Invasive meningococcal disease in England and Wales: implications for the introduction of new vaccines.

A number of meningococcal vaccines have either been recently licensed or are in late-phase clinical trials. To inform national vaccination policy, it is important to define the burden of disease and the potential impact of any new vaccine. This study describes the epidemiology of invasive meningococcal disease across all age groups in England and Wales for recent epidemiological years between 2006 and 2010. The Health Protection Agency (HPA) conducts enhanced national meningococcal surveillance through a combination of clinical and laboratory reporting. Between 2006/07 and 2010/11, the average annual incidence of invasive meningococcal disease across all age groups was 2.0/100,000. Capsular group B (MenB) accounted for 87% (4777/5471) cases, with an overall incidence of 1.8/100,000. The highest MenB incidence observed among infants (36.2/100,000) where cases increased from birth to 5 months of age then gradually declined. An annual average of 245 MenB cases occurred in infants (135 in those aged ≤ 6 months) representing 26% (and 14%) of all MenB cases, respectively. After infancy, MenB rates declined until the age of 12 years, rising to a second smaller peak at 18 years. MenB case fatality ratio (CFR) was 5.2% (247/4777 cases) overall and was highest among ≥ 65 year-olds (28/161; 17.4%). The largest number of deaths (n=125), however, occurred among <5 year-olds. Clonal complexes cc269 and cc41/44 each accounted for around a third of cases across the age groups. Other capsular groups rarely caused invasive disease, although capsular group Y (MenY) cases more than doubled from 35 in 2006/07 to 86 in 2010/11. Thus, universal meningococcal vaccination with an effective broad-spectrum formulation has potential to prevent most disease, particularly if the vaccine is immunogenic early in infancy, but, there is currently little justification for routine quadrivalent ACWY conjugate vaccination in the UK, although the increase in MenY disease warrants continued surveillance.

Epidemiology of meningococcal disease in England and Wales 1993/94 to 2003/04: contribution and experiences of the Meningococcal Reference Unit.

The laboratory confirmation of meningococcal disease and characterization of Neisseria meningitidis isolates was improved considerably in England and Wales by the Meningococcal Reference Unit between epidemiological years 1993/94 and 2003/04 to meet the challenge of increasing numbers of cases of clinical disease and the requirement for enhanced surveillance. Improved case ascertainment was made possible by the rapid introduction of an innovative centralized reference service for non-culture PCR-based DNA detection of meningococci utilizing the ctrA and siaD PCR assays, complemented by consistent phenotypic characterization of submitted isolates from culture-proven cases. This allowed the increased prevalence of serogroup C disease in specific age groups and the apparent associated increase in mortality from 1995/96 to 1999/00 to be defined, thereby prompting accelerated intervention with the newly licensed meningococcal serogroup C conjugate (MCC) vaccines into the under-25-year UK population (in November 1999). The continued increase in and predominance of serogroup B cases (1993/94 to 2000/01) were observed in conjunction with their diverse and changing phenotypic characteristics. Trends observed to be associated with the predominant phenotypic combinations of serogroup, serotype and sero-subtype were: a decline of both C : 2b and B : 2b meningococci, and a decline of B : 15 : P1.7,16 with a concomitant increase of B : 4 : P1.4 over the 11-year period. Detailed routine surveillance rapidly confirmed the introduction of W135 : 2a : P1.5,2 meningococci into the UK during 2000 and 2001. The importance of continued detailed surveillance of this important pathogen cannot be overestimated, both to monitor the effectiveness of the MCC vaccine and to identify changes within the meningococcal population that can inform the design of anti-serogroup B vaccines.