Introduction

Abstract

Acute viral hepatitis is 1 of the most common infectious diseases worldwide. In 2003, approximately 61,000 individuals were newly infected with hepatitis A virus (HAV) and 73,000 individuals with hepatitis B virus (HBV) in the United States.1Centers for Disease Control and Prevention. Disease burden from viral hepatitis A, B, and C in the United States. Available at: http://www.cdc.gov/ncidod/diseases/hepatitis/resource/pdfs/disease_burden2004.pdf. Accessed May 17, 2005.Google Scholar Yet hepatitis A and B are preventable diseases. Vaccines against hepatitis B and A have been available in the United States since 1981 and 1995, respectively, and recommendations from the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) to vaccinate adults at high risk have been in place since the introduction of these vaccines.2Centers for Disease Control and PreventionPrevention of hepatitis A through active or passive immunization recommendations of the Advisory Committee on Immunization Practices (ACIP).MMWR Recomm Rep. 1996; 45 ([published erratum in: MMWR Morb Mortal Wkly Rep. 1997;46:588]): 1-30Google Scholar, 3Centers for Disease Control and PreventionRecommendation of the Immunization Practices Advisory Committee (ACIP) inactivated hepatitis B virus vaccine.MMWR Morb Mortal Wkly Rep. 1982; 31 (327–328): 317-322PubMed Google Scholar Despite these recommendations, current estimates of vaccine coverage in groups at high risk are modest, and thus HAV and HBV infections continue to result in substantial morbidity, mortality, and economic burden.Hepatitis AHepatitis A is caused by infection with HAV. The incubation period of HAV is 15 to 50 days, with a mean of approximately 30 days.4Centers for Disease Control and PreventionHepatitis A.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 177-189Google Scholar In infected persons, HAV replicates in the liver, is excreted in bile, and is shed in the stool. Peak infectivity occurs during the 2 weeks before onset of jaundice or elevation of serum liver enzymes, when the concentration of virus in stool is highest (Figure 1).5Centers for Disease Control and Prevention, National Center for Infectious Diseases. Viral hepatitis slide set. Epidemiology and prevention of viral hepatitis A to E: an overview—hepatitis A with notes. Available at: http://www.cdc.gov/ncidod/diseases/hepatitis/slideset/index.htm. Accessed June 22, 2005.Google Scholar The concentration of virus in stool declines after jaundice appears. Children may excrete virus for longer periods than do adults. Viremia occurs soon after infection and persists through the period of serum liver enzyme (alanine aminotransferase) elevation.The clinical course of hepatitis A typically begins with an abrupt onset of fever, malaise, anorexia, nausea and vomiting, abdominal pain, and dark urine. Children aged <6 years are often asymptomatic; however, symptomatic illness with jaundice occurs in >70% of older children and adults.4Centers for Disease Control and PreventionHepatitis A.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 177-189Google Scholar Although most patients recover within 2 months, each year approximately 100 persons die of fulminant hepatitis in the United States.4Centers for Disease Control and PreventionHepatitis A.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 177-189Google Scholar The case-fatality rate is highest among older persons (>49 years). Other complications of HAV infection, although uncommon, include cholestatic hepatitis and relapsing hepatitis.6Koff R.S. Hepatitis A.Lancet. 1998; 341: 1643-1649Abstract Full Text Full Text PDF Scopus (244) Google ScholarTransmission of HAV generally occurs via the fecal-oral route. Close personal contact is the most common mode of HAV transmission, as demonstrated by infections among household and sex contacts of persons with hepatitis A and among children in day care center outbreaks. Contaminated food and water also can serve as vehicles of HAV transmission. HAV transmission can occur as a result of blood exposure, such as injection drug use, although screening of blood products for HAV has essentially eliminated the already extremely low risk associated with blood transfusion.4Centers for Disease Control and PreventionHepatitis A.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 177-189Google Scholar, 6Koff R.S. Hepatitis A.Lancet. 1998; 341: 1643-1649Abstract Full Text Full Text PDF Scopus (244) Google ScholarHepatitis BHBV infection is an established cause of acute and chronic hepatitis and cirrhosis. In addition, HBV causes ≤80% of hepatocellular carcinomas. Worldwide, >200 million persons are carriers of chronic HBV infection, with >1 million carriers in the United States.7Centers for Disease Control and PreventionHepatitis B.