EPIDEMIOLOGY AND PREVENTION OF HEPATITIS B VIRUS INFECTIONINFO:

January 21, 2000

EPIDEMIOLOGY AND PREVENTION OF HEPATITIS B VIRUS INFECTION

Infections among Infants and Children

In the United States, children become infected with HBV through a variety of

means. The risk of perinatal HBV infection among infants born to

HBV-infected mothers ranges from 10% to 85%, depending on each mother's

hepatitis B e antigen (HBeAg) status (3,7,8). Infants who become infected by

perinatal transmission have a 90% risk of chronic infection, and up to 25%

will die of chronic liver disease as adults (9). Even when not infected

during the perinatal period, children of HBV-infected mothers remain at high

risk of acquiring chronic HBV infection by person-to-person (horizontal)

transmission during the first 5 years of life (10). More than 90% of these

infections can be prevented if HBsAg-positive mothers are identified so that

their infants can receive hepatitis B vaccine and hepatitis B immune

globulin (HBIG) soon after birth (4,5).

Because screening selected pregnant women for HBsAg has failed to identify a

high proportion of HBV-infected mothers (11,12), prenatal HBsAg testing of

all pregnant women is now recommended (1,13,14). Universal prenatal testing

would identify an estimated 22,000 HBsAg-positive women and could prevent at

least 6,000 chronic HBV infections annually (3). Screening and vaccination

programs for women and infants receiving care in the public sector have

already been initiated through state immunization projects.

Horizontal transmission of HBV during the first 5 years of life occurs

frequently in populations in which HBV infection is endemic. The risk of

chronic infection is age dependent, ranging from 30% to 60% for children 1-5

years of age (15). Worldwide, it has been recommended that, in popula- tions

in which HBV infection is acquired during childhood, hepatitis B vaccine

should be integrated into routine vaccination schedules for infants, usually

as a part of the World Health Organization's Expanded Programme on

Immunization (16). In the United States, racial/ethnic groups shown to have

high rates of childhood HBV infection include Alaskan Natives (6,17),

Pacific Islanders (18), and infants of first-generation immigrant mothers

from parts of the world where HBV infection is endemic, especially Asia

(19,20). Vaccination programs to prevent perinatal, childhood, and adult HBV

infections among Alaskan Natives were begun in late 1982; as a result, the

incidence of acute hepatitis B in this population has declined by over 99%

(6). Hepatitis B vaccine was integrated into vaccination schedules for

infants in American Samoa beginning in 1986 and by 1990 was incorporated

into the schedules of the remaining Pacific Islands under U.S. jurisdiction.

Each year, approximately 150,000 infants are born to women who have

immigrated to the United States from areas of the world where HBV infection

is highly endemic (3). Children born to HBsAg-positive mothers can be

identified through prenatal screening programs. However, children born to

HBsAg-negative immigrant mothers are still at high risk of acquiring HBV

infection, usually from other HBV carriers in their families or communities

(3,19,20). Infections among these children can be prevented by making

hepatitis B vaccine part of their routine infant vaccinations (1).

Infections among Adolescents and Adults

In the United States most persons with hepatitis B acquire the infection as

adolescents or adults. Several specific modes of transmission have been

identified, including sexual contact, especially among homosexual men and

persons with multiple heterosexual partners; parenteral drug use;

occupational exposures; household contact with a person who has an acute

infection or with a chronic carrier; receipt of certain blood products; and

hemodialysis. However, over one-third of patients with acute hepatitis B do

not have readily identifiable risk factors (1,2).

The rates of HBV infection differ significantly among various racial and

ethnic groups (2,21). For example, the prevalence of infection among

adolescents and adults has been shown to be threefold to fourfold greater

for blacks than for whites and to be associated with serologic evidence of

previous infection with syphilis (21,22).

Efforts to vaccinate persons in the major risk groups have had limited

success. For example, programs directed at injecting drug users failed to

motivate them to receive three doses of vaccine (CDC, unpublished data).

Health-care providers are often not aware of groups at high risk of HBV

infection and frequently do not identify candidates for vaccination during

routine health-care visits (CDC, unpublished data). In addition, there has

been limited vaccination of susceptible household and sexual contacts of

HBsAg carriers identified in screening programs for blood donors (23).

Hepatitis B vaccination of health-care workers appears to have resulted in a

substantial decrease in the rate of disease in this group, but has had

little effect on overall rates of hepatitis B (2). Moreover, to achieve

widespread vaccination of persons at occupational risk, regulations have had

to be developed to ensure implementation of vaccination programs (24).

Educational programs to reduce parenteral drug use and unprotected sexual

activity are important components of the strategy to prevent infection with

the human immunodeficiency virus (HIV), which causes acquired

immunodeficiency syndrome. These programs appear to have reduced the risk of

HBV infections among homosexual men but have not had an impact on hepatitis

B attributable to parenteral drug use or heterosexual trans- mission (2).

Educational efforts alone are not likely to fully eliminate the high-risk

behaviors responsible for HBV transmission.

CDC

http://aepo-xdv-www.epo.cdc.gov/wonder/prevguid/m0033405/m0033405.htm

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January 21, 2000