As with its adult vaccine, Pfizer/BioNTech was the first to cross the finish line and offer a Food and Drug Administration-authorized COVID-19 vaccine to children ages 5 through 11.
Here, we describe how it’s different from its grown-up cousin and what experts are saying about who should get it.
Quick Summary
Vaccine name: BNT162b2
Design type: mRNA
Dose number: Originally, 2 doses of 10 micrograms of modified mRNA, 21 days apart with a third primary dose recommended for certain immunocompromised children. Booster doses were later available. But as of September 2023, all doses are with an updated 2023-2024 vaccine, and only one dose of that vaccine is needed for primary vaccination.
Population: Children 5 through 11 years of age
Effectiveness: For the original shots, preliminary 90.7% efficacy in preventing symptomatic COVID-19 a week after receipt of the second dose and a comparable immune response to vaccinated young adults 16 through 25 years of age.
Safety: No serious safety concerns reported, although some rare allergic reactions and rare instances of myocarditis, or inflammation of the heart, are expected. The most common side effects, some of which are less frequent and more mild than in people 12 and up, include temporary injection-site pain, redness or swelling; fatigue; headache; and muscle pain.
Timeline: First doses were administered on Nov. 3, 2021.
Storage considerations: Vials are shipped under ultracold freezer temperatures of -130ºF to -76ºF but can be thawed and stored undiluted in a refrigerator for up to 10 weeks.
After months of waiting, the parents and legal guardians of 28 million American elementary school children now have access to a kid-sized version of Pfizer/BioNTech’s COVID-19 mRNA vaccine for their children.
The vaccine contains a third as much mRNA — 10 micrograms instead of 30 — but it is otherwise virtually identical to the adult version.
The FDA granted the pediatric vaccine an emergency use authorization, or EUA, on Oct. 29, 2021, after concluding that based on the collective evidence at this time, the known and potential benefits of the vaccine in kids 5 through 11 years old outweigh the known and potential risks. An independent panel of experts advising the agency came to the same determination in a 17-to-0 vote, with one abstention.
The 4,600-child clinical trial, which found the pediatric vaccine to be highly effective in preventing symptomatic COVID-19, did not identify any serious safety concerns. The adult COVID-19 mRNA vaccines, however, are known to very rarely cause inflammation of the heart muscle (myocarditis) or of the surrounding lining (pericarditis), particularly in young men. Myocarditis was therefore the primary risk considered in the evaluation.
An outside group of experts advising the Centers for Disease Control and Prevention then recommended the vaccine for children 5 through 11 on Nov. 2, 2021, in a unanimous 14-to-0 vote. The agency endorsed the recommendation the same day, enabling children to be immunized.
In January 2021, the FDA authorized a third primary dose of the original vaccine in certain immunocompromised kids, given 28 days or more after the second shot.
In May 2022, the agency authorized a booster for all children 5 to 11 years old, five months or more after a previous dose. This is a third shot for healthy children and a fourth dose for immunocompromised kids. The decision was based on safety data from about 400 children who received a booster in a trial and immune response data from a subset of those kids, which demonstrated an increase in antibody levels a month after boosting compared with before the booster.
On June 17, 2022, the FDA authorized an even lower 3 microgram dose of Pfizer/BioNTech’s COVID-19 vaccine for children 6 months through 4 years of age. For more on that vaccine, see “A Guide to COVID-19 Vaccines for the Youngest Kids.”
On Oct. 12, 2022, the FDA authorized — and the CDC endorsed — the first omicron-updated boosters for kids, given at least two months since the last dose. Those vaccines were bivalent, meaning that half of the mRNA in these shots targeted the BA.4 and BA.5 omicron variants, while the other half targeted the original virus. On April 18, 2023, the FDA ended the use of the original mRNA vaccines for both children and adults.
On Sept. 11, 2023, the FDA authorized newly updated vaccine doses for kids that target the omicron variant XBB.1.5 for the 2023-2024 season. These have replaced the earlier bivalent doses. For more on the updated vaccines, see “Q&A on the Updated COVID-19 Vaccines.”
Under the current rules, all 5- to 11-year-olds are eligible to receive a single dose of either the Pfizer/BioNTech or Moderna 2023-2024 updated shots, given at least two months after any earlier COVID-19 vaccines.
