Prevention of Hepatitis A Through Active or Passive Immunization

Groups at Increased Risk for Hepatitis A

The following groups are at increased risk for hepatitis A:

Travelers

Persons from developed countries who travel to developing countries are at substantial risk for acquiring hepatitis A ⁽³⁹⁾. Such persons include tourists, military personnel, missionaries, and others who work or study abroad in countries that have high or intermediate endemicity of hepatitis A (Figure 3). Data from prospective studies indicate that the risk among travelers who do not receive IG is 3/1,000-5/1,000 per month of stay; among some travelers, the risk is higher ⁽⁴⁰⁾. The risk varies according to region visited and the length of stay. The risk for hepatitis A is increased even among travelers who report that they observe measures to protect themselves against enteric infection or stay only in urban areas or luxury hotels, or both (CDC, unpublished data).

Men Who Have Sex with Men

Hepatitis A outbreaks among men who have sex with men have been reported frequently. Recent outbreaks have occurred in urban areas in the United States, Canada, and Australia ⁽²³⁾. Data from prospective serosurveys have demonstrated rates of HAV infection among men who have sex with men that are several-fold higher than those among control populations ^(41,42).

Injecting-Drug Users

During the past decade, outbreaks have been reported among injecting-drug users in the United States and in Europe ^(22,37,38). In the late 1980s, 10%-19% of persons who had hepatitis A reported a history of injecting-drug use; however, in recent years, <3% of infected persons have reported this behavior ⁽²¹⁾.

Persons Working with Nonhuman Primates

Outbreaks of hepatitis A have been reported among persons working with non-human primates that are susceptible to HAV infection, including several Old World and New World species ^(43,44). Primates that were infected were those that had been born in the wild, not those that had been born and raised in captivity.

Risk for Hepatitis A Among Other Groups and Settings

Persons Who Have Chronic Liver Disease. Although not at increased risk for HAV infection, persons who have chronic liver disease are at increased risk for fulminant hepatitis A ⁽⁴⁵⁾. Data from death certificates indicate a high prevalence of chronic liver disease among persons who had fulminant hepatitis A ⁽⁴⁶⁾.

Persons Who Have Clotting-Factor Disorders. During 1992-1993, several outbreaks of hepatitis A were reported in Europe among persons who had clotting-factor disorders who had been administered solvent-detergent-treated factor VIII concentrates that presumably had been contaminated from plasma donors incubating hepatitis A ⁽⁴⁷⁾. In the United States, data from one serologic study suggested that hemophilic patients may be at increased risk for HAV infection ⁽⁴⁸⁾. During 1995-1996, several patients who had clotting-factor disorders reportedly developed hepatitis A after having been administered solvent-detergent-treated factor VIII and factor IX concentrates ⁽⁴⁹⁾.

Food-Service Establishments/Food Handlers. Foodborne hepatitis A outbreaks are relatively uncommon in the United States; however, when they occur, intensive public health efforts are required for their control. These outbreaks are usually associated with contamination of food during preparation by an HAV-infected food handler ⁽⁵⁰⁾, although food (e.g., shellfish) that has been contaminated before reaching the food-service establishment has been associated with some outbreaks ^(51-53). Although persons who work as food handlers have a critical role in common-source foodborne HAV transmission, they are not at increased risk for hepatitis A because of their occupation. In a study of hepatitis A cases in Washington State during 1987-1988, rates of hepatitis A among food handlers were found to be similar to rates among the general population in the state (Trueman Sharp, University of Washington, unpublished data).

Day Care Centers. Outbreaks among children attending day care centers and persons employed at these centers have been recognized since the 1970s ⁽⁵⁴⁾. Because infection among children is usually mild or asymptomatic, outbreaks often are recognized only when adult contacts (usually parents) become ill ⁽⁶⁾. Poor hygiene among children who wear diapers and the handling and changing of diapers by staff contribute to the spread of HAV infection; outbreaks rarely occur in day care centers in which care is provided only to children who do not wear diapers.

Despite the occurrence of outbreaks when HAV is introduced into day care centers, the results of serologic surveys do not indicate a substantially increased prevalence of HAV infection among staff at day care centers compared with the prevalence among control populations ^(55,56). Furthermore, the NHANES-III study did not indicate an increased prevalence of HAV infection among children and adolescents who previously attended day care centers (CDC, unpublished data). Although outbreaks at day care centers occasionally are the sources of outbreaks of hepatitis A within a community, disease within day care centers more commonly reflects extended transmission in the community.

Health-Care Institutions. Nosocomial HAV transmission is rare. Outbreaks have occasionally been observed in neonatal intensive-care units because of infants acquiring infection from transfused blood and subsequently transmitting hepatitis A to other infants and staff ^(11,57,58). Outbreaks of hepatitis A caused by transmission from adult patients to health-care workers are usually associated with fecal incontinence, although most hospitalized patients who have hepatitis A are admitted after onset of jaundice when they are beyond the point of peak infectivity ⁽⁵⁹⁾. Data from serologic surveys of many types of health-care workers have not indicated an increased prevalence of HAV infection in these groups compared with that in control populations ^(60-62).

Institutions for Persons Who Have Developmental Disabilities. Historically, HAV infection was highly endemic in institutions for persons who have developmental disabilities ⁽⁶³⁾. As fewer children have been institutionalized and conditions within institutions have improved, the incidence and prevalence of HAV infection have decreased, although sporadic outbreaks can occur in these settings ⁽⁵¹⁾.

Schools. In the United States, the occurrence of cases of hepatitis A within elementary or secondary schools usually reflects disease acquisition within the community. Child-to-child disease transmission within the school setting is uncommon; thus, if multiple cases occur among children at a school, the possibility of a common source of infection should be investigated ⁽⁵¹⁾.

Workers Exposed to Sewage. Data from serologic studies among Scandinavian and English workers who had been exposed to sewage indicate a possible elevated risk for HAV infection; however, in these studies, the data were not controlled for other risk factors (e.g., socioeconomic status) ^(64,65). In the United States, no work-related cases of HAV transmission have been reported among workers exposed to sewage, and serologic data are not available.

Other Settings. Waterborne outbreaks of hepatitis A are infrequent. Most outbreaks are associated with sewage-contaminated water or inadequately treated water ^(66,67).

Surveillance for Hepatitis A. Hepatitis A is a reportable disease in all states. The goals of hepatitis A surveillance at the national, state, and local levels include a) monitoring disease incidence by identifying acute, symptomatic infections in all age groups; b) determining the epidemiologic characteristics of infected persons, including the source of infection; c) identifying contacts of case-patients who might require postexposure prophylaxis; d) detecting outbreaks; e) determining the effectiveness of hepatitis A vaccination; and f) determining missed opportunities for vaccination.

Cases of hepatitis A should be reported to local or state health departments (according to specific state requirements) so that appropriate control measures can be implemented, if indicated. Cases meeting specified criteria are reported by state health departments to CDC ⁽⁶⁸⁾. Hepatitis A surveillance must be maintained at the local level so that the various immunization strategies recommended in this report can be implemented and their outcome at the local, state, and national levels can be assessed.