore represent groups at risk. Hepatitis A vaccine is likely to be available in South Africa in the near future and could be offered to these groups. Pre-vaccination immunity screening would be a cost-effective strategy.

Inactivated hepatitis A vaccine in childhood: implications for disease control

The experience to date with the Merck inactivated hepatitis A vaccine in healthy children 2-16 years old is reviewed. Comparison of response to increasing doses indicates that an intramuscular dose of 25 units results in seroconversion of 99% of children by week 4 following a single dose. Antibody persistence rate is nearly 100% six months later, whether or not a second priming dose is given at week 8. This vaccine has proven highly immunogenic in children and has a favourable safety/tolerability profile. It should be useful for pre-exposure prophylaxis and control of hepatitis A, and should eventually replace immune globulin (Ig) for this indication.

Single and booster dose responses to an inactivated hepatitis A virus vaccine: comparison with immune serum globulin prophylaxis

Pre- and postexposure prophylaxis against hepatitis A virus (HAV) infection with immune serum globulin (Ig) is only effective for 4-6 months. We compared the safety, tolerability and immunogenicity of a single i.m. injection of Ig with a single and booster dose of an inactivated hepatitis A virus vaccine (iHAV) in adults. Healthy volunteers (18-50 years) received a single Ig i.m. injection (n = 30), or iHAV i.m. (n = 15) at 0 and 24 weeks, or placebo (n = 4) at the same intervals. Anti-HAV seroconversion was measured by radioimmunoassay (RIA) and neutralizing antibodies by an antigen reduction assay. After Ig injection (0.06 ml/kg), anti-HAV seroconversion occurred in 100% of recipients at week 1, declining to 10% at week 12 and 0% by week 20. In contrast, after a single 25 ng dose, RIA seropositivity in iHAV vaccinees was 80% by week 2, reaching 100% by week 5 and persisted up to week 24, at which time anti-HAV geometric mean titres (GMT) were two fold higher than those seen at week 1 after Ig. Postbooster anti-HAV titres in iHAV recipients rose within 4 weeks to 73-fold greater than the peak GMT seen one week after Ig, and 400-fold higher than GMT at 12 weeks after Ig. Neutralizing antibody titres after iHAV followed a similar pattern, as observed for anti-HAV. iHAV was well tolerated; placebo and vaccine tolerability were indistinguishable, with no serious adverse experiences observed. In conclusion, active vaccination with a single iHAV dose may eventually replace Ig for pre-exposure prophylaxis.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety, tolerability, and immunogenicity of an inactivated hepatitis A vaccine: effects of single and booster injections, and comparison to administration of immune globulin

Hepatitis A virus (HAV) infection in adults is often symptomatic and disabling. The present article summarizes our experience with phase 2 studies of an inactivated hepatitis A virus vaccine. Pre- and post-exposure prophylaxis with immune globulin (IG) is only effective for 4-6 months. We compared the safety, tolerability, and immunogenicity of a single i.m. injection of IG with single and booster doses of an inactivated hepatitis A virus vaccine (iHAV) in adults. A total of 75 healthy volunteers (aged 18-50 years) were evaluated in two separate studies. The first included 15 volunteers who received 25 units iHAV i.m. at 0 and 24 weeks. The second, a randomly controlled study, consisted of three groups receiving 25 units iHAV i.m. at 0, 1, and 6 months, or at 0, 2, and 6 months, or 0.06 ml/kg IG i.m. given once. Anti-HAV seroconversion was measured by radioimmunoassay (RIA). After IG injection, anti-HAV seroconversion occurred in 100% of recipients at week 1, declining to 10% at week 12, and 0% by week 20. In contrast, after a single 25-unit dose, RIA seropositivity in iHAV vaccines was 73% by week 2, reaching 100% by week 5, and persisted in all up to week 24, at which time anti-HAV geometric mean titers (GMT) were 2-fold higher than those seen at week 1 after IG. Administration of a booster dose given 1 or 2 months after primary immunization did not significantly improve the quantitative anti-HAV response at 6 months as compared to the effect of the primary dose.(ABSTRACT TRUNCATED AT 250 WORDS)

A controlled trial of a formalin-inactivated hepatitis A vaccine in healthy children

BACKGROUND

Although inactivated hepatitis A vaccine is known to be well tolerated and immunogenic in healthy children and adults, its efficacy has yet to be established.