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 191-212Google Scholar After a person is infected with HBV, the first detectable serum marker is hepatitis B surface antigen (HBsAg), which generally precedes clinical symptoms by 1 to 2 months (Figure 2).8Centers for Disease Control and Prevention, National Center for Infectious Diseases. Viral hepatitis slide set. Epidemiology and prevention of viral hepatitis A to E: an overview—hepatitis B with notes. Available at: http://www.cdc.gov/ncidod/diseases/hepatitis/slideset/index.htm. Accessed June 22, 2005.Google Scholar The clinical course and symptoms of acute HBV infection are similar to those of other types of acute viral hepatitis. The incubation period averages 60 to 90 days, with a range of 45 to 180 days. Clinical illness occurs more often in adults than in children; however, approximately 50% of adults are asymptomatic.7Centers for Disease Control and PreventionHepatitis B.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 191-212Google Scholar In adults, most acute HBV infections result in complete recovery, with elimination of HBsAg from the blood and production of antibodies to HBsAg (anti-HBs) providing immunity from future infection. However, fulminant hepatitis results in an acute case–fatality rate of approximately 0.5% to 1.0%.Figure 2Typical clinical and laboratory events in an acute hepatitis B virus (HBV) infection. anti-HBc = antibody to hepatitis B core antigen; anti-HBe = antibody to HBeAg; anti-HBs = antibody to HBsAg; HBeAg = hepatitis B envelope antigen, which can be present only with HBsAg; HBsAg = hepatitis B surface antigen; IgM = immunoglobulin M. (Adapted from Epidemiology and Prevention of Viral Hepatitis A to E.8Centers for Disease Control and Prevention, National Center for Infectious Diseases. Viral hepatitis slide set. Epidemiology and prevention of viral hepatitis A to E: an overview—hepatitis B with notes. Available at: http://www.cdc.gov/ncidod/diseases/hepatitis/slideset/index.htm. Accessed June 22, 2005.Google Scholar)View Large Image Figure ViewerDownload (PPT)Most of the serious complications associated with HBV infection are related to chronic infection (Figure 3).9Torresi J. Locarnini S. Antiviral chemotherapy for the treatment of hepatitis B virus infections.Gastroenterology. 2000; 118: S83-S103Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar, 10Perrillo R.P. Wright T. Rakela J. et al.Lamivudine North American Transplant GroupA multicenter United States-Canadian trial to assess lamivudine monotherapy before and after liver transplantation for chronic hepatitis B.Hepatology. 2001; 33: 424-432Crossref PubMed Scopus (413) Google Scholar, 11Moyer L.A. Mast E.E. Hepatitis B virology, epidemiology, disease, and prevention, and an overview of viral hepatitis.Am J Prev Med. 1994; 10: 45-55PubMed Google Scholar, 12Fattovich G. Giustina G. Schalm S.W. et al.EUROHEP Study Group on Hepatitis B Virus and CirrhosisOccurence of hepatocellular carcinoma and decompensation in Western European patients with cirrhosis type B.Hepatology. 1995; 21: 77-82PubMed Google Scholar Chronic HBV infection is associated with chronic hepatitis, cirrhosis, liver failure, and hepatocellular carcinoma. HBV infection in ≤90% of newborns progresses to chronic disease, whereas <10% of immunocompetent adults become carriers of chronic infection.7Centers for Disease Control and PreventionHepatitis B.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 191-212Google Scholar, 13Lok ASF, McMahon BJ. AASLD practice guidelines: chronic hepatitis B. Hepatology. 2001;34:1225–1241. Available at: http://www.aasld.org/eweb/docs/chronichep_B.pdf. Accessed September 9, 2005.Google Scholar In the United States, an estimated 3,000 to 4,000 persons die of HBV-related cirrhosis and 1,000 to 1,500 persons die of HBV-related liver cancer each year. Although individuals with chronic HBV infection may be asymptomatic and unaware that they are infected, they are capable of infecting others.7Centers for Disease Control and PreventionHepatitis B.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 191-212Google ScholarFigure 3Hepatitis B disease progression. HBV = hepatitis B virus; HCC = hepatocellular carcinoma. (Adapted from Gastroenterology,9Torresi J. Locarnini S. Antiviral chemotherapy for the treatment of hepatitis B virus infections.Gastroenterology. 2000; 118: S83-S103Abstract Full Text Full Text PDF PubMed Scopus (119) Google ScholarHepatology,10Perrillo R.P. Wright T. Rakela J. et al.Lamivudine North American Transplant GroupA multicenter United States-Canadian trial to assess lamivudine monotherapy before and after liver transplantation for chronic hepatitis B.Hepatology. 