Pfizer / BioNTech’s Covid-19 vaccine that has just been cleared for young children will still require two injections on the same schedule as the vaccine for adolescents and adults – but the doses will be one-third the size.
For ages 5 to 11, the US Food and Drug Administration has authorized a dose of 10 micrograms; the dose used for people 12 years of age and older is 30 micrograms. Moderna recently published the first results of a two-dose Covid-19 vaccine for children aged 6 to 11, half the size of the company’s vaccine for adults.
So why is there a difference? And what should parents of 11-year-olds do, especially if the child is approaching 12?
Find the right dosage
One of the goals of all-age vaccine trials is to find the lowest level of antigen – the part that triggers an immune response – to maximize protection without side effects.
“We believe that we have optimized the immune response and minimized the reactions,” Pfizer senior vice president Dr. William Gruber told FDA vaccine advisers of the company’s Covid-19 vaccine on Tuesday for young children.
It is not about the size of the child. Rather, it is that small children are still developing and the immune system weakens with age.
“Children actually tend to have very robust immune responses,” said Dr. Kari Simonsen, who led the Pfizer vaccine trial at Children’s Hospital & Medical Center in Omaha, Nebraska. “In some cases, they can actually create strong responses to smaller amounts of vaccine antigen.”
For some vaccines, the doses for adults and children may be the same, but in other cases, such as with hepatitis A vaccine, adults receive a higher dose than children.
“As we like to say in pediatrics: Children are not little adults. Children are children,” said Dr. James Versalovic, acting chief pediatrician of Texas Children’s Hospital. “Their bodies develop and will respond differently, and we need to treat them differently.”
It was a consideration that Pfizer tested vaccines in young children.
“We took a step back after we did the teens, and we looked at the dosage because we thought we could maybe use a lower dose and get the same immune response,” said Dr. Bob Frenck, director. from the Cincinnati Children’s Hospital Vaccine Research Center.
After the tests, “we got an immune response as good as the 30 microgram dose and there were fewer side effects.”
According to data from a Phase 2/3 trial submitted by Pfizer in September, the two-dose 10-microgram vaccine generated a “robust” antibody response in young children. In a document released last week, Pfizer said its vaccine was 90.7% safe and effective against symptomatic Covid-19 in children aged 5 to 11.
At higher doses tested in trials, the scientist found a few minor side effects, nothing serious. With the 10 microgram dose, the researchers found fewer problems with chills and fever than in the 16 to 25 age group tested.
The lower dose should also reduce the theoretical risk of myocarditis, the inflammation of the heart muscle that has been seen in a small number of people after receiving the Pfizer and Moderna vaccines. No cases of myocarditis were seen in the youngest children in the trial, but not enough children were tested to show whether they are also at risk. Scientists will be watching the cases closely.
“It reassures me that we are giving a lower dose,” said Dr. Paul Offit, a member of the FDA’s independent vaccine committee who heads the Vaccine Education Center at Children’s Hospital of Philadelphia.
Should a child almost 12 years old wait for a larger dose?
Some parents of 11-year-olds may wonder if they should wait for the higher dose, but Dr. Bernhard Wiedermann, an infectious disease specialist working on the Pfizer trial at Children’s National in Washington, DC, said parents shouldn’t wait until the child is 12.
“If I had a family member in this situation, I would just advise them to get the dose allowed for their current age,” Wiedermann said. “I think we still have a reasonable risk that cases will start to rise again in the next few months.”
Pfizer’s Gruber said dose levels for 12 to 15 year olds could be reduced at some point, but there is no data yet to support such a change. Previous research has shown that this age group had a higher antibody response with the 30 microgram dose.
“We are thinking of this as a potential option, especially as we come out of the pandemic period,” said Gruber, referring to considering a smaller dose. “The main focus at the moment is obviously to provide protection with a safe and effective vaccine.”
Wiedermann said doctors shouldn’t embrace the idea and use it now for 12 to 15 year olds.
“I told our suppliers that you should always stay within the lines when coloring,” said Wiedermann. “The immune response for this virus is very complex. A practitioner may think that he is giving a higher dose or a lower dose that he is helping a particular child, but if this has not been studied, do not don’t, because we really don’t know what the effects will be. Now is not the time to play with anything outside of what has been allowed. “
What happens next?
On Friday, the FDA cleared the Pfizer / BioNTech vaccine for emergency use in children aged 5 to 11.
Next, the CDC’s independent vaccine advisory committee will meet on November 2 and vote on whether to recommend its use.
Finally, CDC director Dr. Rochelle Walensky will decide whether to accept or modify the recommendation of the CDC committee. Once a recommendation is final, young children could start getting the vaccine immediately.
Some 28 million children are believed to be eligible for the Covid-19 vaccine, and plans are already underway to help them get it. Getting this group vaccinated could bring the country closer to the end of the pandemic, experts said.
“If we can create a situation where more of these children are not infected, we should be able to bring this pandemic down, which we really hope to do even as we face the cold and other concerns about if we could see a new wave, “Dr. Francis Collins, director of the National Institutes of Health, said on ABC’s Good Morning America show Tuesday.” We don’t want that, and it would be a step forward important for our country to truly be in a better place. “
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