Pfizer/BioNTech 5-11 years Q&A
How is the children’s vaccine different from the adult version?
The biggest difference between the two vaccines is the amount of messenger RNA, or mRNA, in each shot. The mRNA provides the instructions to cells to make the spike protein of SARS-CoV-2, the coronavirus that causes COVID-19, thereby triggering the body to mount a protective immune response against the virus.
The lower 10-microgram dose was selected in a phase 1 dose-ranging trial, in which several doses were tested sequentially in a small group of children, with the kids being monitored for side effects and their immune responses evaluated by measuring how many coronavirus-specific neutralizing antibodies they produced.
Because the lowest dose of 10 micrograms provided a similar immune response to a 20 microgram dose but was accompanied by fewer side effects, it was chosen to be tested in the subsequent phase 2/3 clinical trial.
Another initial difference between the two vaccine formulations was in the buffer, or solution that helps the vaccine maintain proper pH. Until the end of 2021, the adult vaccine used phosphate-buffered saline, or PBS. But Pfizer switched to using another buffer known as Tris, or tromethamine, in the kids’ version because it increases the stability of the vaccine and allows the vials to be stored at warmer temperatures for a longer period of time. Now, both the adult and children’s shots use Tris.
Both buffers are common in medical products, including other vaccines for children, and have been shown to be safe.
Nevertheless, the change has led some people online to falsely suggest that the children’s shot is either not safe or indicative of a problem with the vaccines.
Pfizer told FactCheck.org that the modification does not change manufacturing and that the adult formulation of its vaccine will also soon use Tris for the same stability improvement.
“The manufacturing processes involved in producing the pediatric doses remain unchanged from the adult and adolescent doses. There are also no changes in raw materials, mRNA, lipids or suppliers in the manufacturing of the drug substance and lipid nanoparticles,” the company said in an email (emphasis is Pfizer’s). “To enable extended storage time an alternative buffer is being leveraged, known as a ‘tris buffer’. Simply put, this allows the mRNA to resist being degraded for a longer period of time before administration — meaning the pediatric vaccine can be stored for 2-8°C in commonly available refrigerators for up to 10 weeks. This buffer will also be used in the updated adult/adolescent 30mcg doses in due course, helping to ensure simplified handling of the vaccine across age groups.”
The pediatric trials did not use the Tris formulation, but the FDA has said lab tests were done to ensure the change did not alter the vaccine’s safety or effectiveness, and that the switch is “not considered clinically significant.”
Dr. H. Cody Meissner, then-chief of pediatric infectious disease at Tufts Children’s Hospital, and a member of the committee advising the FDA, also told us that he didn’t think the change in buffers would “make much of a difference at all.”
How effective is the vaccine?
Preliminary data from a randomized, placebo-controlled trial showed that at least a week following the second dose, two doses of the original vaccine were 90.7% effective in preventing symptomatic COVID-19 in children 5 through 11 years of age. This figure means that a vaccinated child is about 90% less likely to fall ill than a similar unvaccinated child.
In the study, which has enrolled about 4,700 kids in the U.S., Finland, Poland and Spain, two children received the vaccine for every child receiving a saline placebo. As of Oct. 8, 2021, three COVID-19 cases occurred among 1,305 vaccinated children compared with 16 in 663 placebo recipients, which is how the 90.7% number is derived.
Symptomatic disease was defined as having at least one symptom and a positive test for SARS-CoV-2 infection. Most of the cases occurred over the summer of 2021, when the delta variant was widespread. No cases in either group were considered severe, and there were no deaths.
These data, however, are considered supplemental, and were not the primary way regulators assessed effectiveness. Instead, the plan was to take a so-called immunobridging approach, in which a random selection of children in the trial are evaluated for their immune response to the vaccine, which is then compared to that of young adults receiving the adult dose, for whom a clinical trial previously demonstrated efficacy. If the immune response is similar, or what is termed “non-inferior,” then it is inferred that the vaccine works in younger children.