METHODS

To evaluate the efficacy of the hepatitis A vaccine in protecting against clinically apparent disease, we conducted a double-blind, placebo-controlled trial in an Hasidic Jewish community in upstate New York that has had recurrent outbreaks of hepatitis A. At the beginning of a summer outbreak, 1037 healthy seronegative children 2 to 16 years of age were randomly assigned to receive one intramuscular injection of a highly purified, formalin-inactivated hepatitis A vaccine or placebo. A case was defined by the presence of typical signs and symptoms, a diagnostic increase in IgM antibody to hepatitis A, and a serum concentration of alanine aminotransferase at least twice the upper limit of normal. Cases occurring greater than or equal to 50 days after the injection were included in the evaluation of efficacy. The children were followed for a mean of 103 days.

RESULTS

A total of 519 children received vaccine, and 518 received placebo. The vaccine was well tolerated, with no serious adverse reactions. From day 50 after the injection, 25 cases of clinically apparent hepatitis A occurred in the placebo group and none in the vaccine group (P less than 0.001), confirming that the vaccine had 100 percent protective efficacy. Before day 21, seven cases occurred in the vaccine group and three cases in the placebo group. After that time, there were no cases among vaccine recipients and 34 cases among placebo recipients.

CONCLUSIONS

The inactivated purified hepatitis A vaccine that we tested is well tolerated, and a single dose is highly protective against clinically apparent hepatitis A.

Epidemiology of hepatitis A in Mediterranean countries

Infection with hepatitis A virus (HAV) is still endemic in some Mediterranean areas. In most Northern Mediterranean countries, the incidence of acute icteric hepatitis in adults is increasing. This is due to the shifting of HAV infection to adulthood as a result of the decline of its overall prevalence due to improvements in socioeconomic, sanitary and hygienic conditions. The majority of adults remain susceptible and develop overt disease when infected, since the severity of disease is highly associated with age. Epidemics are now rare, but are more extensive when they do occur. They may sometimes be caused by accidental contamination of the water supply, but are usually due to contamination of food by diseased food-handlers or result from contaminated frozen foods. Outbreaks still may occur in day-care centres and in schools. Thus travelling to endemic areas is becoming the main source of HAV infection. Intrafamilial person-to-person spread also is an important source of infection. Transmission from children to parents and other adults may occur due to lack of immunity in the adult population. Selective immunization would further reduce the incidence of the disease. However, only inclusion of the vaccine in the routine programme of childhood immunization would guarantee the disappearance of hepatitis A.

Safety profile and immunogenicity of an inactivated vaccine derived from an attenuated strain of hepatitis A

To determine the safety and immunogenicity of an inactivated hepatitis A vaccine, 56 healthy adult volunteers were randomly assigned to receive an intramuscular injection of 6.3, 12.5 or 25 ng of inactivated hepatitis A vaccine or placebo at 0, 2 or 4, and 24 weeks. Adverse reactions occurred with similar frequency in vaccine and placebo recipients and consisted primarily of pain or tenderness at the injection site. By 4 weeks after a single 6.3, 12.5 or 25 ng injection, seven, nine and ten out of ten vaccinees, respectively, had antibody detectable by a HAV AB assay modified to increase its sensitivity tenfold. All vaccinees had antibodies detectable by this assay within 2 weeks of their second inoculation. Geometric mean antibody levels increased with higher doses of vaccine (p = 0.05). Neutralizing antibody was detected within 4 weeks of a single inoculation in all vaccinees. Neutralizing antibody was detected after the third inoculation at dilutions of greater than or equal to 1:2048 in all 12.5 and 25 ng vaccinees. All 19 vaccinees tested at 24 months still had HAV antibodies detectable by a modified HAV AB assay. This inactivated hepatitis A vaccine appears to be well tolerated and immunogenic at doses of 6.3-25 ng. The choice of dose and vaccination schedule may depend on the rapidity with which seroconversion is desired.

