Healthy infants were randomized to receive a combination DTPa-HepB vaccine ( diphtheria and tetanus toxoids , acellular pertussis antigens and hepatitis B surface antigen ) , concomitantly with type b and oral poliovirus vaccines at 2 , 4 and 6 months of age ( Group 1 ) or HepB vaccine given at birth , 1 month and 6 months of age and DTPa , type b and oral poliovirus vaccines given at 2 , 4 and 6 months of age ( Group 2 ) .
