On Oct. 4, 1990, the FDA approved the use of Haemophilus b Conjugate Vaccine (Diphtheria CRM 197 Protein Conjugate) (HbOC), manufactured by Praxis Biologics (now Pfizer), for routine administration to infants beginning at 2 months of age. Haemophilus influenzae type b (Hib) is the leading cause of invasive bacterial disease among children in the U.S.