Doctors say the news is promising.
"Children 5-11 years old produce significant antibody response against COVID-19 with the dose scheduled as provided in this trial," said Dr. David Cornfield, Head of Pediatric Pulmonary Medicine at Lucile Packard Children's Hospital at Stanford.
RELATED: Pfizer says COVID vaccine safe, effective for kids ages 5 to 11
Bay Area trial participants are thrilled.
"It's so exciting," said Castro Valley resident, Renee Chavez, whose kids are part of a Pfizer trial at Stanford.
Renee is an ICU nurse at Lucile Packard Children's Hospital at Stanford.
"Knowing what COVID can do to kids, knowing we started seeing more pediatric cases. We wanted to do what we could to keep our kids safe to keep the kids in our community safe."
VIDEO: Doctors explain why smaller vaccine dose works for young kids
Dad, Miguel Chavez, says the benefits of enrolling his kids in the two-year Stanford trial outweighed any potential risk. "It's way worse to get COVID."
Nico, 9, and Sofia, 6, received their first in injection in June and their second in July.
Sofia Chavez: "It hurt my arm like a lot. Same thing with the other shot, except it was less."
Kate Larsen: "What do you think about being part of a vaccine trial? Do you feel brave?"
Sofia Chavez: "I feel good. I feel proud that I got into it."
Nico Chavez: "I immediately wanted to do it so I can have more time with my friends without masks, without COVID stopping me from doing that."
Kate Larsen: "After the second shot, did you feel sick? Flu-like at all?
Nico Chavez: "I felt chills, but I didn't really get sick."
The trial is still blinded, so the family doesn't know if Nico and Sofia got a placebo or the real Pfizer vaccine, but Renee says they both had low grade fevers after the shots.
"We don't have all the data in front of us. But for those of us who are doing the trials, I can tell you that the families and the kids are just doing really well. We just haven't heard of any major issues," said Stanford pediatric infectious disease doctor, Yvonne Maldonado.
VIDEO: Bay Area counties prepare to vaccinate kids 5-11 years old ahead of Pfizer's expected authorization
Maldonado says she's incredibly optimistic about the vaccine for younger children, which is a third of the dose of the adult and teen vaccine.
"This dose seems to provide great antibody responses. Some people have even talked about whether there should be efforts to look at the lower doses in adults too."
Dr. Cornfield says the robust antibody response is fascinating.
"They hit the 'Goldilocks zone' so-to-speak, where it wasn't too much and it wasn't too little. It was right at the correct spot," said Dr. Cornfield.
The 2,268 children who were part of the trial received two doses 21 days apart. Pfizer decreased the dose amount for this group, giving children a 10-microgram dose. Normally those 12-years-old and older get a 30-microgram dose. Even with this change, Pfizer says the response was strong.
RELATED: Booster shots: FDA advisory panel rejects widespread Pfizer jabs in blow to Biden's plan
Pfizer is planning to submit data to the FDA by the end of this month with hopes for a green light to start vaccinating kids 5 to 11 years old before Halloween.
"It is often the case that the immune response of children is more robust. It's more energetic, more powerful, if you will, than that of older people. Therefore, dosing the vaccine down a bit allowed for these kids to get efficacy from an antibody perspective, but also minimize any of the untoward effects of the vaccine. Any inflammation, any discomfort, any fever," said Dr. Cornfield.
This is a highly anticipatedannouncement,as we are seeing children go back to in-person classes.
According to theAmerican Academy of Pediatrics, COVID cases among children have increased about 240 percent in the U.S. since July.
VIDEO: Marin Co. prepares to vaccinate students ages 5-11 pending FDA approval
Today, San Francisco parent Melody De Leon said Pfizer's data gives her hope as her two daughters, 11-year-old Sophia and 6-year-old Emma, go back to school.
"Now that there is a vaccine there is a little relief," said Melody.
Ironically, Monday, Emma had to stay home because she woke up with a fever.
"First thing that crossed my mind because she has a fever and was vomiting is, 'Oh my God. Is it COVID?,'" said Melody.
VACCINE TRACKER: Here's how CA is doing, when you can get a coronavirus vaccine
Monday, Pfizer announced they will submit this data before the start of the winter season.
Melody says she will need that time to decide if she's comfortable with her daughters getting vaccinated. Even though Sophia says she's ready.
"You go places you never know if they have it, so I want to get vaccinated, so I don't get sick," said Sophia De Leon.
Once Pfizer's data is submitted, FDA officials believe the agency could authorize a vaccine for children 5-11 years old in a matter of weeks.
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