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Background: Hepatitis A (HepA) vaccines are recommended for US adults at risk of HepA. Ongoing United States (US) HepA outbreaks since 2016 have primarily spread person-to-person, especially among at-risk groups. We investigated the health outcomes, economic burden, and outbreak management considerations associated with HepA outbreaks from 2016 onwards., Methods: A systematic literature review was conducted to assess HepA outbreak-associated health outcomes, health care resource utilization (HCRU), and economic burden. A targeted literature review evaluated HepA outbreak management considerations., Results: Across 33 studies reporting on HepA outbreak-associated health outcomes/HCRU, frequently reported HepA-related morbidities included acute liver failure/injury (n = 6 studies of 33 studies) and liver transplantation (n = 5 of 33); reported case fatality rates ranged from 0% to 10.8%. Hospitalization rates reported in studies investigating person-to-person outbreaks ranged from 41.6% to 84.8%. Ten studies reported on outbreak-associated economic burden, with a national study reporting an average cost of over $16 000 per hospitalization. Thirty-four studies reported on outbreak management; challenges included difficulty reaching at-risk groups and vaccination distrust. Successes included targeted interventions and increasing public awareness., Conclusions: This review indicates a considerable clinical and economic burden of ongoing US HepA outbreaks. Targeted prevention strategies and increased public awareness and vaccination coverage are needed to reduce HepA burden and prevent future outbreaks., Competing Interests: Potential conflicts of interest . E.K.H., O.H.R., and A.M.A. are employees of and hold shares in GSK. A.S., B.J., and E.L. are employees of OPEN Health, which was paid by GSK to conduct this study. All authors declare no other financial and non-financial relationships and activities. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© GSK 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: In recent years, the number of travelers aged >40 years who acquire hepatitis A while traveling has increased. Therefore, there is a need to review hepatitis A vaccination protocols in travelers. The aims of the study were to assess immunity levels to hepatitis A virus (HAV) in international travelers >40 years and to determine the least costly immunization strategy., Methods: A serological examination of HAV antibodies in 427 international travelers aged >40 years traveling endemic zones was carried out. The prevalence of antibodies in each age group was assessed. The costs of two preventive strategies, direct vaccination of all subjects (independent of the immune status) or screening and subsequent vaccination of susceptible subjects were compared. The critical value of prevalence (CVP) (the value at which the costs for the two strategies are equal) was calculated., Results: Total prevalence of HAV antibodies was 78.9% [95% confidence interval (CI): 74.8-82.5] and was 80.0% (95% CI: 73.8-85.2) in men and 77.9% (95% CI: 71.9-83.2) in women. There was a positive association with age. In the 40 to 49, 50 to 59, 60 to 69, and 70 to 95 years age groups, the prevalence rates were 62.6 (95% CI: 53.8-71.5), 76.8 (95% CI: 70.0-82.7), 91.7 (95% CI: 85.2-95.6), and 97.5% (95% CI: 87.4-99.6), respectively. The CVP was 58.4% using two doses of vaccine., Conclusions: The CVP was lower than the prevalence rate found in our international travelers. Therefore, we recommend systematic screening for HAV antibodies before selective vaccination of international travelers aged >40 years traveling to hepatitis A endemic zones.

We analyzed the cost-effectiveness of hepatitis A vaccination regimens using a mathematical simulation model. Passive immunization and two active vaccination strategies (with and without prior screening) were compared with "doing nothing." Hepatitis A antibodies were determined in 2,325 Dutch marines; other input data were retrieved from published and unpublished sources. The prevalence of hepatitis A antibody was 14%. Screening before vaccination was identified as appropriate at a prevalence > 20%. Passive immunization was the cheapest prevention for a single 6-month deployment per 10 years. The inactivated vaccine containing 1,440 enzyme-linked immunosorbent assay units without prior screening was identified as the best option for more frequent deployments. It was cost-saving with two or more missions per 10 years. A 5.3% hepatitis A attack rate validated the investment for this policy. Overall, immunization with inactivated hepatitis A vaccine without prior screening proved to be the optimum strategy for troops at regular risk.