On Sept. 15, 2023, researchers at the National Institute of Allergy and Infectious Diseases announced they had begun a Phase 1 trial to test the safety and immunogenicity of a new experimental universal influenza vaccine. The vaccine is designed to induce an immune response against many different influenza virus strains by displaying part of the influenza virus hemagglutinin (HA) protein on self-assembling nanoparticle scaffolds.

Exposure to these harmless fragments of virus proteins prepares the immune system to recognize and fight against the actual virus, in case of a flu infection. Earlier versions of this investigational vaccine contained HA from four strains of flu; the new vaccine has proteins from six strains.