Nationally and in California, the shots are set to begin Thursday after a Centers for Disease Control and Prevention vaccine advisory committee issues recommendations Wednesday for using the two-dose vaccine in children as young as 12.
In California, Nevada, Oregon and Washington, the Western States Scientific Safety Review Workgroup is independently reviewing the U.S. Food and Drug Administration's emergency use authorization. It also is expected to make its decision Wednesday, clearing the way to start vaccinations across the state.
"California is ready to safely deliver vaccines to young people age 12 and older," said Dr. Erica Pan, the state epidemiologist.
FDA grants emergency use authorization for Pfizer COVID-19 vaccine for ages 12-15
"We all know how hard this has been for our youth," Pan said.
She said her own two children between 12 and 15 years old aren't looking forward to the shots, but are "really excited to be protected, to be able to spend more quality time with their friends and more time indoors and resuming their social lives."
The move comes as the state encourages schools to resume in-person teaching and remains on track to lift many virus-related restrictions by mid-June.
The state has the nation's lowest positivity rate at 1%, while 61% of those eligible have had at least one shot, said Dr. Mark Ghaly, the state's health secretary. More than 30% of youths ages 16 and 17 have at least one vaccination.
Experts say children must be vaccinated if the nation is to reach the 70% to 85% of the population needed to reach what is known as herd immunity.
California will not now require the coronavirus shots for students as it does other vaccines, Ghaly said, given the emergency use authorization. Minors also need consent from their parents or guardians in most cases.
But the state is working with local officials and community groups to encourage their use through things like targeted social media and "micro-influencers," the officials said.
That varies by location and does not necessarily include celebrities, but "trusted voices" like pediatricians and other healthcare workers, religious and school leaders.
How many people in your area are hesitant to get the COVID-19 vaccine?
"We know that young people have shouldered a significant burden throughout COVID in many ways - denied of certain activities, certain milestones, certain important events, shouldering additional degrees of anxiety and depression and other mental health and behavioral health impacts," Ghaly said.
He has a 13-year-old daughter who he said "has a lot of catching up to do" with her friends.
"The fact that we can now provide a certain degree of confidence and protection to those young people to start to resume activities, visit more with friends, visit their families and friends," Ghaly said. "I think it's a tremendous opportunity for that group to soft experience that sense of normalcy that they've been missing."
While most younger people don't experience the same severity of illness as adults if they are infected, Pan said they are not immune: California has had more than 500 severe cases among youths and 21 deaths, with a median age of 15.
Moderna and another U.S. company, Novavax, are testing their vaccines' use in adolescents, and Pfizer and Moderna are testing whether the vaccine works for even younger children.
Canada recently became the first to expand use to 12 and up. Across the U.S., a few cities began offering the vaccines Tuesday after officials there took the FDA's approval as authorization enough to begin giving the shots.
Orange and Sacramento counties began allowing families to pre-register for the shots last weekend. Within hours Sacramento County's site had 2,000 people registered, 90% of them for children 12-16, KCRA TV reported.
The state will end its color-coded multitiered level of restrictions in mid-June, but Madera, Mono and San Mateo moved to lower tiers Tuesday. The more populous counties of Orange and Santa Clara are poised to move to the least restrictive yellow tier as early as next week.
The Associated Press contributed to this report.