In this case, scientists looked at the average SARS-CoV-2 neutralizing antibody titers one month after the second dose in 264 kids 5 through 11 years old and compared it to the average observed in 253 vaccinated 16- to 25-year-olds. Pfizer’s study found the averages to be the same (see page 22). Additionally, the same proportion of individuals in each age group — 99.2% — produced antibodies following vaccination.
It is not known how effective the vaccine is at preventing children from becoming infected or spreading the coronavirus, as that was not explicitly studied in the clinical trial. However, if the vaccine performs similarly in children as in adults, the pediatric vaccine should temporarily reduce — although not eliminate — both infection and transmission.
How safe is the vaccine?
Safety was evaluated in around 3,100 children who received the pediatric Pfizer/BioNTech vaccine, and no serious concerns were identified. About half of these children were followed for at least two months after their second dose, while the other half had a median of a little more than two weeks of safety data.
Similar to the adult vaccine, the most common side effects in children were pain, redness or swelling at the injection site, as well as fatigue, headache and muscle pain. However, these side effects were generally more mild and less frequent in children than in those receiving the adult dose. Most of these reactions were mild and resolved within one or two days and often were worse after the second dose.
Less than 1% of children developed lymphadenopathy, or swelling of the lymph nodes, and a similar number experienced a rash. The only serious adverse events observed in children, such as a broken arm, were deemed by the FDA to be unrelated to vaccination.
No kids in the trial developed dangerous allergic reactions or myocarditis or pericarditis. However, because those conditions have on rare occasions occurred in people following vaccination with Pfizer/BioNTech’s adult vaccine, regulators do expect them once the pediatric vaccine is rolled out to millions of children.
In a positive sign, vaccine-related myocarditis appears to be less common in 12- to 15-year-olds than in 16- to 29-year-olds, suggesting the risk would be even lower in younger children, especially given the lower amount of mRNA used in the vaccine. Traditional myocarditis is also less common in younger children, further lending credence to that hypothesis.
In its benefit-risk assessment, the FDA modeled a series of scenarios assuming the myocarditis rate in vaccinated kids 5 through 11 years old is the same as in 12- to 15-year-olds. The agency then incorporated different variables, such as different levels of protection afforded by the vaccine, along with different levels of coronavirus circulation and COVID-19 death rates in children. According to the model, the vaccine prevents more bad outcomes from COVID-19 than it causes in all scenarios, except for the one in which viral transmission falls to its low point in June 2021. In that case, there are more hospitalizations due to vaccine-related myocarditis than those prevented from COVID-19, but because vaccine-related myocarditis is usually less serious than typical myocarditis, the FDA said the overall benefits still might outweigh the risks.
The FDA and CDC will be monitoring for any serious side effects of this vaccine in children, but are keeping an especially close eye on myocarditis.
As of early March 2023, 23 verified reports of myocarditis had been observed in children 5 through 11 after more than 23.4 million doses administered, indicating the risk of vaccine-associated myocarditis is very low for children and well below that of teenagers and young adults.
A review of vaccine safety by the CDC advisory committee in May 2022 similarly found that myocarditis following vaccination is rare for kids 5 through 11, with a “slightly elevated” reporting rate among males after the second dose.
Although uptake was low, myocarditis wasn’t flagged by the CDC’s Vaccine Safety Datalink program as a potential side effect of the bivalent boosters for any age group.
Do experts recommend that all children receive this vaccine?
Editor’s note: This section pertained to the original vaccines. The CDC recommends that all kids get the updated 2023-2024 vaccine as well. For more on what experts say about those shots, see “Q&A on the Updated COVID-19 Vaccines.”
Many experts and the CDC and American Academy of Pediatrics recommend that all children 5 years of age and older get vaccinated, unless they have a contraindication, such as an allergy to a vaccine ingredient.
While infection with the coronavirus is typically mild or without symptoms in young children, some kids have been hospitalized and have died.
According to the CDC, since the pandemic began, there have been at least 1.9 million cases of COVID-19 in U.S. kids 5 to 11 years old, including 8,300 hospitalizations and 94 deaths. The death toll, while low, is enough to have made COVID-19 one of the top 10 causes of death in 2019 among children in this age group.
