Solis' order will allow residents 65 and older to start making vaccine appointments starting Thursday.
"If we are to ever get out of this dark winter, it is critical that we make headway vaccinating people 65 years of age and older as soon as possible - in line with Governor Gavin Newsom's recommendations," Solis said in a statement.
"That is why I signed an Executive Order today directing the County's Department of Public Health to make COVID-19 vaccinations appointments available to residents 65 years of age and older, beginning on January 21, 2021 - this is to allow for public health officials to adequately prepare for the rollout of the vaccine to this population."
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The state opened vaccine eligibility to people 65 and older earlier in the month, but L.A. County is lagging behind other Southern California counties in opening up vaccinations to that group.
County Public Health Director Barbara Ferrer last week said the county would not offer vaccines to people 65 and older until vaccinations of front-line health care workers were completed. That process was expected to last until the end of the month.
Ferrer noted that expanding the availability of the shots was largely dependent on the local supply of vaccines.
There was no immediate word on what impact Solis' order would have on the county's vaccine supply, and its ability to complete vaccinations of health care workers.
Supply of the vaccine is already limited, particularly following word last week that a federal stockpile of doses had already vanished.
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Two county supervisors had been pushing for the expansion of COVID-19 vaccinations for people 65 and older.
Supervisors Kathryn Barger and Janice Hahn have called for the distribution process to be expedited to include that vulnerable segment of the county's population as soon as possible. Hahn applauded Solis' order shortly after the announcement was made, and both Hahn and Barger urged residents to make an appointment at vaccinatelacounty.com.
VACCINE UPDATE: L.A. County residents over 65 are now able to make vaccine appointments. Thank you to my colleagues for your parternship and advocacy for our vulnerable communities. Make an appointment for as soon as 1/21 at https://t.co/cdmkKeTHXH. pic.twitter.com/GfQeQ8xWDs— Supervisor Kathryn Barger (@kathrynbarger) January 19, 2021
L.A. County will open five mass vaccination sites across the region Tuesday. This is in addition to the vaccination site at Dodger Stadium, which opened Friday.
Meanwhile, a new study from Cedars-Sinai shows a new COVID-19 variant, CAL.20C, was found in more than one-third of coronavirus cases in L.A, and may be partly responsible for the recent dramatic increase in cases.
City News Service contributed to this report.