Hepatitis A vaccine

Hepatitis A is an infectious disease frequently reported in the United States. An average of 26,000 cases were reported each year during 1980 to 1999; probably 3 times as many occurred. Hepatitis A vaccines provide a powerful new prevention tool. The 2 inactivated hepatitis A vaccines available as pediatric and adult formulations in the United States and in many other countries are safe, immunogenic, and efficacious. A single dose provides excellent short-term protection; the second dose is thought to be important for long-term protection. Because hepatitis A virus (HAV) is excreted in high concentrations in the stool, the principal mode of transmission is person-to-person by the fecal-oral route, most commonly among household and sexual contacts of people with HAV infection. Children can be important in transmission because they frequently have unrecognized or asymptomatic infection. Implementation of recommendations for routine hepatitis A vaccination of children living in areas with consistently elevated hepatitis A rates appears to be resulting in dramatic declines in the overall incidence of the disease. Improved vaccination coverage and continued monitoring of incidence rates are needed to determine the overall long-term impact of this strategy.     

Universal hepatitis A vaccination in the United States: a call for action

Previous hepatitis A recommendations for the United States targeted vaccination of at-risk individuals and children living in states and communities with consistently elevated rates of hepatitis A. Recommendations now call for routine hepatitis A vaccination of all children in the United States beginning at age 1 year (12-23 months). Currently, vaccination coverage rates for hepatitis A remain below rates of other routine childhood vaccines. Achieving a national immunization rate greater than 90% for the recommended 2 doses of hepatitis A vaccine would lessen disease impact throughout society. Routine childhood immunization against hepatitis A can be a highly effective strategy to reduce infection in children and community transmission of the virus, and the elimination of indigenous transmission of hepatitis A is an attainable goal.     

Hepatitis A vaccine

Inactivated hepatitis A vaccines are highly immunogenic and efficacious. Because of their high disease rates and importance as a reservoir of transmission to others, children should be the primary focus of vaccination. A long-term strategy of sustained routine vaccination of children living in areas with consistently elevated hepatitis A rates has been adopted. Ultimately, elimination of HAV transmission will require vaccination of all children in the US. This effort would be facilitated by the availability of vaccine formulations or schedules for use in infants or children in the second year of life, and combination vaccines that include hepatitis A.     

A prevalence study of hepatitis A virus infection in a migrant community: Is hepatitis A vaccine indicated?

BACKGROUND: The Advisory Committee on Immunization Practices recommends routine hepatitis A vaccination of children living in communities with high rates of hepatitis A. Rates among children living in migrant farm worker families are unknown. METHODS: Participants recruited from the 1243 migrant children aged 2 to 18 years in Okeechobee County, Florida, were administered a questionnaire. A blood sample was taken for testing for antibodies to hepatitis A virus (anti-HAV), and hepatitis A vaccine was administered. RESULTS: Of 244 (20%) participating children, 125 (51%) were anti-HAV-positive. Seropositivity increased with age from 34% (2- to 5-year-olds) to 81% (>/=14-year-olds) (P <.0001). In multivariate analysis, age (odds ratio [OR] = 1.2/year; 95% CI = 1.1 to 1.3), having a Mexican-born father (OR = 12.2; 95% CI = 2.2 to 227.9), and age on moving to the United States (OR = 1.3/year; 95% CI = 1.0 to 1.6) were independently associated with anti-HAV positivity. Among US-born children aged 2 to 5 years who had never left the United States, 33% were anti-HAV-positive. CONCLUSIONS: Anti-HAV prevalence among migrant children in Okeechobee County, including the youngest US-born children, is high, indicating ongoing transmission of HAV. Children in this and other US migrant communities may benefit from hepatitis A vaccination.     

Epidemiology of hepatitis B and hepatitis B virus infection in United States children

Before the era of routine hepatitis B vaccination, an estimated 24,000 children acquired hepatitis B virus (HBV) infection each year in the United States. Childhood hepatitis B immunization has led to significant declines in the incidence and prevalence of HBV infection in U.S. children. Because the greatest burden of hepatitis B is caused by complications of hepatocellular carcinoma and cirrhosis in adults who were infected with HBV as children, most of the benefits of vaccination have yet to be realized. Reaching the goal of eliminating HBV transmission to children likely will require increasing vaccination coverage, ensuring timely administration of postexposure immunoprophylaxis to prevent more perinatal infections, and continued evaluation of the impact of immunization recommendations.     

