Which vaccine series is administered at 2, 4, and 6 months?

• A. Diphtheria, tetanus, and acellular pertussis (DTaP).
• B. Haemophilus influenzae type B conjugate vaccine (Hib).
• C. Inactivated poliovirus vaccine (IPV).
• D. Meningococcal conjugate vaccine (MenACWY).

Answer: (A)

Infants receive several vaccines as part of an early primary series to build protection during the first months of life. The DTaP vaccine is routinely started at two months and given again at four and six months to complete the three-dose primary series. This schedule targets protection against diphtheria, tetanus, and pertussis during a period when pertussis can be especially dangerous and the immune system is still developing, making a series of doses in quick succession important for strong, early immunity.

Other vaccines also begin in the first year, but the combination of doses at exactly two, four, and six months is classically described for DTaP, while meningococcal vaccines are not started in infancy.