SAN FRANCISCO (CBS SF/AP) — State health officials have eased the strict guidelines on who qualifies for a COVID booster shot, allowing all Californians who feel they are at risk to receive a dose of additional protection before attending large family gatherings planned for the Thanksgiving holiday.

In letter to all local health jurisdictions and providers on Nov. 9, Dr. Tomás J. Aragón, the state public health officer, announced that anyone who wanted one can now receive a booster shot.

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Eligibility for the shots had been limited to Californians age 65 and older, whose jobs could lead to exposure to the virus and to those who have underlying medical conditions.

Now those restrictions have been lifted.

“Allow patients to self-determine their risk of exposure,” Aragón said in the letter. “Do not turn a patient away who is requesting a booster if: The patient is 18 or over and has met the 6-month original vaccination series time period for the Moderna or Pfizer vaccine or it has been at least 2 months since their J&J vaccine.”

The announcement came as Gov. Gavin Newsom and others warned of a possible surge in cases over the holidays.

While statewide hospitalizations have fallen by about half since a summer peak at the end of August, they have started creeping up in some areas, particularly the Central Valley and portions of Southern California including Los Angeles and San Bernardino counties.

“We’ve seen some signs that suggest concerns,” Newsom said.

California earlier this fall had the nation’s lowest case rate but is now 16th, he said, while the positivity rate for those tested is 2.3% after falling below 1% in June.

Newsom signed an executive order that through March 31 will continue to allow out-of-state medical workers to treat patients in California and allow emergency medical technicians and others to keep administering vaccines and providing other related services. It also keeps flexibility for health care facilities, for instance allowing parking lots to be used for vaccination sites.

Beyond the upward trend in certain parts of the state, state health officials said they are generally apprehensive because colder weather will keep people inside. There will be more holiday mingling at a time when vaccine and natural immunity acquired months ago will begin to wane unless more people get booster shots.

“We have learned over the last two years that COVID-19 takes advantage when we put our guard down,” Newsom’s health department said in a statement.

The state’s own models still predict an overall decline in hospitalizations and intensive care cases over the next month. And the statewide R-effective that measures infection rates also continues dropping and now is at 0.85. Anything below 1 means the number of infected persons will decrease.

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The concern is that even those who are vaccinated may be more vulnerable to the extremely contagious delta variant unless many more people get booster shots, which currently are lagging, said Dr. Kirsten Bibbins-Domingo, a professor of epidemiology at the University of California, San Francisco.

Moreover, California is so large and geographically and demographically diverse that conditions are “wildly variable,” which also affects the state’s modeling at a time when many have grown tired of precautions like masking and isolating, she said.

“There are plenty of local models that do show rising hospitalizations that we are already starting to see in local environments,” Bibbins-Domingo said. “It is a little bit of a race, and it sort of depends on whether waning immunity wins or whether us getting boosters into people wins.”

Dr. Lee Riley, chairman of the Division of Infectious Disease and Vaccinology at the University of California, Berkeley, School of Public Health, said the increase may be due to complacency as businesses reopen and people let down their guard, though the number of cases is nowhere close to the summer surge.

“I think it is a good idea to be prepared because we’ve been burned several times before when we didn’t do that, (although) I do feel a little more optimistic now than before,” he said.

Newsom used a visit to a COVID-19 vaccine and flu shot clinic in Los Angeles to urge residents, including newly eligible children 5 to 11, to get vaccinated. He also urged booster shots for those who are eligible.

Newsom, who got a booster on Oct. 27, said it has become evident from the experience of Europe and other U.S. states that the coronavirus has a seasonal aspect that can lead to an increase in infections.

He used apocalyptical reminders of last year’s winter surge that had officials buying body bags and bringing mobile morgues to Southern California as infections surged 10-fold over eight weeks and overwhelmed many hospitals.

“Thousands of people lost their lives, thousands of people on life support, close to death,” he said. That’s why state officials are “doing everything in our power to prepare.”

Brian Ferguson, a spokesman for the Governor’s Office of Emergency Services, said the state’s preparations since the start of the pandemic have “put the state in a much better place to withstand any surge that occurs this winter.”

The state “has all of the expanded capacity from the mobile field hospitals and supply caches that were acquired during the pandemic as well as the contracts to bring in nursing and medical personnel that were put in place previously,” Ferguson said.

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Stephanie Roberson, government relations director of the California Nurses Association, said the Health and Human Services Agency “has been working super closely with the hospitals to make sure that they are getting staff.”