Hepatitis A vaccine recommendations

Since licensure in 1995 of a hepatitis A vaccine, the Centers for Disease Control and Prevention and the American Academy of Pediatrics have been implementing an incremental hepatitis A immunization strategy for children. In 1996, children living in populations with the highest rates of disease were targeted for immunization, and in 1999 the program was expanded to immunization of children 2 years and older living in states and counties with rates of hepatitis A that historically have been higher than the national average. The 1999 program has been successful; the current rate of hepatitis A is the lowest ever reported in the United States. Regional, ethnic, and racial differences in the incidence of hepatitis A have been eliminated. The incidence of hepatitis A in adults in immunizing states has decreased significantly, suggesting a strong herd-immunity effect associated with immunization. In 2005, the US Food and Drug Administration changed the youngest approved age of administration of hepatitis A vaccine from 24 to 12 months of age, which facilitated incorporation of the vaccine into the recommended childhood immunization schedule. As the next step in the implementation of the incremental vaccine immunization strategy, the American Academy of Pediatrics now recommends routine administration of a Food and Drug Administration-licensed hepatitis A vaccine to all children 12 to 23 months of age in all states according to a Centers for Disease Control and Prevention-approved immunization schedule. Available data suggest that hepatitis A vaccine can be coadministered with other childhood vaccines without decreasing immunogenicity. Hepatitis A vaccines have proven to be extremely safe. In prelicensure clinical trials of both Havrix (GlaxoSmithKline, Rixensart, Belgium) and Vaqta (Merck & Co Inc, Whitehouse Station, NJ), adverse events were uncommon and mild when they occurred, with resolution typically in less than 1 day. Hepatitis A vaccine is contraindicated in people with a history of severe allergic reaction to a previous dose of hepatitis A vaccine or to a vaccine component. Because the hepatitis A vaccine is an inactivated product, no special precautions are needed for administration to people who are immunocompromised. No data exist about administration of the hepatitis A vaccine to pregnant women, but because it is not a live vaccine, the risk to mother and fetus should be extremely low to nonexistent.     

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

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

Influenza related hospitalisations in Sydney, New South Wales, Australia.

BACKGROUND: Routine influenza vaccination for children aged 6-23 months has recently been recommended in the United States. Accurate assessment of influenza related burden of illness in children could support similar recommendations in other settings. However, routinely available data underestimate the role of influenza in causing hospitalisation, and indirect estimation methods face difficulties controlling for the concurrent circulation of respiratory syncytial virus (RSV). Recent studies from Hong Kong and the United States have used differing methods to estimate the true burden of influenza related hospitalisation, with disparate results. METHODS: Retrospective population based study of children less than 18 years of age from Sydney, Australia, 1994 to 2001. Using two previously reported methods, estimates of annual hospitalisation rates attributable to influenza were derived by comparison of mean hospitalisation rates for acute respiratory disease during periods of high influenza activity and low RSV activity (defined using virological surveillance data) and periods where both influenza and RSV activity were low. These estimates were compared to rates of hospitalisation where influenza was recorded as the principal discharge diagnosis. RESULTS: Hospitalisation rates attributable to influenza were up to 11 times higher, depending on the age group and method used, compared to rates calculated from principal discharge diagnosis codes. CONCLUSIONS: Although there remains considerable uncertainty in estimating influenza related morbidity by methods using excess hospitalisations, even minimum estimates of disease burden warrant consideration of routine influenza immunisation for all children less than 2 years of age. Such estimates, derived from principal discharge diagnosis codes, are available in most settings.     

Nationwide canadian study of hepatitis a antibody prevalence among children eight to thirteen years old

