4CMenB vaccine effectiveness: reasons for optimism.

Preventing invasive meningococcal disease (IMD) caused by the bacterial pathogen Neisseria meningitidis is of critical public health importance given the sudden onset of symptoms, rapid progression to serious disease, and high risk of mortality even among previously healthy individuals1,2. The burden of IMD has been reduced in many parts of the world through extensive public health efforts, most notably following the introduction of conjugate group C vaccines in the United Kingdom (UK) in 19993, and conjugate group A vaccines in the African meningitis belt beginning in 20104. Yet, developing vaccines to protect against the diversity of disease-causing meningococcal B (MenB) strains has been challenging. The first vaccines designed to be broadly immunogenic against multiple MenB strains became available only recently,5,6 with the 4CMenB vaccine (also known as Bexsero® [GSK]) licensed in Europe in 2013. The UK became the first country to introduce 4CMenB into a national infant immunization program in September 2015. UK health authorities recommend a reduced 2-dose priming schedule at 2and 4-months and a booster dose at 12 months of age for all infants born since July 2015, plus an opportunistic catch-up program for infants born in May or June 20157,8.