Changes in the population structure of invasive Neisseria meningitidis in the United States after quadrivalent meningococcal conjugate vaccine licensure.

Wang X1, Shutt KA2, Vuong JT1, Cohn A1, MacNeil J1, Schmink S1, Plikaytis B1, Messonnier NE1, Harrison LH2, Clark TA1, Mayer LW1.

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Abstract

BACKGROUND:

Meningococcal conjugate vaccines (MenACWY) against serogroups A, C, W and Y are recommended for routine use in adolescents aged 11-18 years. Impact of these vaccines on meningococcal population structure in the US remained to be evaluated.

METHODS:

Meningococcal isolates from 2006-10 (post-MenACWY) collected through Active Bacterial Core surveillance (ABCs) were characterized; serogroup distribution and molecular features of these isolates were compared to previously published data on ABCs isolates from 2000-05 (pre-MenACWY). p values were generated using chi-squared statistics and exact methods.

RESULTS:

There was a significant change (p<0.05) in serogroup distribution among all age groups between the two periods. A small proportion of isolates has shown evidence of capsular switching in both periods. Between the two periods, significant changes were observed in the distribution of PorA, FetA, and strain genotypes among vaccine and non-vaccine serogroups.

CONCLUSIONS:

The population structure of U.S. meningococcal isolates is dynamic; some changes occurred over time but the basic structure remained. Vaccine-induced serogroup replacement was not observed, although a small proportion of isolates had undergone capsule switching possibly driven by non-vaccine mediated selection. Changes in the distribution of molecular features are likely due to horizontal gene transfer and changes in serogroup distribution.

Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.