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SAN DIEGO — County health officials say they are prepared to start vaccinating children ages 12 to 15 as soon as Thursday morning.

Local health leaders expect to hear from the California Department of Public Health by end of day on Wednesday on the timing of offering Pfizer COVID-19 vaccinations to youth ages 12-15, the county said on Twitter.

The FDA approved emergency use of the Pfizer vaccine in children ages 12 to 15 on Monday. Health experts hope the move helps curb the spread of COVID-19 in young people and local school officials hope it aids in the reopening process.

When the county gets the green light, staff is prepared to start vaccinations at county sites as early as Thursday morning.

Dr. John Bradley, medical director of the Division of Infectious Diseases at Rady Children’s Hospital in San Diego, joined FOX 5 Tuesday to explain why vaccinations for the age group are necessary.

“There’s a really good reason to try and immunize them and that has to do with both herd immunity,” he said. “We want vaccination levels in the community up so that coronavirus stops spreading, and we know if the masks come off, it will start to spread because there’s so many susceptible people.”

Dr. Bradley said there are 165,000 12 to 15 year olds in San Diego County. He said if all get vaccinated, the virus won’t spread nearly as effectively.

“And as you know, you can have asymptomatic infection in these kids, which is more common than adults. So if all the kids are immunized, we’re not spreading virus without even knowing it,” he said.

FOX 5 asked Dr. Bradley what he would tell parents who are concerned about possible side effects. He said there’s a big difference when it comes to vaccinating children younger than 12 and adolescents 12-15 years old.

“For most drugs and vaccines now, the FDA is including 12 to 15 year olds in the adult trials because physiologically they are very similar. And that’s what we saw with this Pfizer coronavirus vaccine, that the 12 to 15 year olds were an addendum to the original authorization.”

Dr. Bradley said studies involved 2,000 kids in the age group that were fully analyzed and tracked to show the vaccine is safe. He said for each age group under 12, it’s “a whole different ballgame.” He estimates vaccines for those children won’t be available until the end of the year or next year.

The final question FOX 5 asked Dr. Bradley was if he considers the vaccine safe given all of his experience and knowledge in the field. He said yes and pointed to data from the millions of people who have gotten the Pfizer vaccine.

“There’s been no vaccine where the FDA has had so much information so close to the immunization of populations in history,” he said. “And the FDA and the CDC are tracking that very carefully and there’s now virtually complete 6 months data from the original Pfizer studies.”

“Everyone who has been immunized can report any side effects and those are all being tracked and are recorded from out of the CDC and there was no safety problem. So after tens of millions of doses of vaccine, I think the people that were worried when the vaccines were first authorized in December, people who were worried there might be something, I don’t think they need to worry anymore.”

Dr. Bradley said Pfizer has not seen any problems with its vaccine like the rare side effect reported by some Johnson & Johnson recipients.