BACKGROUND: Hepatitis A vaccines provide consistent, long-lasting protection and have been available for almost 10 years in Canada, but their use remains limited. It is difficult to assess their optimal utilization given that our knowledge of hepatitis A epidemiology in Canada is fragmentary. Unlike the United States, no nationwide study of hepatitis A prevalence has ever been done in Canada. Consequently we do not know the incidence of infection in children and what would be the most appropriate age for hepatitis A vaccination. OBJECTIVE: To estimate the proportion of 8- to 13-year-old children who have been infected with hepatitis A virus (HAV) and the risk factors for this infection on a nationwide scale. METHODS: Children were sampled in 10 Canadian provinces, comprising 5 regions, using random digit dialing methodology with regional stratification. Demographic data and information about risk factors for hepatitis A were collected by the telephone interviewers. Oral fluid samples were self-collected and mailed to the laboratory, where they were tested for anti-HAV IgG. RESULTS: Of 6740 contacted families with a child of required age, 1688 (25%) agreed to participate and answered the questionnaire. From these, 1074 oral fluid samples were received, and 1057 could be analyzed. Anti-HAV IgG was detected in 2.7% of subjects, with variation by region from 0.8 to 3.4%. The parents of 54 subjects (5.1%) reported that their child had previously been vaccinated against HAV. Anti-HAV IgG was present in 2.0% of unvaccinated subjects, among whom antibody prevalence was 19.4% in children born in HAV-endemic countries, 6.1% in Native children and 4.2% in travelers to endemic countries. In multivariate analysis of all subjects, the presence of anti-HAV IgG was significantly associated with birth in an endemic country, travel to an endemic country, Native status (American Indian and Inuit population), female gender and vaccination against HAV. In nonvaccinated, non-Native children born in Canada who did not travel to endemic countries, anti-HAV prevalence was 1.1%. CONCLUSIONS: The risk for hepatitis A during childhood is low in Canada. Almost all teenagers (>97%) would be at risk for infection in case of contact with HAV. Changes in immunization policy against hepatitis A should be considered.     

Poliovirus vaccines. Progress toward global poliomyelitis eradication and changing routine immunization recommendations in the United States

Poliomyelitis prevention in the United States has relied virtually exclusively on OPV during the past 30 years. Starting in 1997, a major change in the poliomyelitis vaccination policy occurred, facilitated by substantial progress toward worldwide poliomyelitis eradication. A sequential schedule of IPV followed by OPV became the preferred means to prevent poliomyelitis, although an all-OPV and an all-IPV schedule were considered acceptable alternatives. In 1999, two doses of IPV were recommended to start the primary series, followed by two doses of either poliovirus vaccine. As of January 2000, an all-IPV schedule is currently being implemented in the United States for routine childhood vaccination. Several unusual features are associated with the major public health policy change from an all-OPV to a sequential schedule, including (1) the process of involving a neutral party (i.e., the IOM); (2) the perceived concerns expressed before the change in policy with regard to provider and parent compliance, which could affect the hard-earned gains in raising immunization coverage rates; (3) the ethical issues surrounding the change (e.g., societal versus individual protection) and the influence that a single case of VAPP may have on national policy; (4) the relative lack of importance of cost-effectiveness data; and (5) the weight of progress in the global polio eradication initiative spurring the change in the United States and, increasingly, in other industrialized countries. The IOM assisted in the evaluation of the national poliomyelitis vaccination policy in 1977 and again in 1988. The 1988 review recommended that a sequential IPV-OPV schedule be considered at such time that a combination vaccine becomes available. Also, the IOM raised several important questions. Extensive research to address the questions raised by the IOM had been conducted so that, in 1996, more data were available for the decision-making process. The primary reasons for the change in vaccination policy were (1) the continued occurrence of VAPP in the absence of indigenously acquired wildtype poliovirus-associated paralytic disease, (2) the reduced risk for importation and spread of wild-type poliovirus caused by the progress of the global polio eradication initiative, (3) evidence from vaccine trials that combined IPV-OPV schedules are safe and immunogenic, and (4) maintenance of high levels of population immunity to poliovirus. The global effect of a national change in poliomyelitis vaccination policy was also considered in this policy-making process. Some members of the public health and medical communities raised objections that an increased reliance on IPV in the United States could lead other countries, especially developing countries, to inappropriately abandon OPV and increase reliance on IPV for routine vaccination. Experience from the global smallpox eradication campaign indicated that this scenario was unlikely. The United States ceased vaccinating against smallpox in 1971, 6 years before smallpox was eliminated from the world, without jeopardizing the global smallpox campaign. Subsequently, the effect on the global eradication initiative has been negligible. This article illustrates the potential discrepancy between expressed theoretic concerns about the number of injections and the actual practice once vaccination policy recommendations become the standard of care and that appropriate training and education can overcome these initial concerns. The authors found that compliance with the recommended use of IPV for the first and second doses as part of the sequential schedule was high, independent of socioeconomic status and ethnicity. The need for additional injections did not present a barrier to completion of the recommended childhood immunization schedule. (ABSTRACT TRUNCATED)     

