Hepatitis B vaccination of newborn infants: clinical study of new vaccine formulation and dose regimen.

To investigate the efficacy in anti-HBsAg response with half the recommended adult dose in a standard vaccination schedule or with a full dose in reduced number of vaccination schedule, 201 healthy newborn infants were randomized to receive either 2.5 micrograms Hevac B vaccine at birth [1, 2 and 14 months in Group I (101)] or 5 micrograms at birth [2 and 14 months in Group II (100)]. Anti-HBsAg responses in the two groups were compared. Passively acquired anti-HBsAg positivity rates at birth were 51.5 and 45.0% in Groups I and II, respectively. Cumulative anti-HBsAg seroconversion rates in Group I were 12.2, 76.6, 82.6 and 86.4% at 2, 4, 14 and 16 months, while the rates in Group II were 2.5, 62.5, 73.7 and 91.0%, showing no significant difference (p greater than 0.05). Significant difference in seroconversion rates at the 2-month follow-up stage between passively acquired anti-HBsAg-negative and -positive groups was observed (11.9 vs. 2.6%). Significant rise in anti-HBsAg titer at 16 months following the booster at 14 months was noted: 36.4 mIU per ml before, 546.4 mIU per ml after in Group I and 25.3 mIU per ml before, 782.6 mIU per ml after in Group II. The booster, 12 months after the primary vaccination series, is therefore considered imperative for maximum effectiveness of hepatitis B active immunization.(ABSTRACT TRUNCATED AT 250 WORDS)