By Alice Park January 2, 2025 1:29 PM EST A 13-year-old girl in Canada became so sick with H5N1 , or bird flu, in late 2024 that she had to be put on a ventilator. Around the same time, a senior in Louisiana was diagnosed with the first "severe" case in the U.S. As bird flu continues to ramp up, many are wondering what tools—namely, vaccines—we have to fight it if such intervention becomes necessary. “Public-health and infectious disease folks around the world are watching bird flu very, very