Immunizations begin before natural immunity wears off.

Two boosters are given, typically at 1 month and 6 months. This vaccine is especially important for infants who spend time in day-care centers or if the mother is hepatitis B positive, in which case the newborn is given both hepatitis B immune globulin and hepatitis B vaccine.

Hib vaccine prevents Haemophilus influenzae, type B infections, which can cause meningitis, periorbital cellulitis, pneumonia, and epiglottitis. The number of Hib meningitis cases have dropped dramatically since the vaccine was introduced. A meningococcal meningitis vaccine is also available for use in high school and college students.

A high fever, continual crying, or limp, listless behavior are signs of severe reaction that warrant a call to the doctor.

A mild illness, such as a cold with or without fever, shouldn't prevent immunization.

Today, the pertussis vaccine is acellular (the whole bacteria cell is not present) and is denoted as DTaP, a much safer form with minimal side effects.