Ensuring preparedness for potential poliomyelitis outbreaks: Recommendations for the US poliovirus vaccine stockpile from the National Vaccine Advisory Committee (NVAC) and the Advisory Committee on Immunization Practices (ACIP)

Paralytic poliomyelitis was once endemic in the United States; however, because of high vaccination levels, the last case of wild disease occurred in 1979. Although worldwide polio eradication may be achieved in the near future, the presence of undervaccinated children in urban areas and among groups who refuse vaccination creates an outbreak risk, should importation of wild virus occur. In 1999, the Advisory Committee on Immunization Practices (ACIP) recommended that inactivated poliovirus vaccine (IPV) be used for routine immunization of the US population and that oral poliovirus vaccine (OPV) be reserved for "mass vaccination campaigns to control outbreaks of paralytic polio." Subsequently, the sole US manufacturer of OPV withdrew from the market. In 2003, a joint National Vaccine Advisory Committee (NVAC)/ACIP working group was charged with reporting to its parent bodies concerning the need for a poliovirus vaccine stockpile. Based on that working group's report, the NVAC and ACIP have concluded that stockpiles of both IPV and OPV should be maintained. In the event of an outbreak in which OPV continues not to be available, IPV should be used for control, and a stockpile of 8 million doses seems to be sufficient. Should IPV be manufactured only in combination with other vaccines, appropriate procurement actions should be taken to ensure that uncombined IPV continues to be stockpiled. Under circumstances of diminished population immunity, OPV may offer outbreak control advantages. The NVAC and ACIP recommend that the United States collaborate with international agencies to provide guaranteed and rapid access to at least 8 million doses of trivalent OPV or 8 million doses of each of the 3 types of monovalent OPV. The regulatory and practical obstacles to implementation of this recommendation will require assertive facilitation at high levels of the federal government and careful planning at the state and local levels.     

Regional variation in the cost effectiveness of childhood hepatitis A immunization

BACKGROUND: Routine childhood hepatitis A immunization is recommended in regions with incidence rates twice the national average, but it may be cost-effective in a wider geographic area. OBJECTIVE: To evaluate the costs and benefits of potential hepatitis A immunization of healthy US children in regions with varying hepatitis A incidences. METHODS: We considered vaccination of the 2000 US birth cohort in states defined by historic hepatitis A incidence rates. Infections among potential vaccinees and their personal contacts were predicted from age 2 through 85 years. Net vaccination costs were estimated from health system and societal perspectives and were compared with life-years saved and quality-adjusted life years (QALYs) gained using a 3% discount rate.RESULTS Nationally vaccination would prevent >75 000 cases of overt hepatitis A disease. Approximately two-thirds of health benefits would accrue to personal contacts rather than to vaccinees themselves. In states with incidence rates of > or =200%, 100 to 199%, 50 to 99% and <50% the national average, societal costs per QALY gained would be <0, <0, 13,800 and 63,000 US dollars, respectively. Nationally vaccination would cost 9100 US dollars per QALY gained from the perspective of the health system and 1400 US dollars per QALY gained from society's perspective. Results are most sensitive to vaccination costs and rates of disease transmission through personal contact. CONCLUSION: Childhood hepatitis A vaccination is most cost-effective in areas with the highest incidence rates but would also meet accepted standards of economic efficiency in most of the US. A national immunization policy would prevent substantial morbidity and mortality, with cost effectiveness similar to that of other childhood immunizations.     

Comparison of accelerated and rapid schedules for monovalent hepatitis B and combined hepatitis A/B vaccines in children with cancer

The aim of this study was to determine the efficacy of immunization against hepatitis A and B infections with "rapid" or "accelerated" schedules in children with cancer receiving chemotherapy. Fifty-one children were recruited to receive either vaccination schedule, in the "rapid vaccination schedule"; hepatitis B (group I) or combined hepatitis A/B vaccines (group III) were administered at months 0, 1, 2, and 12; in the "accelerated vaccination schedule," hepatitis B (group II) or combined hepatitis A/B (group IV) vaccines were administered on days 0, 7, 21, and 365 intramuscularly. The seroconversion rates at months 1 and 3 were 35.7 and 57.1% in group I and 25 and 18.8% in group II, respectively. Group I developed higher seroconversion rates at month 3. In group III the seroconversion rates for hepatitis B at months 1 and 3 were 54.5 and 60% and in group IV 50 and 70%, respectively. For hepatitis A, the seroconversion rates at months 1 and 3 were 81.8 and 90% in group III and 80 and 88.9% in group IV, respectively. The accelerated vaccination schedule seems to have no advantage in children receiving cancer chemotherapy except for high antibody levels at month 1. In conclusion, the accelerated vaccination schedules are not good choices for cancer patients. The combined hepatitis A/B vaccine is more effective than monovalent vaccine in cancer patients, which probably can be explained by an adjuvant effect of the antigens. The seroconversion of hepatitis A by the combined hepatitis A/B vaccination is very good in cancer patients.     

