In Fresno County, eligibility began nearly a week ago, but health officials say the turnout didn't meet expectations.
"We are only seeing about 50% of our slots being filled at the fairgrounds and we are also checking in with other mass vaccinations sites, and their slots are about 50% or less," says Fresno County Division Health Manager Joe Prado.
Tulare County health officials say they're experiencing the opposite. They opened eligibility to those 16 and older on March 31.
Carrie Monteiro with the Health and Human Services Agency says numbers have stayed consistently high.
"We have been seeing a favorable result since we expanded eligibility," she said. "The number of vaccinations keeps increasing week by week in Tulare County."
But some counties might not have enough doses for everyone. Mariposa County Health officials say they're in urgent need of the Pfizer vaccine.
Without it, they can't vaccinate anyone under the age of 18. They're now reaching out to neighboring counties for help.
"To see if we can get some Pfizer from them and swap some Moderna for Pfizer," says Mariposa County Public Health Officer Eric Sergienko.
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Health officials anticipate the halt of the Johnson and Johnson vaccine to cause some hesitancy in getting vaccinated.
Prado says the same thing happened when the Moderna vaccine was put on pause.
But he's urging people to get informed and get the shot.
"You may have a family member who has been vaccinated, have a conversation with them," he said. "Talk to your neighbor, talk to your friend, talk to somebody at church."
Governor Gavin Newsom is expected to address the state's vaccination progress on Thursday around 10:15 am.