Research is being conducted on the effectiveness of covid-19 vaccines, including the BNT162b2 XBB vaccine, in preventing severe covid-19 outcomes. The vaccines' effectiveness in reducing hospitalizations and medically attended cases among certain populations, such as us veterans and adults aged 65 and older, is being studied. The reported effectiveness of these vaccines varies, with one study finding a specific vaccine to be 68% effective against hospitalization, although the overall findings are not entirely consistent across different studies.