There also have been at least 2,316 cases of multisystem inflammatory syndrome in children, or MIS-C, an inflammatory condition following infection with SARS-CoV-2 that is fatal 1% to 2% of the time and requires intensive care in 60% to 70% of cases. MIS-C is rare but is most common in the 5-to-11 age group.
Additionally, a U.K. study found 7% to 8% of children experience symptoms more than 12 weeks after diagnosis, even if the initial infection is mild. This suggests children do get “long COVID,” although to a lesser degree than adults.
On the other side is the potential risk of myocarditis, which most experts consider to be a real, albeit rare, side effect of the Pfizer/BioNTech vaccine.
“In my mind, it really is not a close clinical call,” said Dr. Ashish Jha, dean of the Brown University School of Public Health, in a Nov. 3, 2021 press call with reporters. “I think every child in America 5 to 11 should get vaccinated.”
Dr. Paul A. Offit, a vaccine expert and pediatrician at the Children’s Hospital of Philadelphia who is also on the FDA’s advisory committee, agrees.
“It should be all children who are 5 to 11,” he said in a phone interview.
At the FDA advisory committee meeting, however, some members expressed reservations about rolling out the vaccine to all children and especially of mandating it, when the risk of COVID-19 is so low to young children and the myocarditis risk of the vaccine is not yet fully known.
Tuft’s Meissner, for example, said he was concerned about states issuing mandates for children to be vaccinated to attend school. “I think that would be an error at this time, until we get more information about the safety,” he said.
Dr. Michael Kurilla, the director of the division of clinical innovation at the National Institutes of Health’s National Center for Advancing Translational Sciences — and the sole person not to back the vaccine with a “yes” vote — was not convinced that all children would necessarily benefit all that much from the vaccine, especially when CDC data suggest around 40% of children may already have been infected.
“While there are clearly high-risk groups within the 5 – 11 age group for which this vaccine would significantly reduce serious disease, I do not expect protection from infection to last more than a few months and this may negatively impact public perception of vaccines,” he said in a statement to FactCheck.org explaining his abstention vote. “Taken together, I don’t see the need for ‘emergency use’ of this vaccine across the entire age group and would have preferred a more nuanced approach.”
Offit, however, disagrees, noting that while around two-thirds of children who were hospitalized with COVID-19 had one or more underlying risk factors, that still leaves a good chunk who were not.
“One-third of those children who were hospitalized were perfectly healthy prior to that,” he said. “So I don’t think you can reasonably kind of layer the recommendation to include just those with certain comorbidities.”
“It should be striking to parents that this virus in terms of mortality is in the top 10 causes of death,” he said. “A choice not to get a vaccine is not a risk-free choice. It’s a choice to take a different risk.”
Other committee members were ultimately swayed by the data, but recognized the challenges of the remaining uncertainty.
Dr. Patrick Moore of the University of Pittsburgh School of Medicine called the decision a “hard … but a clear one,” and Dr. Michael Nelson of the University of Virginia School of Medicine emphasized the need for parents to have conversations with their pediatricians.
“Providing choice to a fully risk-informed public using a shared decision-making model with their trusted providers, to me, is a pretty reasonable way ahead,” he said, adding that there were millions of high-risk children and family members who needed the vaccine.
In a phone interview, Meissner said he voted “yes” because he wanted the vaccine to be made available to anyone who wanted it, but also said that it should be made clear to parents that the myocarditis risk is not fully known and that it’s possible the vaccine could cause more hospitalizations than it prevents.
Although most of the vaccine-related myocarditis cases appear mild and self-resolving in adults, he noted that some patients still show abnormalities on MRI scans, and it’s not yet known what that means.
“Based on the facts that we have now, I think many parents may elect to wait and see what the experience turns out to be with other children in this age group,” he said, “and I think that’s a very reasonable approach.”
If there is a risk that outweighs the benefits, Meissner said, that should become clear within several months.
“I think that the United States has the best safety monitoring system in the world,” he said. “That’s why I would feel comfortable waiting a few months, until the vaccine safety signal is clear and there aren’t problems. And then, I think, it would be reasonable to go ahead with a strong endorsement for administering the vaccine.”
Safety monitoring data as of early March 2023 suggest that the risk of vaccine-related myocarditis for children 5 through 11 is indeed very low, and as expected, lower than for teens and young adults.
