Vaccinemakers largely rely on an old technique that exposes ferrets—which differ from humans—to candidate vaccine strains and then assesses whether they can stop viral isolates from people naturally infected with the circulating strains. The BC Centre's Skowronski says many influenza researchers are hesitant to discuss problems with the vaccine "because they are afraid of being tainted with the antivaccine brush. I am going to make universal influenza vaccine my priority over the next couple years," Fauci says. Further, complicating the picture is the immunologic legacy of multiple exposures to influenza each year—from the vaccine and from wild-type virus. Skowronski thinks the field must more aggressively pursue a universal influenza vaccine