The changing epidemiology of meningococcal disease in the United States, 1992-1996

Meningococcal disease prevention and control strategies for practice-based physicians (Addendum: recommendations for college students). Committee on Infectious Diseases

The numbers of reported cases of meningococcal disease in 15- to 24-year-olds and outbreaks of meningococcal serogroup C disease, including outbreaks in schools and other institutions, have increased during the past decade. In response to outbreaks on college campuses, the American College Health Association has taken an increasingly proactive role in alerting college students and their parents to the risk of this disease and informing them about the availability of an effective vaccine. Recent epidemiologic studies have demonstrated an increased risk of disease in college students living in dormitories, particularly among freshmen, compared with similarly aged persons in the general population. At least 60% of these cases are potentially preventable by vaccination with the quadrivalent meningococcal A, C, Y, and W-135 polysaccharide vaccine. These findings support immunization of college students, particularly freshmen living in dormitories. Hence, college students and their parents should be informed by health care professionals at routine prematriculation visits and during college matriculation of the risk of meningococcal disease and potential benefits of immunization. Vaccine should be made available to those requesting immunization. College and university health services also should facilitate implementation of educational programs concerning meningococcal disease and availability of immunization services.

Distribution of Neisseria meningitidis serogroup B serosubtypes and serotypes circulating in the United States. The Active Bacterial Core Surveillance Team

Because the Neisseria meningitidis serogroup B (NMSB) capsule is poorly immunogenic in humans, immunization strategies have focused on noncapsular antigens. Both PorA and to a lesser extent PorB are noncapsular protein antigens capable of inducing protective bactericidal antibodies, and vaccines based on the outer membrane protein (OMP) components of serogroup B meningococci have been shown to be effective in clinical trials. Multiple PorA antigens seem to be needed to prevent endemic meningococcal disease around the world, and a hexavalent PorA-based meningococcal vaccine has recently been developed in The Netherlands. To evaluate the distribution of NMSB PorA and PorB antigens in the United States, serosubtyping and serotyping were done on 444 NMSB strains isolated in the active surveillance areas of the United States (total population, 32 million) during the period 1992 to 1998. A total of 244 strains were isolated from sporadic cases of meningococcal disease, and 200 strains were isolated from an epidemic in Oregon. A panel of 16 mouse monoclonal antibodies reactive with PorA and 15 monoclonal antibodies reactive with PorB were used. Among the NMSB isolates obtained from sporadic cases, the most prevalent serosubtypes were P1.7,16 (14.3%), P1.19,15 (9.8%), P1.7,1 (8.6%), P1.5,2 (7.8%), P1. 22a, 14 (7.8%), and P1.14 (5.3%) and the most prevalent serotypes were 4,7 (27.5%), 15 (16%), 14 (8.6%), 10 (6.1%), 1 (4.9%), and 2a (3.7%). A multivalent PorA-based OMP vaccine aimed at the six most prevalent serosubtypes could have targeted about half of the sporadic cases of NMSB disease that occurred between 1992 and 1998 in the surveillance areas. Twenty serosubtypes would have had to be included in a multivalent vaccine to achieve 80% coverage of strains causing sporadic disease. The relatively large number of isolates that did not react with murine monoclonal antibodies indicates that DNA sequence-based variable region typing of NMSB will be necessary to provide precise information on the distribution and diversity of PorA antigens and correlation with nonserosubtypeable isolates. The high degree of variability observed in the PorA and PorB proteins of NMSB in the United States suggests that vaccine strategies not based on OMPs should be further investigated.

Update on Haemophilus influenzae serotype b and meningococcal vaccines

Use of conjugate Haemophilus influenzae type b (Hib) vaccines has resulted in the near elimination of Hib invasive disease among infants in the United States in only 10 years, which places this intervention among the most notable public health achievements of the past decade. This has radically altered our perception of the major causes of bacterial meningitis and invasive bacterial disease among children, increasing the prominence of meningococcal disease as an important cause of childhood and adult meningitis and leading researchers to apply the same conjugate technology to the development of improved vaccines for Neisseria meningitidis. Use of conjugated meningococcal vaccines against serogroups A, C, Y, and W-135 are expected to offer the possibility of better control of sporadic disease and outbreaks throughout developed and developing countries within the next 5 years.

Preventing meningococcal infection in college students

The incidence of invasive meningococcal disease in adolescents and young adults of high school and college age has recently increased in the United States. Recent studies indicate that certain groups of college students are at increased risk. This has led to the recent Advisory Committee Immunization Practices recommendation that college freshman dormitory residents be provided information about meningococcal infection and the benefits of vaccination. Future studies will need to focus on the potential vaccine prevention of the increased risk of meningococcal infection in persons of high school age, particularly as new conjugate meningococcal vaccines become available.