The number of reported cases of vaccine-preventable diseases has generally decreased over the past several decades. In 2007, there were no reported cases of diphtheria or polio in the United States, and no cases of tetanus among children under 5 years of age. Among children in this age group, there were no reported cases of acquired rubella and only one case of congenital rubella.
From 2006 to 2007, the number of reported cases of hepatitis A, pertussis, and mumps decreased among children under 5 years of age. The overall incidence of hepatitis A began dropping dramatically once routine vaccination for children living in high-risk areas was recommended beginning in 1996, and in 2005, the Centers for Disease Control and Prevention (CDC) instituted the recommendation that all children be immunized for hepatitis A starting at 1 year of age. The latter recommendation was made because two-thirds of cases were occurring in States where the vaccine was not currently recommended. With regard to pertussis, the number of cases among young children decreased nearly 50 percent from 2005 to 2006, with a smaller increase of 18 percent from 2006 to 2007. According to the CDC, pertussis occurs cyclically and decreases in the incidence of the disease may not be due to increases in immunization rates. The highest reported rate occurred among infants under 6 months of age, a population that is too young to be fully vaccinated. Following a 2006 outbreak in Midwestern states - the largest in more than 20 years - reported cases of mumps decreased 72 percent. In response to the outbreak, the CDC updated criteria for mumps immunity and vaccination recommendations. Reported cases of hepatitis B and H. Influenzae remained relatively unchanged from 2006 to 2007.