Hepatitis A and B infections in Yaoundé, Cameroon

Hepatitis A and B virus infections are common in the tropics. There is, however, no information concerning hepatitis A virus (HAV) infection in Cameroon, while data on the hepatitis B virus (HBV) infection are incomplete. Sera from 272 subjects attending the Central Hospital, Yaoundé, for blood donations or mild ailments were tested by an ELISA technique for the presence of anti-HAV total antibody; antibody was found in 217 (79.8%). When 188 subjects (randomly chosen from the 272) were further tested for the presence of the hepatitis B surface antigen (HBsAg), 18 (9.6%) were positive; these included 9 of 127 males (7.1%) and 9 of 61 females (14.8%). Antibody to the HBsAg (anti-HBs) was present in 15 of 43 persons (34.9%) who were HBsAg-seronegative, while antibody to the hepatitis B core antigen was detected in 76 of 97 subjects (78.4%) who had been seronegative to the HBsAg and had not been tested for anti-HBs. Thus, 60% of our subjects (including 45% of subjects under five years of age) had at least one marker indicative of previous infection with the hepatitis B virus.

Shifts in the rates and levels of antibody to hepatitis A virus associated with hepatitis A infection in children's communities

In order to investigate the shift in the rates and levels of antibody to hepatitis A virus, 567 children in 20 isolated groups of five day-care centers were observed over a period of 8 months during which the seasonal rise in hepatitis A morbidity occurs. Increases in the proportion of seropositive ranging from 5 to 37% were demonstrated in 6 groups, and were always associated with the occurrence of either overt or sub-clinical hepatitis A infection. High rates of seropositivity were also noted in the groups in which cases of hepatitis A had been registered prior to the period of observation. In some children with low and medium antibody levels, antibody titres showed further increases after reinfection. A substantial part of children retained low antibody titres during the entire period of observation, and eight previously sero-negative children developed low antibody levels after asymptomatic hepatitis A infections. In one group the spread of hepatitis A infection (clinical and asymptomatic) was prevented by the administration of commercially available immunoglobulin immediately after the discovery of an infected food handler. Passive antibodies were found in previously sero-negative children, and these antibodies dropped to undetectable levels two months after administration.

Neutralizing antibody to hepatitis A virus in immune serum globulin and in the sera of human recipients of immune serum globulin

We determined the titer of neutralizing antibody to hepatitis A virus in five lots of immune serum globulin and in the sera of human recipients of immune globulin using a new and sensitive procedure, the radioimmunofocus inhibition assay. The neutralizing antibody titer of four immune globulin lots ranged from 1:170,000 to 1:406,000, and was approximately 100-fold the antibody titer determined by radioimmunoassay. The neutralizing antibody titer of a Bureau of Biologics reference immunoglobulin was 1:794,000. Sera collected from 18 healthy men who had undergone prophylaxis with immune globulin (0.02 ml/kg body wt) were negative when tested by radioimmunoassay. However, 2 of 18 sera collected before administration of immune globulin and sera from all 18 men collected 3 and 55 days later contained detectable neutralizing antibody. The measurement of neutralizing antibody should prove useful for standardizing passive immunoprophylaxis against hepatitis A as well as for evaluating the potential efficacy of new hepatitis A virus vaccines.

Serological hepatitis A virus infections and ratio of clinical to serological infections in a controlled trial of pre-exposure prophylaxis with immune serum globulin

Seroconversion to hepatitis A virus was studied in a sub sample of 802 Israeli military recruits (611 men and 191 women) who were taking part in a randomised controlled trial of pre-exposure immune serum globulin (ISG) for the prevention of viral hepatitis. On intake into the service 35% of the men and 47% of the women were negative to hepatitis. A virus antibody (anti-HAV). After three years 7 of 71 men (9.9%) who had not received pre-exposure ISG had become positive to anti-HAV compared to 2 of 83 (2.4%) who had received it; the statistical significance of this difference was p = 0.052. At two years 2 of 30 women (6.7%) who had not received ISG had converted compared to 1 of 43 (2.3%) who had received ISG (p = 0.37). Pooling the sexes gave conversion rates of 8.9% in those not immunised and 2.4% in those immunised (p = 0.029). The sex adjusted odds ratio was 4.0 (95% confidence limits 1.3-19.0). The morbidity rates for clinical non B hepatitis over the three year period among 12 835 men were 7.2 per 1000 in those not immunised and 3.6 per 1000 in those immunised (p = 0.004). Point estimates of the ratio of clinical hepatitis to seroconversion in men ranged from 0.25 to 0.30. It is concluded that pre-exposure administration of ISG effectively prevented clinical expression of viral hepatitis, apparently reduced seroconversion, and did not induce passive-active immunisation.