Effect of a Hepatitis B Vaccination Program on the Prevalence of Hepatitis B Virus Infection

In April 1991, surveys for serologic evidence of hepatitis B virus (HBV) infection were conducted among 3- to 4-year-old children born after a hepatitis B immunization program of newborns began and among 6- to ll-year-old children targeted for early childhood vaccination in American Samoa. Compared with 3- to 4-year-olds tested in 1991, children tested at baseline in 1985 were more likely to have been infected with HBV (5/40 vs. 2/93; prevalence ratio [PRJ = 5.8, 95% confidencelimits [CL] = 1.2,28.7) and to have chronic infection with HBV (3/40 vs. 0/95; PR = undefined, lower CL = 1.2). Compared with 6- to ll-year-olds tested in 1991, children in 1985 weremore likelyto have been infectedwith HBV(32/121 vs. 53/386; PR = 1.9, CL = 1.3,2.8) and to have chronic infection with HBV (8/121 vs. 7/386; PR = 3.6, CL = 1.3, 9.8). The incorporation of hepatitis B vaccine into routine childhood vaccination schedules can prevent acute and chronic HBV infection in areas of high endemicity.