WASHINGTON (AP) — Hospitals are gearing up to test if a century-old treatment used to fight off pre-vaccine epidemics of flu, measles and other infections might work for COVID-19, too — using blood donated from patients who’ve recovered. Doctors in China attempted the first treatments using infusions of donated plasma. Now U.S. hospitals are seeking government permission for formal studies to test antibody-rich plasma in the sick. They also want to test if the infusions could offer offer temporary, vaccine-like protection to people at high risk, such as hospital workers. History suggests it could work but there’s no guarantee.