2001; 33: 424-432Crossref PubMed Scopus (413) Google ScholarAm J Prev Med,11Moyer L.A. Mast E.E. Hepatitis B virology, epidemiology, disease, and prevention, and an overview of viral hepatitis.Am J Prev Med. 1994; 10: 45-55PubMed Google Scholar and Hepatology.12Fattovich G. Giustina G. Schalm S.W. et al.EUROHEP Study Group on Hepatitis B Virus and CirrhosisOccurence of hepatocellular carcinoma and decompensation in Western European patients with cirrhosis type B.Hepatology. 1995; 21: 77-82PubMed Google Scholar)View Large Image Figure ViewerDownload (PPT)Hepatitis B is transmitted by parenteral or mucosal exposure to body fluids from an infected person. A person with either acute or chronic hepatitis B is infectious whenever HBsAg is present in the blood. The 3 modes of transmission of HBV are perinatal, sexual, and parenteral. Sexual contact, either heterosexual or homosexual, is the most common mode of HBV transmission in the United States.7Centers for Disease Control and PreventionHepatitis B.in: Atkinson W. Hamborsky J. Wolfe C. Epidemiology and Prevention of Vaccine-Preventable Diseases. 8th ed. Public Health Foundation, Waldorf, MD2005: 191-212Google ScholarA comprehensive strategy to eliminate HBV transmission—recommended in 1991 by the ACIP14Centers for Disease Control and PreventionHepatitis B virus: a comprehensive strategy for eliminating transmission in the United States through universal childhood vaccination: recommendations of the Immunization Practices Advisory Committee (ACIP).MMWR Recomm Rep. 1991; 40: 1-25Google Scholar—includes prenatal testing of pregnant women, universal vaccination of infants, and vaccination of adults at high risk of infection. In addition, routine hepatitis A vaccination of infants and children is currently recommended in US communities with high rates of HAV.15Centers for Disease Control and PreventionPrevention of hepatitis A through active or passive immunization recommendations of the Advisory Committee on Immunization Practices (ACIP).MMWR Recomm Rep. 1999; 48: 1-37Google Scholar Although these policies have been successful in the pediatric population, the greatest challenge to eliminating HAV and HBV transmission in this country is the vaccination of adults who are at high risk for exposure.This supplement includes contributions from a world-renowned panel of experts who provide state-of-the-art information on vaccine-preventable hepatitis. Organized into 6 sections, the supplement addresses a wide range of topics related to the prevention of hepatitis A and B.In the first section of this supplement, Overview of Vaccine-Preventable Hepatitis, Dr. Jeffrey P. Davis reviews clinical trial experience with hepatitis A and B vaccines in healthy individuals, those with chronic liver disease or human immunodeficiency virus (HIV) infection, and those receiving hemodialysis. Dr. Davis describes the impact that these vaccines and national recommendations for vaccination have had on reducing the incidence of HAV and HBV infections. Age-based recommendations for vaccination of individuals against hepatitis A and B have proven to be highly effective. However, despite significant reductions in the overall incidence of hepatitis A and B that occurred as a result of widespread use of these vaccines, the incidence of infection in certain groups—such as international travelers and men who have sex with men (MSM)—has increased. Dr. Davis suggests that expansion of recommendations to include universal vaccination of adults will provide maximal protection among the general population in the United States and further reduce the burden of viral hepatitis.Next, Dr. Gregory A. Poland reviews current recommendations from the ACIP for use of both hepatitis A and B vaccines and discusses why these risk-based recommendations may miss many candidates who are at risk. Because risk-based recommendations fail to protect up to half of those who become infected with vaccine-preventable hepatitis, suggestions are provided for situations in which additional recommendations may be useful. Dr. Poland proposes that universal vaccination will aid in eliminating hepatitis A and B in the United States by vaccinating those unaware of their risk for infection as well as those who will develop risk factors later in life.In the second section, Gastroenterology and Hepatology, Dr. Emmet B. Keeffe reviews major publications demonstrating that acute hepatitis A and most likely acute, but certainly chronic, hepatitis B superimposed on other causes of chronic liver disease are associated with a more severe clinical course, including a higher mortality rate. Acute hepatitis A superimposed on chronic liver disease is associated with more severe liver disease and a higher fatality rate than is acute hepatitis A alone, and acute hepatitis B superimposed on chronic hepatitis C is associated with more severe liver disease than is acute hepatitis B alone. Chronic