Pfizer said Thursday it's asked the US Food and Drug Administration to authorize use of a low-dose version of its Covid-19 vaccine for children 5 to 11.
It would be the first Covid-19 vaccine for younger children. The Pfizer/BioNTech vaccine is approved for people age 16 and older and has emergency use authorization for children 12-15.
What does that means for children and their parents? Here are some questions and answers:
When will the vaccine be authorized?
In theory, it could be authorized for children by early November.
Two different federal agencies will consider whether kids should get these new vaccines.
The FDA will examine the data submitted by Pfizer and BioNTech and has made it clear it will do so carefully. The FDA is aware of the sensitivities people have about vaccinating children. "We know from our vast experience with other pediatric vaccines that children are not small adults, and we will conduct a comprehensive evaluation of clinical trial data submitted in support of the safety and effectiveness of the vaccine used in a younger pediatric population, which may need a different dosage or formulation from that used in an older pediatric population or adults," acting FDA Commissioner Dr. Janet Woodcock says.
The FDA has already scheduled a meeting of its independent advisers, the Vaccines and Related Biological Products Advisory Committee or VRBPAC, for October 26 to discuss the data. VRBPAC, which includes several pediatricians, will listen to what both Pfizer and the FDA have to say about what studies show and will also hear public input.
The FDA could act quickly after the VRBPAC meeting -- in hours, even -- and then vaccine advisers to the US Centers for Disease Control and Prevention will meet. The Advisory Committee on Immunization Practices is made up of different experts.
ACIP has scheduled a meeting for Tuesday and Wednesday November 2-3 to discuss the question. The CDC Director, Dr. Rochelle Walensky, will then decide whether kids should get the vaccine based on this input.
Does that mean kids could be protected by Halloween?
Just as with adults, Pfizer is testing and proposing a two-dose series for kids. So that would mean two doses of vaccine given three weeks apart. And as with adults, immunity isn't immediate, even after the second dose. People have been considered fully vaccinated two weeks after the second dose and the same will go for kids.
So at the very earliest, children would be advised to continue taking precautions for five weeks after they get the first dose of vaccine. That means wearing masks, keeping a physical distance from others and avoiding crowded indoor spaces when possible.
As for boosters, it's far too soon to ask about them. It took several months of gathering real-world data before Pfizer asked FDA to authorize boosters in adults.
Will kids get the same dose as adults?
No. Pfizer has been testing a 1/3 dose in children 11 and under. But indications are that this smaller dose will protect kids just as well as a larger dose protects teens and adults -- even if a particular 10- or 11-year-old is large for his or her age.
Vaccine makers test varying doses when they are doing clinical trials to try to get the best immune response possible from the lowest dose possible. This can reduce side effects and stretch supply.
Tests in children showed a strong response to a 10-microgram dose in the clinical trials, says Dr. Robert Frenck, who heads up vaccine trials at Cincinnati Children's Hospital and who has been testing Covid-19 vaccines in children there.
"We looked at 10 micrograms, 20 micrograms and 30 micrograms in adults," Frenck told reporters last month. "We found in 18- to 55-year-olds a 10-microgram dose gives a very good immune response," he added. "But the 65 and above, they did not respond as well to the lower doses and so that's why we chose that 30-microgram dose across the adult age range from 18 to above."
A bigger initial dose did not seem to improve immunity, so even older children won't miss out if they get the smaller dose.
"My guess is that if we gave a 12-year-old a 10-microgram dose that they would still have a similar immune response as a 30-microgram dose, but we don't have the data for that," Frenck said.
For the youngest children, children under 5, doctors are testing a 3-microgram dose of vaccine.
What are the side-effects?
Frenck says so far, the Pfizer vaccine appears very safe in younger children. "What we found is that the side effects in the children really mirrored exactly what we saw in adults," he said.
For the most part, that means a sore arm at the vaccination site. Some people feel headaches or tiredness. In the trials, about 10% of kids had fever or chills after the vaccine -- similar to side effects from other types of vaccine. They last a day or two at the most, Frenck said.
The CDC recommends a cold compress at the site or a dose of non-aspirin pain reliever if children are bothered by the side-effects.
Many parents may be worried about reports of a rare heart inflammation called myocarditis, which has been seen with both Moderna's and Pfizer's vaccines.
