Serogroup B meningococcal disease in persons previously vaccinated with a serogroup B meningococcal vaccine - United States, 2014-2019.

Since serogroup B meningococcal (MenB) vaccines became available in the United States, six serogroup B meningococcal disease cases have been reported in MenB-4C (n = 4) or MenB-FHbp (n = 2) recipients. Cases were identified and characterized through surveillance and health record review. All five available isolates were characterized using whole genome sequencing; four isolates (from MenB-4C recipients) were further characterized using flow cytometry, MenB-4C-induced serum bactericidal activity (SBA), and genetic Meningococcal Antigen Typing System (gMATS). Three patients were at increased meningococcal disease risk because of an outbreak or underlying medical conditions, and only four of the six patients had completed a full 2-dose MenB series. Isolates were available from 5 patients, and all contained sub-family A FHbp. The four isolates from MenB-4C recipients expressed NhbA but were mismatched for the other MenB-4C vaccine antigens. These four isolates were relatively resistant to MenB-4C-induced SBA, but predicted by gMATS to be covered. Overall, patient risk factors, incomplete vaccine series completion, waning immunity, and strain resistance to SBA likely contributed to disease in these six patients.