Safety and immunogenicity of a yeast-derived recombinant hepatitis B vaccine in Bulgarian newborns

Background: In 1998, Bulgaria adopted a recombinant DNA yeast-derived hepatitis B (HB) vaccine (Euvax B (TM)) for universal vaccination of all Bulgarian newborns on a 0-1-6 month schedule, the first dose to be given within 24 h of birth. Materials and Methods: We evaluated the safety, immunogenicity and effectiveness of this vaccine in over 40,000 healthy infants from July 1998 to December 1999. Standard safety information was collected for all infants vaccinated, subsets being followed for solicited local and systemic adverse events (n = 200) and antibodies to HB surface antigen (anti-HBsAg) 1-3 months after the third dose (n = 140). Results: No serious adverse events were registered for any vaccinee, solicited local reactions were rare (< 1.5%), mild and transient. The overall geometric mean titer (GMT) was 1,012 mIU/ml (95% CI: 786; 1,302), the seroprotection rate being 98.6%. Conclusion: These surveillance data, obtained under the conditions of universal infant immunization show the novel recombinant HB vaccine, Euvax B (TM), is safe and well-tolerated with an immunogenicity similar to other recombinant HB vaccines.