Immunization of newborns of HBsag- positive mothers: A successful first step in control of hepatitis B virus in Taiwan

Abstract

To combat hepatitis B virus (HBV) infection in Taiwan, a mass immunoprophylaxis program was launched on July 1, 1984, aiming first at prevention of chronic HBV carriage from perinatal mother-to-infant infection. In the first 15-month period, 352721 (78%) of 450585 pregnant women were screened for hepatitis B surface antigen (HBsAg); HBsAg was present in 62359 (18%), with 50% of them categorized as highly infectious. Infants born to HBsAg-positive women were given 5 μg of a plasma-derived hepatitis B vaccine at ages 1, 5, and 9 weeks, with a booster at age 12 months. Infants of highly infectious carrier mothers recived an additional 0.5 mL of hepatitis B immune globulin within 24 hours after birth. The coverage rate of the hepatitis B immune globulin was 77% in 27375 infants born to highly infectious mothers, and that of the first, second, third, and the fourth doses of vaccine was 88%, 86%, 84%, and 71%, respectively, in infants of 55620 carrier mothers. The reported untoward reactions to immunization were negligible. We conclude that a mass hepatitis B vaccination program is feasible in hyperendemic areas such as Taiwan; this should be a significant step toward the effective control of HBV infection in these areas. To evaluate the efficacy of the mass hepatitis B vaccination program in Taiwan in interrupting perinatal hepatitis B virus transmission, 3464 randomly selected 18-month-old infant vaccinees born to hepatitis B surface antigen-carrier mothers were recruited from 9697 eligible infants during a six-month period of the program. They were divided into ten groups according to maternal in-fectivity and compliance with the vaccination schedule. Serum samples were tested for hepatitis B surface antigen, antibody to hepatitis B surface antigen, and antibody to hepatitis B core antigen. In 786 infants who had highly infectious mothers and who received hepatitis B immune globulin and vaccine on schedule, the protective efficacy was about 85%. The efficacy seemed to be slightly lower in those immunized off schedule. Overall, 11% of infants still carried hepatitis B surface antigen, and 81% of the infants had antibody to hepatitis B surface antigen that exceeded 10 mlU/ mL in more than 90% of them. The geometric mean titers of antibody to hepatitis B surface antigen were more than 200 mlU/mL in every group of infants. We conclude that the mass vaccination program is efficacious in preventing perinatal hepatitis B virus transmission and the chronic carrier state; most infant vaccinees have adequate levels of protective antibody at 18 months of age. This program is extremely significant in the control of hepatitis B virus infection in Taiwan.