coinfection with HBV and hepatitis C virus (HCV) is associated with more severe laboratory abnormalities, worse histologic disease, more complications of cirrhosis, and a higher incidence of hepatocellular carcinoma than is either infection alone. Studies have demonstrated that hepatitis A and B vaccination is safe and effective in patients with mild-to-moderate chronic liver disease but less effective in those with decompensated cirrhosis, such as in patients awaiting liver transplantation. Because patients with all chronic liver diseases appear to be at increased risk of a more severe course if infected with HAV or HBV, and patients receiving liver transplants have a risk of de novo HBV infection, Dr. Keeffe suggests that it is reasonable to vaccinate patients with chronic liver disease against both hepatitis A and B early in the natural history of their liver disease.Drs. Daryl T.-Y. Lau and Alex T. Hewlett then explore the issues surrounding prevaccination screening and postvaccination testing for HAV and HBV in patients with chronic liver disease, including cost-effectiveness, disease prevalence, and the accuracy of the screening tests. These authors suggest that the decision to prescreen for HAV should be based on the local epidemiology and prevalence of hepatitis A in the community as well as on patient factors such as race, socioeconomic status, and age. For hepatitis B vaccination, prescreening is indicated given the high prevalence of prior hepatitis B immunity in patients with chronic liver disease and issues of compliance. Because between approximately 30% to 40% of patients with chronic liver disease demonstrate no response to hepatitis B vaccination, postvaccination testing should be performed to ensure adequate seroprotection.Dr. Maria H. Sjogren describes potential reasons for nonresponse or waning immunity following vaccination against hepatitis B and discusses approaches to successful immunization of the 10% of adults and 5% of infants, children, and adolescents in whom an adequate response in anti-HBs serum levels is not seen following 3 doses of hepatitis B vaccine. Contributing causes for nonresponse to the vaccine are genetic predisposition, immunosuppression, and certain chronic illnesses. When individuals at risk of nonresponse are identified, they should be tested for serum levels of anti-HBs 1 to 6 months after receiving the third vaccine dose to determine their degree of response. Dr. Sjogren proposes that true nonresponders may benefit from additional or higher vaccine doses.Despite the recognized importance of vaccination against hepatitis A and B in patients with chronic liver disease, obstacles can interfere with appropriate and timely hepatitis immunization in this population. Ms. Kathleen Bockhold and colleagues discuss the fact that costs of hepatitis A and B vaccine series are out of reach for many uninsured patients. Many private and government-sponsored insurance programs do not routinely cover these vaccinations for patients with chronic liver disease. In addition, inconsistent recommendations by government and national organizations may lead to uncertainty and inconsistent vaccination practices among healthcare providers. Patient compliance also can be an issue because of the need for multiple office visits for prescreening assessment, vaccine administration, and postvaccination testing. These authors suggest that improved coverage of vaccines by government and third-party health plans, as well as uniform guidelines with regard to vaccination of patients with chronic liver disease, are needed. A combination of interventions can be used to facilitate timely and appropriate vaccination against hepatitis and to improve vaccination coverage in patients with chronic liver disease.In the next section of this supplement, Travel Medicine, Dr. Robert Steffen discusses the changing travel-related global epidemiology of hepatitis A. Although sanitation conditions have improved in many developing countries, hepatitis A is highly endemic in many emerging cultures, and nonimmune international travelers remain at risk for contracting hepatitis A. Travelers who have prolonged stays, live in rural areas, consume water or food prepared under unsanitary conditions, or live in close contact with locals are at greatest risk of HAV infection. However, short-term vacationers or business travelers who stay in deluxe accommodations also can be at risk. Hepatitis A vaccination programs for travelers who are at highest risk have not proven effective. Therefore, Dr. Steffen suggests that universal immunization against hepatitis A should be considered.Among industrialized nations, the United States annually receives the greatest number of immigrants as permanent residents. Dr. Elaine C. Jong discusses the unique regional