5. Haemophilus influenzae type b (Hib) conjugate vaccine. (Minimum age: 6 weeks) Routine vaccination:  Administer a Hib vaccine primary series and a booster dose to all infants. The primary series doses should be administered at 2, 4, and 6 months  of age; however, if PRP-OMP (PedvaxHib or Comvax) is administered at  2 and 4 months of age, a dose at age 6 months is not indicated. One  booster dose should be administered at age 12 through15 months.  Hiberix (PRP-T) should only be used for the booster (final) dose in  children aged 12 months through 4 years, who have received at least 1  dose of Hib. Catch-up vaccination:  If dose 1 was administered at ages 12-14 months, administer booster (as final dose) at least 8 weeks after dose 1.  If the first 2 doses were PRP-OMP (PedvaxHIB or Comvax), and were  administered at age 11 months or younger, the third (and final) dose should be administered at age 12 through 15 months and at least 8  weeks after the second dose.  If the first dose was administered at age 7 through 11 months, administer the second dose at least 4 weeks later and a final dose at age 12 through  15 months, regardless of Hib vaccine (PRP-T or PRP-OMP) used for first  dose.  For unvaccinated children aged 15 months or older, administer only 1  dose.  For other catch-up issues, see Figure 2. Vaccination of persons with high-risk conditions:  Hib vaccine is not routinely recommended for patients older than 5 years of age. However one dose of Hib vaccine should be administered to  unvaccinated or partially vaccinated persons aged 5 years or older who  have leukemia, malignant neoplasms, anatomic or functional asplenia  (including sickle cell disease), human immunodeficiency virus (HIV)  infection, or other immunocompromising conditions.