Incidence of bacterial meningitis continues to decline in U.S.

According to a report published online in the May 26 New England Journal of Medicine, the number of cases of bacterial meningitis in the United States has decreased in the past decade, especially in children.

Between 1986 and 1995, bacterial meningitis cases declined by 55 percent, which has largely been credited to the Hib conjugate vaccine for infants, introduced in 1990. Due to the introduction of the heptavalent protein-polysaccharide pneumococcal vaccine in 2000, invasive pneumococcal disease declined by 75 percent in children younger than age 5 between 1998 and 2007, reports Medscape.

"With the success of pneumococcal and Haemophilus influenzae type b (Hib) conjugate vaccines in reducing the risk of meningitis among young children, the burden of bacterial meningitis is now borne more by older adults," the study team notes, according to Medscape.

Overall, the incidence of meningitis fell by 31 percent from 2.00 cases per 100,000 population in 1998 to 1999 to 1.38 cases per 100,000 population in 2006 to 2007. Children younger than 2 months of age were the only age group not to decline in incidences of meningitis.

"Although intrapartum antibiotic prophylaxis has markedly reduced the risk of early-onset infection, such measures have had no effect on the risk of late-onset disease," Dr. Michael C. Thigpen and colleagues said, according to Medscape.

In the future, administration of group B streptococcus vaccines and new meningococcal vaccines could reduce the risk of bacterial meningitis among these infants. The median age of cases increased from 30.3 years in 1998 to 1999 to 41.9 years in 2006 to 2007. The authors estimate that between 2003 and 2007, 4,100 cases and 500 deaths from bacterial meningitis in the United States annually.