(CNN)The US Food and Drug Administration gave emergency use authorization for booster doses of Pfizer/BioNTech's Covid-19 vaccine for children ages 12 to 15 Monday.
The agency also shaved four weeks off the waiting period for the booster after the administration of the second dose, from at least six months to at least five months for everyone 12 and older.
"The FDA expanded emergency use to a whole group of people, children aged 12 to 15, who were not previously eligible for boosters," said pediatrician and child development expert Dr. David Hill, former chair of the American Academy of Pediatrics Council on Communications and Media.
"Additionally, the FDA recommended boosters for some children ages 5 to 11 who are severely immunocompromised, meaning that particularly vulnerable children down to age 5 can now get the booster vaccine," said Hill, who is a co-host on the AAP's flagship podcast, "Pediatrics on Call."
CNN asked Hill questions that parents and caregivers will want answered as they wait for formal recommendation of boosters, expected later this week after the US Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices, or ACIP, meets Wednesday and a final go-ahead from CDC Director Dr. Rochelle Walensky.
This conversation has been edited and condensed for clarity.
CNN: You mentioned that children down to age 5 who are immunocompromised are also eligible for the booster. How is that defined?
Dr. David Hill: What they are giving us as an example is a child who's had a solid organ transplant, for example, like a kidney or liver transplant. But they are also saying children with equivalent degrees of immunocompromise -- for example, there are hereditary conditions that may lead to fairly severe degrees of immunocompromise. Those children are almost certainly already being seen by an immunologist or an infectious disease specialist.
If you are a parent who thinks that your child may qualify for the booster based on their immune status, check in with a doctor who is managing their condition and see what they say.
CNN: When will boosters for this age group be available?
Hill: That is a great question. What we know is that there is one more step: a meeting of the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices, called the ACIP. The CDC has said that they are anticipating a meeting later this week. Once the ACIP signs off on this, then implementation should occur very quickly.
There can be delays in terms of ordering and stocking the vaccine in various locations.
CNN: How will I know if the booster will be in stock in my area?
Hill: I know that the availability of vaccines continues to vary by location and demand. I have not seen specific reports on where shortages might exist. I do know that you can check in with local health care authorities or your health department to find the best place to get the booster administered.
CNN: What do I need to bring to the appointment?
Hill: Definitely bring your child's vaccine card. The booster needs to occur at least five months after the child's second dose of Pfizer or Moderna vaccine, so facilities will be looking for some evidence as to when that second dose was administered.
Many states now have a statewide vaccine registry. If the location where you got your booster participates in the statewide registry, there may actually be an electronic document that should be available throughout the state, so that's another source of confirmation.
And then there is your child's electronic health record, which track vaccines. The electronic health records sometimes have to be adjusted to accommodate the development of a new vaccine or a new vaccine schedule, and the vendors who program those records are usually very responsive, to make sure that the systems are ready when the CDC approves the booster.
CNN: How does this dose compare to the original vaccine doses and what are the side effects?
Hill: It should be the same. I haven't seen that there is any difference in the dose for the booster compared to the first two vaccines.
The common side effects from the booster remain the same as they are for the first two vaccines, so obviously there may be pain or redness or swelling at the injection site. Some people will experience fatigue or headaches, they may have muscle or joint pains, they may have chills.
One thing that seems a little bit more common with the booster dose is swollen lymph nodes in the armpit of the arm where the dose was given. Lymph nodes are our body's way of responding to infection or inflammation, so it's not unusual with any inflammatory response to see some lymph nodes swelling. But that seems to be a little more common with the booster dose.
The good news, in terms of side effects, is that none of the children studied so far have developed cardiomyopathy. That doesn't surprise us, because you probably need to get millions of shots before you think a single case of cardiomyopathy, and of course we haven't given millions of third vaccines in this age group yet. But it's very heartening that, of the people who have been studied, there has not been a single case.
CNN: Would you advise parents and caregivers to keep their child home from school the day after their booster shot?
Hill: I think most children will be able to go to school the following day. But if childcare is difficult for you, it would probably be good to have a backup plan in case your child were to feel too bad or to have a fever that would keep them out of school.
CNN: How long before that boost of immunity kicks in after the booster shot?
Hill: What we know so far from boosters in other age groups is that it looks like a significant boost in the immunity you already have occurs in the first seven