"And so the myocarditis -- which means swelling of the muscles of the heart -- we have seen that as a rare side effect has been associated with it looks like the second dose of either the Moderna or Pfizer vaccine," Frenck told reporters.
"Rare meaning in the likelihood of a few per 100,000, so it's still like a 99.999% chance that this won't happen. It's been almost all in teenage boys, and it's been mild, been treated with Motrin (ibuprofen), and they've gotten better."
How many kids has this vaccine been tested in?
Pfizer has been running several clinical trials at hospitals across the country and more details will be released when the FDA publishes what Pfizer has submitted -- likely in the coming days.
Last month, Pfizer released details of a Phase 2/3 trial involving 2,268 children 5-11 years old.
Unlike trials involving tens of thousands of adults that gave placebo or dummy doses to some and then looked to see how many people became infected, Pfizer used what are called immunobridging studies among the kids.
These studies -- long accepted as a way to test a vaccine approved or authorized for adults in children—uses the immune system response generated by the vaccine as a proxy for protection. If kids' bodies generate the same level of antibodies as adults do after vaccination, it's assumed the children are equally protected.
Pfizer said the antibody levels seen in kids who got the 10 microgram doses compared well with older people who received the larger doses, demonstrating a "strong immune response in this cohort of children one month after the second dose."
Where will kids get vaccinated?
The same places they get flu vaccines -- their pediatricians' offices, at local pharmacies and perhaps at some schools.
"This is the pediatrician's wheelhouse," Dr. David Kimberlin, who helps lead the pediatric infectious diseases division at the University of Alabama at Birmingham, told CNN Thursday.
"We're trying to get pediatricians enrolled and that's a major strategy," Claire Hannan, executive director of the Association of Immunization Managers, told CNN's Jacqueline Howard.
One potential pinch point is the smaller dose of vaccine, which means the younger children cannot be given doses in stock for adults and teens.
The kids' vaccine is expected to be shipped in packages of 100 doses, which is much smaller than the packages of 1,170 doses used for the adult vaccines.
"The fact that they're moving to smaller packaging and smaller shipping amounts is really great news," Hannan said. That will be easier for doctors' offices to manage.
The CDC notes that government websites help people find places to get vaccinated.
"Search vaccines.gov, text your ZIP code to 438829, or call 1-800-232-0233 to find locations near you," the CDC advises.
"I think the real key is to get enough parents interested in having their children vaccinated," Kimberlin said.
Dr. Peter Hotez, a pediatrician and vaccine expert at the Baylor College of Medicine in Houston, noted a big divide exists in the US. "Only 33% of the 12-17-year- olds were given the Covid-19 vaccine here in the South," Hotez told CNN's Ana Cabrera Thursday.
"So once again you have this geographic divide where parents are holding back on vaccinating their adolescents -- and I have to believe they will probably hold back on vaccinating the younger kids as well," Hotez said.
"We may be looking at very low up take of this pediatric vaccine in the South and also in the mountain West, and that's going to be a problem that's going to slow us down."
What about other vaccines?
Kids can get the Covid-19 vaccine alongside flu vaccines and other immunizations.
"It is safe and effective to get both vaccines at the same time," CDC Director Dr. Rochelle Walensky said Wednesday at the White House Covid-19 briefing.
"You can get any vaccines together that's necessary," Frenck said.
"The only restrictions is if we have live viral vaccines, like with chickenpox and measles, if they don't get those on the same day we'd like to space them at least a month apart. But for the Covid vaccines, they can be given with the flu vaccine," he added.
"There's no need to space -- our immune system can handle all the vaccines at the same time."
If possible, different vaccines should go into different arms and legs if they're given on the same day, CDC vaccine officials told clinicians during a call Thursday.
"Co-administration of influenza and other Covid-19 vaccines is encouraged," Dr. David Shay, a medical officer with the CDC's National Center for Immunization and Respiratory Diseases, said in a CDC Clinician Outreach and Communication Activity call.
"The recommendation for this year is that Covid-19 vaccines may be administered without regard to the timing of other vaccines, and that would include simultaneous administration of Covid-19 vaccine and other vaccines on the same day," he said, adding that the CDC is currently monitoring the effects of co-administration on the Covid-19 vaccine.
This story has been updated to reflect the newly scheduled meeting of CDC's ACIP in November.
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