On Jan. 14, 2005, the first meningococcal polysaccharide (Serogroups A, C, Y and W-135) diphtheria toxoid conjugate vaccine (Menactra by Sanofi Pasteur) was licensed in the U.S. for 11- to 55-year-olds and is now recommended for the routine immunization of adolescents and other high-risk groups. .

The role of the meningococcus as a cause of bacterial meningitis has become more pronounced in recent years with the declines in meningitis caused by Haemophilus influenzae type b and Streptococcus pneumoniae because of the introduction of new conjugate vaccines, Listeria because of efforts to reduce the contamination of food with L. monocytogenes, and group B streptococcus because of the use of intrapartum chemoprophylaxis in selected women

Neisseria meningitidis is the leading cause of bacterial meningitis in the United States and worldwide. A serogroup A/C/W-135/Y polysaccharide meningococcal vaccine has been licensed in the United States since 1981 but has not been used universally outside of the military.