Varicella zoster virus infections in children after the introduction of live attenuated varicella vaccine

PURPOSE OF REVIEW: Varicella zoster virus is the cause of both varicella (chickenpox) and herpes zoster (shingles). A live attenuated varicella vaccine was developed in 1974 and was approved in 1995 by the United States Food and Drug Administration for administration to both healthy children (>12 months of age) and adults who are susceptible to varicella. Many studies have shown varicella vaccine to be highly effective. Widespread use of the varicella vaccine in the United States has led to important changes in the epidemiology of the infection. The purpose of this review is to summarize the most recent and important findings regarding the impact that the widespread use of varicella vaccine has had on the epidemiology of varicella zoster infections in children. RECENT FINDINGS: Data from the United States Centers for Disease Control and Prevention have shown a dramatic decline in the incidence of varicella (76 to 87% from 1995 to 2000), with the greatest decline observed in preschool children, as well as a reduction in the number of hospitalizations for cases of varicella. However, as the proportion of children in the United States who have received the varicella vaccine has increased there have been several recent reports in which the effectiveness of the vaccine was substantially lower than expected. In particular, reports during outbreaks of varicella in children have noted increases in breakthrough disease in children who were vaccinated before the age of 15 months, in children with asthma, in those who received the varicella vaccine soon after the measles, mumps, and rubella vaccine (<28 days), and in children who received the vaccine more than 3 years before the development of disease. SUMMARY: Although reports of outbreaks of chickenpox in highly immunized groups have raised questions regarding the need for changes to the current vaccination policy, data undeniably indicate that immunization with varicella vaccine has been and continues to be successful in reducing the burden of disease in children and that universal immunization should continue to be a priority in the United States     

Hepatitis A seroprevalence among infants aged 12 months in Ankara

Seroprevalence studies in various age groups contribute to a better understanding of hepatitis A infection and response to hepatitis A immunization. Hepatitis A seroprevalence in 12-month-old infants from Ankara was studied. Among 601 healthy infants, overall hepatitis A seropositivity was found to be 23.5%. There were no gender differences in seropositivity (22.6% for male and 24.5% for female infants). Although vaccination of infants would be an ideal prevention strategy, presence of maternal anti-hepatitis A virus (HAV) antibody interferes with the immune response to hepatitis A vaccine in infants and young children. Therefore, further knowledge about decay of maternal antibody in infants is important in determining the optimal age for vaccination against hepatitis A. There is no recommendation for routine hepatitis A vaccination in Turkey. However, we need more seroprevalence studies in different age groups to decide the appropriate timing/age of vaccination.     

Measles vaccine

Administration of measles vaccine has sharply reduced the occurrence of measles. However, "mini epidemics" occurring at increasing intervals through 1989 brought about the need for a routine two-dose schedule of measles vaccination. The prevention of preschool cases and school-based cases are two major goals of this new schedule. A two-dose schedule will address the latter goal, however, it will not affect the more difficult problem of measles among preschoolers, a group with lower immunization rates than school-age children. The use of Edmonston-Zagreb measles vaccine in developing countries offers the promise of reducing worldwide disease rates in young infants in the future. However, the major goal in the United States and other developed countries is to increase levels of measles immunity.     

Bacterial meningitis in children

Microbiologic causes of meningitis include bacteria, viruses, fungi, and parasites. Before routine use of pneumococcal conjugate vaccine, bacterial meningitis affected almost 6000 people every year in the United States, and about half of all cases occurred in children 18 years old or younger. Prompt and accurate diagnosis and adequate treatment of bacterial meningitis in children remains a major challenge, as reflected by the continued high morbidity and case-fatality rates of the disease worldwide. Appropriate use of antibiotics, along with adjunctive therapies, such dexamethasone, has proved helpful in the prevention of neurologic sequelae in children with bacterial meningitis. Better understanding of pathophysiologic mechanisms likely would result in more effective therapies in the future.     

