Travelers to North America (except Mexico and Central America), western Europe, Japan, Australia, or New Zealand are at no greater risk for infection than in the United States. Data are not available regarding the risk for hepatitis A for persons traveling to developed areas of the Caribbean, although vaccine or IG should be considered if travel to areas that have questionable sanitation is anticipated.

Travelers who are administered vaccine should receive the first vaccine dose at least 4 weeks before travel. Persons can be assumed to be protected by 4 weeks after receiving the first vaccine dose, although a second dose 6-12 months later is necessary for long-term protection. Because protection may not be complete until 4 weeks after vaccination, persons traveling to a high-risk area <4 weeks after the initial dose also should be administered IG (0.02 mL/kg), but at a different anatomic injection site.

Travelers who are allergic to a vaccine component or who elect not to receive vaccine should receive a single dose of IG (0.02 mL/kg), which provides effective protection against hepatitis A for up to 3 months. Travelers whose travel period exceeds 2 months should be administered IG at 0.06 mL/kg; administration must be repeated if the travel period exceeds 5 months.

•Children in communities that have high rates of hepatitis A and periodic hepatitis A outbreaks. Children living in communities that have high rates of hepatitis A should be routinely vaccinated beginning at > 2 years of age. In addition to effectively preventing epidemics of hepatitis A in these communities, vaccination of previously unvaccinated older children is recommended within five years of initiation of routine childhood vaccination programs. Although rates differ among areas, available data indicate that a reasonable cutoff age in many areas is 10-15 years of age because older persons often are already immune and vaccination of younger children will indirectly protect older persons who may be susceptible. Vaccination of children before they enter school should receive highest priority, followed by vaccination of older children who have not been vaccinated. Prevaccination serologic testing is not indicated for vaccination of previously unvaccinated children in this setting.

•Men who have sex with men. Sexually active men who have sex with men (both adolescents and adults) should be vaccinated. Prevaccination testing is not indicated for the vaccination of adolescents in this group, yet may be warranted for adults, especially those >40 years of age, who practice such behaviors.

•Illegal-drug users. Vaccination is recommended for injecting and noninjecting illegal-drug users if local epidemiologic and surveillance data indicate current or past outbreaks among persons with such risk behaviors. Prevaccination testing is not indicated for the vaccination of adolescent illegal-drug users but may be warranted for adults, especially those >40 years of age, who practice such behaviors.

•Persons who have occupational risk for infection. Persons who work with HAV-infected primates or with HAV in a research laboratory setting should be vaccinated. No other groups have been shown to be at increased risk for HAV infection because of occupational exposure.

•Persons who have chronic liver disease. Susceptible persons who have chronic liver disease should be vaccinated. Persons who are either awaiting or have received liver transplants also should be vaccinated.

•Persons who have clotting-factor disorders. Susceptible persons who are administered clotting-factor concentrates, especially solvent-detergent-treated preparations, should be administered hepatitis A vaccine.

•Other groups. Persons who work as food handlers can contract hepatitis A and potentially transmit HAV to others. To decrease the frequency of evaluations of food handlers with hepatitis A and the need for postexposure prophylaxis of patrons, consideration may be given to vaccination of employees who work in areas where state and local health authorities or private employers determine that such vaccination is cost effective.

•Outbreaks in communities that have high rates of hepatitis A. Routine vaccination of children 2 years of age and accelerated vaccination of older children who have not been previously vaccinated should be implemented to control an ongoing outbreak. The upper age for vaccination of older, previously unvaccinated children should be determined by using age-specific rates of hepatitis A (or seroprevalence data, if available). In communities that have begun a vaccination program (i.e., routine vaccination of children 2 years of age and vaccination of older children who have not been previously vaccinated), the vaccination component directed toward older children who have not been previously vaccinated should be accelerated so that at least 70% coverage is achieved as quickly as possible.

•Outbreaks in communities that have intermediate rates of hepatitis A. Hepatitis A vaccination of children or adolescents may have the potential to control hepatitis A outbreaks in these communities. These communities often are located in large cities or counties; thus, widespread vaccination may not be feasible. Targeting vaccination to subpopulations or groups that have the highest rates of disease may be more feasible; however, the effectiveness of using vaccine in these settings and under these conditions has not been determined.

To determine candidate groups for vaccination, local surveillance and epidemiologic data should be used to define populations (e.g., age groups or risk groups) or areas within the community (e.g., census tracts) that have the highest rates of disease. Factors to consider in deciding whether to vaccinate persons in a certain group include a) the feasibility of rapidly vaccinating the target populations of children, adolescents, or young adults; b) program cost; and c) the ability to sustain ongoing vaccination of young children to maintain high levels of immunity and prevent future epidemics.

In some communities, day care centers play a role in sustaining communitywide outbreaks. In this situation, consideration should be given to adding hepatitis A vaccine to the immunoprophylaxis regimen for children and staff in the involved center or centers and, possibly, vaccinating children in day care centers where cases of hepatitis A have not been detected.

Because experience when using hepatitis A vaccine to control hepatitis A in communities that have intermediate rates of hepatitis A is limited, evaluation of the effectiveness of vaccination should be an essential element of programs in these settings.

The Epidemiology Newsletter is published monthly by the Utah Department of Health, Division of Epidemiology and Laboratory Services, Bureau of Epidemiology, to disseminate epidemiologic information to the health care professional and the general public.