epidemiology of hepatitis A in the United States and explores the impact of newly arriving immigrants, undocumented workers, and seasonal migrant workers on the epidemiology of HAV infection. Data suggest that the majority of foreign-born persons in this country originated in regions considered highly endemic for hepatitis A, including Mexico, Asia, Latin America, the Philippines, and Africa. Dr. Jong also discusses the impact on HAV transmission by a group of nontraditional travelers, immigrants and migrant workers, returning home to visit friends and relatives in their country of origin.Current recommendations state that travelers should receive hepatitis A vaccine a minimum of 2 to 4 weeks before departure. Dr. Bradley A. Connor reviews the evidence to support hepatitis A vaccination of the imminently departing traveler. Although clinical trials of hepatitis A vaccines measured antibody response at 2 and 4 weeks postvaccination, other studies investigated early seroconversion. These studies found that the majority of vaccinees develop antibodies within 2 weeks of vaccination, some as early as 12 days postvaccination. This is relevant information given that hepatitis A has an average incubation period of 28 days. Dr. Connor discusses data suggesting that clinical disease does not occur at antibody levels lower than those currently accepted as “protective.” In addition, evidence shows that a single dose of vaccine can halt outbreaks if enough susceptible individuals are vaccinated. Information from rapid outbreak control studies and those assessing postexposure administration of hepatitis A vaccine suggest that late vaccination provides a significant degree of protection. On the basis of available evidence, it appears reasonable to administer hepatitis A vaccine to travelers at any time prior to departure because it will still provide travelers with protection.Dr. Jay S. Keystone reviews the evidence for travel as a risk factor for hepatitis B infection. Epidemiologic factors associated with acquisition of HBV include the prevalence of hepatitis B in the local population; the extent of contact with blood and body fluids; the risk of injury, accidents, or need for medical care; the quality of the healthcare system; and the duration of travel. The risk of hepatitis B for long-stay travelers, such as expatriates, is well documented. On the other hand, risk data for short-term travelers are lacking and based primarily on surrogate risks such as medical, surgical, and dental interventions; cosmetic procedures (e.g., tattooing, skin piercing); unprotected sexual contact with a new partner; and close, nonsexual personal contact with the indigenous population in an area of high endemicity for hepatitis B. In addition, Dr. Keystone discusses the use of accelerated schedules for hepatitis B immunization for travelers because international travelers are often “last-minute” travelers, with almost 67% of travelers planning their trip or seeking health advice <4 weeks prior to departure. Although long-term efficacy studies of accelerated schedules for hepatitis B immunization have not been carried out, the results of immunogenicity studies suggest that excellent, rapid, and long-term protection will result.In the fourth section of this supplement, Infectious and Sexually Transmitted Diseases, Dr. H. Hunter Handsfield discusses vaccination against hepatitis A and B in patients being evaluated for sexually transmitted diseases (STDs). Sexual transmission accounts for most HBV infections in industrialized countries. Hepatitis A can be transmitted by sexual practices that foster fecal-oral exposure, and both infections remain disproportionately frequent in MSM. Routine immunization against hepatitis B is recommended for MSM and for persons being evaluated or treated for STDs, and hepatitis A immunization is advised for MSM and for other persons at risk—such as users of illegal drugs—who are commonly seen in STD care settings. Although success has been documented with vaccinating persons at risk in public STD clinics and other settings, at a national level efforts to achieve desired immunization rates have largely failed. Numerous attitudinal and structural barriers interfere with routine immunization in persons at risk for sexual transmission. Dr. Handsfield suggests that until universal childhood immunization produces a largely immune adult population, a strategy of universal vaccination for adults may be more successful than the present risk-based recommendations in reaching persons at risk because of potential sexual exposure.In the second article in this section, Dr. Jeffrey C. Laurence describes the impact of HAV or HBV coinfection in HIV-positive individuals, the importance of vaccinating against hepatitis A and B in these patients, and results