Toward a universal flu vaccine
Influenza virus infections pose a major public health threat, accounting for 3.5 million severe infections and more than 400,000 deaths globally each year (1). Most seasonal vaccines consist of inactivated influenza virus components, which induce antibody responses against immunodominant epitopes in the viral hemagglutinin (HA) and neuraminidase (NA) proteins. The genes that encode HA and NA undergo continuous changes (antigenic drift), which necessitates annual reformulation and revaccination, leading to reduced vaccine coverage. Vaccine effectiveness thus varies depending on the accuracy of preseasonal predictions, and inactivated seasonal influenza vaccines generally provide insufficient protection against pandemic viruses (2). On page 869 of this issue, Wang et al. (3) explore an unconventional strategy to overcome these shortcomings by complementing inactivated influenza virus vaccines with an adjuvant that triggers mucosal immune responses to elicit rapid protection against a variety of influenza virus strains in mice and ferrets.