From the CDC

Encouraging news from the CDC:  "Haemophilus influenzae type b (Hib) was the leading cause of bacterial meningitis and a major cause of other serious invasive diseases among children aged <5 years in the United States before Hib conjugate vaccines became available in 1988."    

 "In 1991, all infants starting at age 2 months were recommended to receive Hib conjugate vaccines; by 1996, incidence of Hib invasive disease (i.e., illness clinically compatible with invasive disease, such as meningitis or sepsis, with isolation of the bacterium from a normally sterile site) among children aged <5 years had declined by >99%."     Hib invasive disease remains at these low levels, except in communities with unusually low vaccination rates.