Potential antigenic explanation for atypical H1N1 infections among middle-aged adults during the 2013–2014 influenza season

TLDR

Influenza usually causes higher disease burden in children and the elderly, yet the 2013–2014 season saw unusually high disease in middle‑aged adults. The study proposes incorporating new viral strains into seasonal influenza vaccines to elicit proper immunity across all ages. The authors recommend updating vaccine strains to match recent H1N1 mutations that evade immune responses in middle‑aged adults. Recent H1N1 strains carry a mutation that evades immune responses in middle‑aged adults, and current vaccine strains are predicted to be less effective in this group.

Abstract

Significance Influenza viruses typically cause a higher disease burden in children and the elderly, who have weaker immune systems. During the 2013–2014 influenza season, H1N1 viruses caused an unusually high level of disease in middle-aged adults. Here, we show that recent H1N1 strains possess a mutation that allows viruses to avoid immune responses elicited in middle-aged adults. We show that current vaccine strains elicit immune responses that are predicted to be less effective in some middle-aged adults. We suggest that new viral strains should be incorporated into seasonal influenza vaccines so that proper immunity is elicited in all humans, regardless of age and pre-exposure histories.