Lance Cpl. Melissa A. Latty [Public domain] via Wikimedia CommonsSeveral influenza virus strains infect humans, including some that are highly pathogenic and potential pandemic agents. Influenza vaccines are used to reduce exposure, illness and health care costs. Hemagglutinin, the most common vaccine target, is highly mutable, however, so vaccines must be reformulated each year to address emerging influenza strains. A ‘universal’ vaccine that protects against multiple influenza types would minimize the need to reformulate vaccines and revaccinate susceptible individuals, leading to substantial public health improvements and cost savings.