When and where can I get my child vaccinated?
The 2023-2024 vaccines are no longer provided by the federal government for free, but private insurance companies, Medicare and Medicaid, and some CDC programs will cover them.
The Vaccines for Children Program provides free vaccines for kids who are either Medicaid-eligible, uninsured, underinsured, or American Indian or Alaska Native. See the CDC’s website for more information on where to get vaccines through the VFC.
Vaccines.gov provides information on where to get the vaccines. In addition to pharmacies, the updated vaccines may be available at doctors’ offices.
Should nearly 12-year-olds wait until their birthday to get vaccinated so they can receive the adult vaccine?
You should consult with your child’s pediatrician, but waiting to be vaccinated could leave a preteen susceptible to COVID-19, as Dr. Sallie Permar, the chair of pediatrics at Weill Cornell Medicine, told the Atlantic and multiple other experts told the New York Times.
There also may not even be any advantage — and your child might have an easier time with the temporary side effects with the lower dose.
“I think I would actually prefer to get them the lower dose,” Permar said. “Pediatric immune systems are more well set up to respond to low doses. They may even achieve a better response. We’ve been studying this in the HIV-vaccine world for several years now. A lower dose in a young age group can achieve a better immune response than even a higher dose.”
While these age cutoffs are arbitrary on one level, there is a solid basis for giving younger people a lower vaccine dose than older people — and it’s not because of a person’s size. The rationale has to do with the development of an individual’s immune system.
Younger people — and especially younger teens and kids — tend to have more energetic responses. Vaccine doses therefore can be lower for them, and this also helps keep the side effects more manageable. Conversely, for older people, sometimes higher-dose vaccines are needed to ensure a robust response.
There is no need to worry that your large-for-his-age 10-year-old would be less protected or need an adult dose because of his larger physical size. Unlike medications, which often need to be prescribed by weight because a compound will only work at a certain concentration, vaccines are not based on weight and do not need to be sized-up for larger bodies.
The trial data did not show differences in neutralizing antibody levels in 9- to 11-year-old children versus 5- to 6-year-old kids. Of the three cases of mild COVID-19 in the kids who were vaccinated, two were in 10-year-olds and one was in an 11-year-old. It is unclear whether that is indicative of anything, though, as this could reflect the higher exposure to the virus among older children, as older kids in the placebo group were also more likely to fall ill.
That being said, it may depend on exactly how close your 11-year-old is to turning 12. With other vaccines, there is often a four-day grace period that allows providers to inoculate children four days earlier than recommended — and the CDC has said that rule will also apply here.
Will the COVID-19 vaccine be required for elementary school students?
It’s possible that eventually COVID-19 vaccination will become a prerequisite for enrollment in some public schools, much the way other vaccines for childhood diseases are required.
But experts are skeptical that mandates would happen very soon — and many are opposed to them for children, at least for now.
In the FDA advisory committee’s discussion, multiple members, including Tuft’s Meissner, were particularly concerned about a “yes” vote being misinterpreted as supportive of a mandate at this time, which was not their position.
In an effort to reassure the committee, Dr. Peter Marks, director of the Center for Biologics Evaluation and Research at the FDA, pointed out that mandates are less likely when a vaccine has only emergency use authorization, and several governors have specifically stated they would not implement a mandate without full approval.
Similarly, Jha noted that COVID-19 vaccine mandates for adults did not arrive on the scene for about six months — and that he suspects any mandates for kids would also come later.
“Back in December [2020], we did not have vaccine mandates immediately. We let people choose to get vaccinated or not,” he said. “That’s how I envision what should be happening with children right now — is let kids get vaccinated, give parents time to have those conversations with their pediatricians, let people get comfortable with this.”
Jha said that while he’s generally supportive of vaccine mandates for other people, he did not think that they are appropriate right now for 5- to 11-year-old children.
According to the National Academy for State Health Policy, as of August 2023, no states require COVID-19 vaccination for students in K-12 schools.
Editor’s note: SciCheck’s COVID-19/Vaccination Project is made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. The goal of the project is to increase exposure to accurate information about COVID-19 and vaccines, while decreasing the impact of misinformation.