Impact of meningococcal B (4CMenB) vaccine on pharyngeal Neisseria meningitidis carriage density and persistence in adolescents

Mark McMillan, Luke Walters, Thomas Sullivan, Lex E X Leong, Mark Turra, Andrew Lawrence, Ann P Koehler, Adam Finn, Ross M Andrews, Helen S Marshall

Research output: Contribution to journalArticle (Academic Journal)peer-review

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BACKGROUND: Higher density of Neisseria meningitidis carriage may be associated with transmission of the meningococcus. Our aim was to establish the impact of 4CMenB vaccine on N. meningitidis carriage density.

METHODS: We compared 4CMenB vaccine to control among 913 South Australian students aged approximately 15-18 years in a cluster randomized trial who had N. meningitidis carriage at 12 months. Oropharyngeal swabs were collected at baseline and 12 months later to detect N. meningitidis carriage. Colony forming units per millilitre (CFU/ml) were estimated by generating a standard curve that plotted qPCR cycle threshold values against log-normalized CFU.

RESULTS: Among the 913 students with N. meningitidis carriage at 12 months, there was no difference in mean carriage density between the vaccinated (n=434, 3.80 log CFU/ml [SD 1.29]) and control group (n=479, 3.73 log CFU/ml [SD 1.30]; p=0.51). Higher N. meningitidis carriage density at baseline was associated with an increase in the odds of persistent carriage at 12 months (n=504, odds ratio per 1.0 log CFU/ml increase in density = 1.36 [95% CI, 1.17, 1.58], p<0.001). Students with baseline carriage who were vaccinated had decreased persistent N. meningitidis carriage at 12 months compared to unvaccinated students (82/186 [31%] vs 105/186 [43%], odds ratio 0.60 [95% CI, 0.40, 0.90], p=0.01).

CONCLUSION: 4CMenB vaccine did not reduce carriage density of N. meningitidis 12 months post vaccination, despite increased carriage clearance. Higher carriage density is likely to enable transmission through prolonged periods of population exposure.


Original languageEnglish
Article numberciaa610
JournalClinical Infectious Diseases
Early online date24 May 2020
Publication statusE-pub ahead of print - 24 May 2020

Bibliographical note

© The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail:


  • Carriage
  • Density
  • Vaccines
  • Risk factors
  • Public Health


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