Why California is moving to an age-based system for coronavirus vaccine priority FacebookTwitterEmail Marin Community Clinic staff and medics with Marin County Fire work at separate tables to prepare and administer the Pfizer coronavirus vaccine to staff at the Tamalpais Marin assisted living facility in Greenbrae in December. Nursing home staff were among the first people to be vaccinated in California, along with health care workers.Jessica Christian / The Chronicle 2020 California will adopt an age-based system to vaccinate residents, a shift away from the state’s initial strategy of weighing job-based risk, that health officials hope will speed up and simplify the vaccination process.