Biotech firms make new influenza vaccines each year to protect the public from the rapidly adapting flu virus. Vaccine makers could avoid that annual task if they could come up with antigens that stimulate immune responses to multiple flu strains. Last week, two research groups reported progress toward the goal of a universal flu vaccine. Both groups focused their efforts on harnessing and improving hemagglutinin (HA) stems—conserved regions of glycoproteins on the viral surface—to elicit a protective immune response in vaccinated animals. Researchers at the Dutch biotechnology firm Crucell and Scripps Research Institute developed a trimeric “mini-HA stem” and found that it protects mice and nonhuman primates from infection by multiple influenza strains, including H1N1 swine flu and H5N1 avian flu (Science 2015, DOI: 10.1126/science.aac7263). Another group, at the National Institutes of Health, developed an HA-stem nanoparticle and tested its efficacy in mice and ferrets. The treatment protected all mice and the majority of ferrets against multiple flu strains (Nat. Med. 2015, DOI: 10.1038/nm.3927). Both teams are now refining their prototype vaccines and plan to further test their strategies against additional flu strains.