The protective effect was enhanced by delivering the antibody in a nasal spray that disperses these molecules throughout the respiratory tract, where they stick to the slippery mucus lining to lie in wait for invading viral particles.

The engineered molecule is based on the IgM version of an immunoglobulin antibody, the generic first line of antibody defense against infection—but with an added structural feature that attaches to a very specific location on the influenza A surface to neutralize the virus.