Neuraminidase characterisation reveals very low levels of antiviral resistance and the presence of mutations associated with reduced antibody effectiveness in the Irish influenza 2018/2019 season

Brehony, Carina; Dunford, Linda; Bennett, Charlene; O’Donnell, Joan; Domegan, Lisa; McNamara, Eleanor; De Gascun, Cillian F.

Neuraminidase inhibitor (NAI) resistance levels globally are currently low. However, as antivirals are increasingly being used, but even in the absence of selective pressure, resistance may increase or emerge. The neuraminidase (NA) genes from influenza viruses from the Irish 2018/2019 season were sequenced: 1/144 (0.7%) A(H1N1)pdm09 sequences harboured a substitution associated with highly-reduced susceptibility to NAIs. The very low NAI resistance we describe supports current Irish NAI use recommendations. However, continued monitoring is essential. NA characterisation also identified substitutions associated with reduced antibody effectiveness, thereby highlighting the potential of NA sequence surveillance as an additional tool for investigating influenza vaccine effectiveness (VE).