of vaccine trials that demonstrate the safety and immunogenicity of hepatitis A and B vaccines in the HIV-positive population. Because immune reactivity to hepatitis B vaccines is frequently suboptimal in patients with HIV in terms of rate of response, antibody titer, and durability, Dr. Laurence provides strategies to ensure adequate hepatitis B vaccine response and protection against HBV infection. The best time to vaccinate against hepatitis A and B is early in the course of caring for an HIV-positive person, and Dr. Laurence suggests that universal, age-based vaccination is the best way to guarantee reaching all high-risk populations.Next, Dr. Elizabeth F. Gondles describes characteristics of the incarcerated population in the United States and explains why this population should routinely be immunized against hepatitis A and B. Many offenders engage in sexual and drug-use behaviors that put them and their contacts at risk for infection with HAV, HBV, or HCV. High rates of HBV and HCV infection in correctional populations can be attributed to inadequate education about viral hepatitis, the tendency of offenders to reject educational efforts, insufficient substance abuse education, and a lack of drug treatment and immunization programs. Dr. Gondles cautions that as individuals pass in and out of the nation’s jails and prisons, so does viral hepatitis. Thus, the prevalence of hepatitis infection among the incarcerated population is a health problem not only for the correctional system but also for the community at large. However, the unique circumstances of the correctional environment create an unmatched opportunity to reach a population at high risk. Dr. Gondles calls for routine immunization against hepatitis A and B for all offenders.In the penultimate section of this supplement, Primary Care, Ms. Diane C. Peterson and Dr. Sheila L. Palevsky describe office-based approaches to implementing hepatitis vaccination and discuss tools available to facilitate this process. Key steps in the integration of adult vaccination into routine medical care include provider education; increasing patient awareness; improving physician–patient communication; and adopting practice management tools to identify patients eligible for vaccination, to document vaccine administration, and to track and recall patients to ensure completion of a vaccination series. In addition, efficient office systems can be used to ensure proper handling and administration of vaccines, and appropriate techniques can maximize reimbursement. These authors provide a wealth of resources about hepatitis for clinics, providers, and patients.Dr. Stanley A. Gall focuses on obstetrics and gynecology. He reviews guidelines from the CDC for the prevention of perinatal HBV infection and emphasizes that pregnancy is not a contraindication for hepatitis B vaccination. Although maternal–fetal transmission of HAV has not been reported, hepatitis A during pregnancy can increase the risk of severe infection, spontaneous abortion, and preterm delivery. Dr. Gall explains that the current CDC recommendations for hepatitis A and B vaccines, which focus on 13 and 23 risk groups, respectively, may be too complex for many clinicians to implement successfully; he suggests universal vaccination.In the final section of this supplement, Public Health, Dr. Jody H. Hershey and colleagues present the public health perspective on vaccine-preventable hepatitis. Despite current ACIP recommendations to vaccinate adults in groups at high risk, vaccine coverage among these groups is modest, and many opportunities to vaccinate are missed. Barriers to immunization include the lack of dedicated federal funding to support hepatitis vaccination in adults, the complexity of screening for risk factors, and the stigma patients may associate with revealing certain risk behaviors. Dr. Hershey describes several state and local public health programs that provide small-scale hepatitis A and B vaccination programs for adults in public health settings serving adults at risk. These programs demonstrate that successful immunization programs for adults at high risk are possible in the settings of STD clinics, HIV counseling and testing sites, drug treatment programs, and correctional facilities. A commitment from the federal government to provide dedicated, sustained funding to support vaccination programs for adults and a policy of universal vaccination are needed to eliminate HAV and HBV infections in the United States.SummaryInfections caused by vaccine-preventable hepatitis create a substantial burden in terms of morbidity, mortality, and cost. Central to all of the articles within this supplement is the underlying theme that hepatitis A and B are preventable diseases, and that risk-based recommendations for vaccinat