On Jan. 22, 1988, the Immunization Practices Advisory Committee (ACIP) recommended the Hib conjugate vaccine be provided to all children at 18 months of age. Before the introduction of effective vaccines, Hib was the leading cause of bacterial meningitis and other invasive bacterial disease among children less than 5 years of age; approximately one in 200 children developed invasive Hib disease before the age of 5 years.

Nearly all infections occurred among children less than 5 years of age, and approximately two thirds of all cases occurred among children less than 18 months of age.