Many Bay Area hospitals are vigorously enforcing a new mandate that health care workers throughout Alameda, Contra Costa and Santa Clara counties get a flu shot or don a mask during the flu season. Comprehensive numbers are not yet available, but some institutions are reporting dramatic increases in employee vaccination rates. Many hospitals have set up flu stations with employee masks at entrances to buildings and are using stickers on employee badges to identify those who have had a shot. Stations with sanitizers and masks have also been set up for patients. The goal of the mandate is to protect patients who are most at risk, including infants, the elderly and those with weakened immune systems.