Diphtheria with Haemophilus influenzae, poliomyelitis, pertussis and tetanus should be administered at what age?

• A. At 6 weeks
• B. At 4 weeks
• C. At 2 months
• D. At 12 weeks

Answer: (C)

Starting this pentavalent vaccination at about two months allows the infant to mount a strong immune response once maternal antibodies have waned enough, while still providing protection early in life. Administering the first dose at two months sets up proper priming for diphtheria, tetanus, pertussis, Hib, and polio, with subsequent doses at roughly four and six months to complete the primary series and build lasting immunity. Giving the first dose earlier, such as at six weeks or four weeks, may result in a less robust response in some infants, and delaying until twelve weeks would leave the infant unprotected longer. Thus, two months is the recommended starting age.