Background The UK introduced 4CMenB—a multicomponent vaccine against serogroup B meningococcal disease—into the national infant immunisation programme in September, 2015. The Meningococcal Antigen Typing System (MATS) was used to estimate coverage by 4CMenB of invasive meningococcal group B isolates obtained during 2007–08 in England and Wales (MATS coverage). We aimed to repeat the MATS survey for invasive meningococcal group B isolates obtained during 2014–15, before 4CMenB introduction; compare strain coverage between 2007–08 and 2014–15; and investigate associations between MATS coverage, age, region, and disease outcomes. Methods Invasive serogroup B meningococcal isolates from cases in England, Wales, and Northern Ireland during 2014–15 were assayed using MATS and compared with 2007–08 data. MATS coverage was assessed by geographical region and age group. Clinical characteristics, risk factors, and outcomes were assessed according to MATS coverage for 2014–15 English cases. Findings In 2014–15, 165 of 251 (66%; 95% CI 52–80) meningococcal group B isolates were estimated by MATS to be covered by 4CMenB, compared with 391 of 535 (73%; 95% CI 57–87) in 2007–08. The proportion of MATS-positive isolates with one vaccine antigen increased from 23% (122 of 535) in 2007–08 to 31% (78 of 251) in 2014–15, whereas the proportion with more than one antigen fell from 50% (269 of 535) to 35% (87 of 251). This effect reflected changes in circulating strains, particularly ST-269 clonal complex strains. MATS coverage increased with age, varied by geographical region, and was associated with more severe disease. Interpretation In 2014–15, two-thirds of meningococcal group B isolates were predicted to be covered by 4CMenB. Temporal changes in MATS coverage underscore the need for continued monitoring of antigen expression and diversity, particularly in countries with 4CMenB programmes. Funding Public Health England, GlaxoSmithKline.
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