Effect of the revision of the recommended vaccination schedule for preventing vertical transmission of hepatitis B virus on vaccination status of infants in Japan.

BACKGROUND: In 1986, a strategy of vaccinating infants at 2, 3, and 5 months of age was implemented in Japan to prevent the vertical transmission of the hepatitis B virus. This strategy was revised in 2013 to vaccinate infants at birth, 1 month, and 6 months of age. We aimed to evaluate the effect of this policy change on the vaccination status of infants born to mothers with positive hepatitis B surface antigen. METHODS: We identified infants born between April 2009 and March 2021 from the JMDC Claims Database. Administration of hepatitis B immunoglobulin at birth was used to identify infants who received preventive measures against vertical transmission. The timing of hepatitis B vaccine administration within 12 months of birth was compared between old (born between April 2009 and September 2013) and new (born between October 2013 and March 2021) groups. RESULTS: Among the 77,797 and 510,584 infants born before and after October 1 2013, respectively, 190 (0.24%) and 732 (0.14%) were analyzed. The proportion of infants receiving at least one dose of the vaccine increased from 63% to 96% (p < 0.001). The proportion of infants who received timely first, second, and third doses of vaccines changed from 54% to 90% (p < 0.001), 46% to 59% (p = 0.002), and 39% to 31% (p = 0.034), respectively. CONCLUSIONS: The change in strategy against the vertical transmission of hepatitis B virus resulted in an increased rate of receiving the first dose of the vaccine and a decreased rate of timely completion of the recommended doses.