In 1985, when the CDC’s Advisory Committee on Immunization Practices (ACIP) made its first recommendations on the recently licensed tetravalent meningococcal polysaccharide vaccine targeting serogroups A, C, Y, and W-135 for use in persons with functional or anatomic asplenia or terminal complement component deficiencies, serogroup B accounted for between 50 to 55 percent of all meningococcal disease. Meningococcal serogroup C accounted for 20-25 percent, followed by serogroup W-135 at 15 percent, serogroup Y at 10 percent and serogroup A at 1-2 percent. At this time, there were 2,479 reported cases of meningococcal disease, and the disease rate was reported to be at 1.04 cases per 100,000 population.
There was an average of 2,400 cases of meningococcal disease reported yearly between 1992 and 1996, with disease rates higher among infants and adults 30 years of age and older. Serogroup C accounted for 35 percent of cases, followed by serogroup B at 32 percent, and serogroup Y at 26 percent. Meningococcal polysaccharide vaccines were administered primarily during an outbreak of the disease as the vaccine offered only short-term protection and was ineffective in children under the age of two.
From 1998 to 2007, and prior to the introduction of meningococcal conjugate vaccines targeting serogroups A, C, Y, and W-135, meningococcal disease rates continued to decrease. By 2007, there were 1,077 reported cases of meningococcal disease, down significantly from the 2,725 cases reported in 1998. Disease rates dropped from 0.92 cases per 100,000 population in 1998 to only 0.33 cases per 100,000 population by 2007. Researchers reported that while they could not offer any explanation for the significant decrease in the number of cases of meningococcal disease, they acknowledged that the newly licensed meningococcal conjugate vaccine was not responsible for the reduction in disease rates.
Meningococcal disease from all serogroups declined again from 1,172 reported cases in 2008 to 372 cases in 2015. Serogroup B invasive disease also declined significantly during the same time period even without the availability of a meningococcal serogroup B vaccine. Again, meningococcal disease researchers could not offer any explanation to account for the decrease in the number of reported meningococcal serogroup B disease cases during this time period.
In 2020, there were 235 reported cases and 23 deaths attributed to meningococcal disease. Of the reported cases, serogroup B accounted for 55 cases and 6 deaths; Serogroup C accounted for 54 cases and 2 deaths; Serogroup W accounted for 15 cases and 3 deaths; serogroup Y accounted for 50 cases and 6 deaths; nongroupable serogroups accounted for 26 cases and 3 deaths; and unknown serogroups accounted for 35 cases and 3 deaths.
In January 2022, an outbreak of serogroup C meningococcal disease began, with most cases reported among men who have sex with other men. As of January 2023, there have been 43 cases and nine deaths associated with this outbreak, with thirty-five percent of cases occurring in persons with HIV illness. All cases have occurred in adults between the ages of 20 and 77.
Globally, the World Health Organization (WHO) states that there is an inadequate surveillance system in place to reliably report on the burden of meningococcal disease. This results in a lack of accurate estimates in the number of cases that occur annually. The sub-Saharan desert, an area stretching from Ethiopia in the east to Senegal in the west, has historically accounted for the highest number of meningococcal meningitis cases worldwide. Often referred to as the meningitis belt, WHO reports that approximately 30,000 cases occur annually. Untreated cases of meningococcal disease are reported to have a fatality rate of approximately 50 percent and over 10 percent of individuals who develop the disease suffer severe long-term residual health problems as a result.
