Circumvention of Herd Immunity during an Outbreak of Meningococcal Disease Could Be Correlated to Escape Mutation in theporAGene of Neisseria meningitidis

ABSTRACTMeningococcal strains isolated during an outbreak were shown to belong to the ET-5 complex and to harbor a mutation in the VR2 region of the porAgene. They were less susceptible to the bactericidal effect of normal human serum than was the ET-5 wild-type strain. These results are of concern, as PorA is a potential target in vaccine design.