Neonatal meningococcal disease in the United States, 1990 to 1999

BACKGROUND: Although neonatal bacterial meningitis is common, the rate of invasive meningococcal disease in the United States among children < or =30 days old has not been defined. Most relevant literature consists of case reports or case series, which note high case-fatality ratios but do not describe the overall burden of disease. METHODS: We used active, population-based surveillance data from the Active Bacterial Core Surveillance program to estimate the incidence of neonatal meningococcal disease in the United States from 1990 to 1999. A case of neonatal meningococcal disease was defined as isolation of Neisseria meningitidis from a normally sterile site in a resident of the surveillance area < or =30 days of age. RESULTS: The median annual number of neonates under surveillance was 25 900. Between 1990 and 1999, 22 cases of neonatal meningococcal disease were identified. Three (14%) patients died. The average annual incidence was 9 per 100 000. CONCLUSIONS: The rate of neonatal meningococcal disease in the United States is higher than previous estimates. Meningococcal disease is uncommon in neonates, but its rate is similar to that of meningococcal disease in 6- to 23-month-old children.     

Evaluation of vaccine coverage in children from 2 to 4 years old in South-Eastern France]

BACKGROUND: Few studies have evaluated vaccination coverage in early childhood in South-Eastern France and spatial and social factors associated to it. POPULATION AND METHODS: We carried out a study in children aged 3.5-4.5 years and attending 112 nursery schools randomly selected in South-Eastern France. Data were collected in 2002-2003 during a mandatory health assessment by physicians and nurses of the services of maternal and infant protection, who completed a new questionnaire developed to standardise these examinations in the whole region. RESULTS: Among the 2959 selected children, 2460 (83.1%) could be included in the study; out of them, 96.4% had been vaccinated against diphtheria and tetanus, 95.0% against poliomyelitis, 92.8% against pertussis, 89.3% against haemophilus influenzae type b and 96.5% against tuberculosis. Vaccination rates at the age of 18 months including the first booster were less important than vaccination rates for children aged 3.5-4.5 years. Only 24.3% of the children had been vaccinated against hepatitis B and 86.4% against measles-mumps-rubella. Vaccination rates at the age of 2, were significantly higher on the basis of the health certificates of the 24th month (CS24) than on the basis of our study. Vaccination rates were highest in urban areas and those with educational priority. CONCLUSION: Vaccination rates at the age of 3.5-4.5 years are satisfying but rates for the first booster should be improved. Vaccination rates against hepatitis B were low when those against MMR do not reach the WHO recommended level of 95.0%. Our results suggest that the analysis of data from the CS24 overestimates the real vaccination coverage at this age in South-Eastern France.     

The cost-effectiveness of adolescent hepatitis A vaccination in states with the highest disease rates

BACKGROUND: The Advisory Committee on Immunization Practices has recommended routine childhood hepatitis A vaccination in states and communities where the incidence of disease exceeds the national average, but most adolescents are currently unprotected from infection. OBJECTIVE: To estimate clinical and economic consequences of vaccinating adolescents against hepatitis A in the 10 states with the highest disease rates. DESIGN: Decision analysis was used to assess cost-effectiveness from societal and health system perspectives. Parameter estimates were obtained from national surveillance data, a study of hepatitis A cases, and an expert panel. MAIN OUTCOME MEASURES: Reduction in disease incidence; costs of vaccination, treatment, and work loss; years of life saved (YOLS); and costs per YOLS. RESULTS: In states with the highest disease rates, vaccination of adolescents against hepatitis A would reduce the lifetime risk of symptomatic infection from 3.3% to 0.7% and prevent loss of 2117 years of life. Vaccination of a single birth cohort would cost $30.9 million, yet treatment and work loss costs would decline $14.2 million and $23.8 million, respectively. Hepatitis A vaccination would cost the health system $7902 per YOLS or $13,722 per discounted YOLS. Results are most sensitive to variation in the discount rate and assumptions regarding long-term vaccine protective efficacy. CONCLUSIONS: Hepatitis A vaccination of adolescents in states with high disease rates would reduce costs to society. Although health system costs would increase, cost-effectiveness is comparable to other recommended vaccines and superior to many commonly used medical interventions. Arch Pediatr Adolesc Med. 2000;154:763-770