Seasonal trivalent inactivated influenza vaccine does not protect against newly emerging variants of influenza A (H3N2v) virus in ferrets

Abstract

The recent increase in human cases of influenza A H3N2 variant virus [A(H3N2)v] highlights the need to assess whether seasonal influenza vaccination provides cross-protection against A(H3N2)v virus. Our data demonstrate that the 2011-2012 trivalent inactivated influenza vaccine (TIV) protected ferrets against homologous H3N2 virus challenge but provided minimal to no protection against A(H3N2)v virus. The complete absence of specific hemagglutination inhibition antibody response to A(H3N2)v is consistent with the poor cross-protection observed among TIV-immune animals.

Fig 1

TIV vaccine efficacy following challenge with A/Perth/16/2009 (Perth/16) or A/Indiana/08/11 (IN/11) virus. Nasal washes were collected with 1 ml of PBS on even-numbered days postchallenge. Titers were determined by standard plaque assay on MDCK cells from challenge with A/Perth/16/2009 (A) or A/Indiana/08/11 (B) virus. Bars display average values, with standard deviation shown as error bars, with 5 or 6 ferrets per group. Differences in viral titers were analyzed by the Student t test (*, P ≤ 0.05; **, P ≤ 0.01).