 Invasive meningococcal disease is rare but often vaccine preventable. Evaluation of vaccine effectiveness is impractical due to low disease incidence, so protection is estimated using serum bactericidal antibody, SBA, assays with baby rabbit complement, RSBA. Post-licensure effectiveness data for serogroup C conjugate vaccine suggests that RSBA tight is greater than or equal to eight other correlator protection for this serogroup, but no thresholds have been formally established for other serogroups. Studies evaluating MNACWYTT, Nimenryx registered trademark symbol, Pfizer Inc., Sandwich, UK Immunogenicity suggests that RSBA may be more appropriate for these measurements. This article was authored by Jamie Findlow, Paul Barmer, and Ray Borough.