Enhanced genetic characterization of influenza A(H3N2) viruses and vaccine effectiveness by genetic group, 2014-2015.

Flannery B1, Zimmerman RK2, Gubareva LV1, Garten RJ1, Chung JR3, Nowalk MP2, Jackson ML4, Jackson LA4, Monto AS5, Ohmit SE5, Belongia EA6,McLean HQ6, Gaglani M7, Piedra PA8, Mishin VP1, Chesnokov AP1, Spencer S3, Thaker SN1, Barnes JR1, Foust A1, Sessions W1, Xu X1, Katz J1, Fry AM1.

Author information

Abstract

BACKGROUND:

During the 2014-15 US influenza season, expanded genetic characterization of circulating influenza A(H3N2) viruses was used to assess the impact of genetic variability of influenza A(H3N2) viruses on influenza vaccine effectiveness (VE).

METHODS:

A novel pyrosequencing assay was used to determine genetic group based on hemagglutinin (HA) gene sequences of influenza A(H3N2) viruses from patients enrolled US Flu Vaccine Effectiveness network sites. Vaccine effectiveness was estimated using a test-negative design comparing vaccination among patients infected with influenza A(H3N2) viruses and uninfected patients.

RESULTS:

Among 9710 enrollees, 1868 (19%) tested positive for influenza A(H3N2); genetic characterization of 1397 viruses showed 1134 (81%) belonged to one HA genetic group (3C.2a) of antigenically drifted H3N2 viruses. Effectiveness of 2014-15 influenza vaccination varied by A(H3N2) genetic group from 1% (95% confidence interval [CI], -14% to 14%) against illness caused by antigenically drifted A(H3N2) group 3C.2a viruses versus 44% (95% CI, 16% to 63%) against illness caused by vaccine-like A(H3N2) group 3C.3b viruses.

CONCLUSION:

Effectiveness of 2014-15 influenza vaccination varied by genetic group of influenza A(H3N2) virus. Changes in hemagglutinin genes related to antigenic drift were associated with reduced vaccine effectiveness.

Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.