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Monday 25 June 2018
MenB epidemiology and new opportunities for prevention

This week's recommended reading is the article "Global epidemiology of serogroup B meningococcal disease and opportunities for prevention with novel recombinant protein vaccines", published last May on Human Vaccines & Immunotherapeutics.

Meningococcal disease (MD) is a major public health problem and remains a leading cause of meningitis and sepsis in many countries. Despite aggressive treatment, case fatality rates reach 10-20%; 10-20% of survivors will develop major long-term sequelae, and up to 36% of survivors may have one or more deficits in physical, cognitive, and psychological functioning. MD occurs in all age groups, although incidence rates are highest in young children and teenagers. Outbreaks of MD occur in an unpredictable manner in a number of settings where people gather.
Currently, six serogroups of Neisseria meningitidis (N. meningitidis), A, B, C, Y, W and X, are responsible for virtually all cases of disease reported worldwide.
Meningococci infect only humans and are transmitted from person to person. Acquisition of meningococci can lead to transient carriage, persistent colonization, or result in invasive disease. Asymptomatic nasopharyngeal carriage of N. meningitidis is common (5-10% in non-epidemic settings).
The European Centre for Disease Prevention and Control (ECDC) surveillance network has defined the criteria for invasive meningococcal disease. In Latin America, despite the lack of uniform criteria across countries, the Pan American Health Organization includes confirmed cases, probable, and suspected cases.
In North America, serogroups B (MenB), C (MenC) and, more recently, Y (MenY) have been the main serogroups causing MD, whereas in Africa, serogroup A was the main cause of epidemics until 15 years ago when serogroups C, W and X emerged. In Europe, serogroups B and Y, and, more recently, W (MenW) in some areas have predominated, although serogroup C remains prevalent in some countries lacking meningococcal C conjugate vaccination programs. In Latin America MenB, MenC and, during the past decade, MenW are currently responsible for the majority of reported MD cases.
Despite the availability, for several years, of safe and effective meningococcal conjugate vaccines against serogroups A, C, W and Y, only recently two serogroup B recombinant protein meningococcal vaccines were licensed and recommended for prevention of serogroup B MD (B-MD). The aim of the authors was to describe the global burden of B-MD, briefly review the data on vaccines development, and world experience with these vaccines, including the first estimates of effectiveness, safety and impact data, based on the use of these vaccines in routine immunization programs and for outbreak control.
The first attempts to prevent MD by vaccination occurred at the beginning of the twentieth century. Meningococcal A, C, W and Y conjugated polysaccharide vaccines have been developed and licensed, in different formulations, since the year 2000. The antigenic mimicry between serogroup B polysaccharide and human neural tissue antigens curtailed development of polysaccharide-based vaccines against this pathogen. The solution was found in targeting outer membrane proteins (OMVs). These vaccines proved to be immunogenic, protective, and effective in controlling regional outbreaks. The significant variability of porins among strains circulating worldwide precluded this strategy for universal vaccination. 4CMenB (Bexsero®, GlaxoSmithKline) and bivalent rLP2086 (Trumenba®, Pfizer) are now licensed. The authors underlined that the potential cross-protection against non-B meningococcal strains has been described for 4CMenB, but not yet for rLP2086. For both vaccines, the impact of vaccination on nasopharyngeal carriage is uncertain. Both vaccines are relatively reactogenic and they are currently of relatively high cost. Massive vaccination campaigns can be implemented for outbreak control.
The authors concluded warning that there is no current preference for one of the two available vaccines according to CDC recommendations, and vaccine interchangeability cannot currently be endorsed. Whether development of the vaccine in adolescents would reduce carriage and result in herd protection, as seen following conjugate vaccine programs, remains an unanswered question at the time of writing.

AUTHORS: Villena R., Safadi M.A.P., Valenzuela M.T., Torres J.P., Finn A., O'Ryan M.

Click here to go to the article!