All Santa Clara County residents age 75 and older are eligible to receive a COVID-19 vaccine effective immediately, vastly expanding the number of people eligible for immunization against the virus, county officials announced in a press conference Wednesday.

County Counsel James Williams said the county now has enough doses to extend eligibility beyond the previously narrow restrictions, which only permitted front-line health care workers and residents and staff of long-term care facilities to receive the vaccine. To date, an estimated 52,000 doses have already been administered, 31,000 of which were done by the county health system.

Residents interested in receiving a vaccine are being asked to go to sccfreevax.org to sign up for an appointment and go through a verification process to confirm eligibility, Williams said. Sutter Health, Stanford Health Care or Kaiser Permanente are expected to adopt the same eligibility requirements "soon," county officials said, and all three health care providers have individual links for scheduling vaccinations on the county’s web portal.

The county's vaccine eligibility, while greatly expanded, falls short of state guidelines released earlier Wednesday permitting counties to vaccinate all residents age 65 and older. Williams said the county is aware of the state's guidance, but simply does not have enough vaccine doses to accommodate that many residents. Over 300,000 residents in the county are over the age of 65. Once more doses have been received, the county will seek to reduce the age requirement to 65.

"We hope to be in a position to do that as well, as soon as we get vaccine supply here locally," Williams said.

The announcements by the state and the county are surprise moves that abandon a previous phased approach, which would have included workers in education, child care, emergency services, food and agriculture. The change of pace is driven by data that overwhelmingly shows older residents are far more likely to fall ill and die when they contract COVID-19.

Santa Clara County data shows 87.3% of the county's 1,011 COVID-19 deaths are among people ages 60 and older.

Williams cautioned that the county's vaccine web portal, sccfreevax.org, is the only county-run place to make arrangements to get the vaccine, and that other links and misinformation have caused problems in recent days. The result is that roughly 100 people have been turned away from vaccination appointments or were never eligible in the first place.

The county is moving forward with expanded vaccine eligibility despite many front-line health care workers who have still not received their first dose. Williams said the county has yet to receive enough doses from the state to vaccinate all health care workers in the county, but opening up further eligibility will ensure no vaccine goes unused.

The county must strike a balance between available supply and expanded eligibility, Williams said, which is made difficult because of quick changes in federal and state policies. What's more, the county has little knowledge of how many doses it's expecting to receive in the coming weeks, and does not have oversight of vaccine distribution to private pharmacies, Palo Alto Medical Foundation and Kaiser.

"We're operating in an environment that is not only changing, but that has very limited information," he said.

Find comprehensive coverage on the Midpeninsula's response to the new coronavirus by Palo Alto Online, the Mountain View Voice and the Almanac here.