Pfizer’s and Moderna’s COVID-19 Vaccines OK’d for Youngest Kids

click to enlarge A 3-year-old gets a Pfizer COVID-19 vaccine last year in a clinical trial for children ages 6 months through 4 years. - STEVE FISCH/STANFORD MEDICINE
STEVE FISCH/STANFORD MEDICINE
A 3-year-old gets a Pfizer COVID-19 vaccine last year in a clinical trial for children ages 6 months through 4 years.

The littlest kids in the United States are done waiting for their own COVID-19 vaccine.

On June 18, an advisory committee to the U.S. Centers for Disease Control and Prevention unanimously recommended Moderna’s and Pfizer-BioNTech’s mRNA vaccines for babies, toddlers and preschoolers. CDC director Rochelle Walensky endorsed that recommendation hours later. The U.S. Food and Drug Administration had granted emergency use authorization of the vaccines on June 17, two days after the FDA’s advisory committee had voted unanimously in favor of the authorization.

The recommendation — a relief to many families of young children who’ve endured multiple COVID-19 surges, restricted outings and daycare disruptions — comes two and a half years after adults were first vaccinated against COVID-19 in December 2020 (SN: 12/18/20). This young age group consists of approximately 18.7 million children.

“This recommendation does fill a significant unmet need for a really ignored younger population,” said FDA committee member Michael Nelson, an allergist and immunologist at the University of Virginia School of Medicine in Charlottesville. He hopes every child in the United States “gets vaccinated in the near future.”

The first shots for the littlest kids could be available as early as June 21. According to plans released by the Biden administration, an initial 10 million doses for young children will come first, with millions more arriving in the following weeks. Families will be able to get the shots at pediatrician offices, community health centers, public health clinics, children’s hospitals and pharmacies, among other locations. The goal is that 85 percent of kids under 5 will be within 5 miles of a vaccination site.

The FDA and CDC advisory committee meetings were a reminder yet again that the youngest are not free of risk from COVID-19. Among children, those 0 to 4 years old have the highest number of deaths compared with those who are older: 485 kids ages 0 to 4 have died, topping the 366, 384 and 311 reported in the 5–11, 12–15 and 16–17 year age groups, respectively, according to the CDC’s COVID Data Tracker as of June 17.

From March 2020 through April 2022, COVID-19 was the fourth leading cause of death for children under 1 year old and the fifth leading cause for kids ages 1 through 4. COVID-19 is the only infectious disease among the top five. The burden of deaths from COVID-19 is similar to or greater than that of other pediatric vaccine-preventable diseases, said Sara Oliver, a medical officer with the CDC’s National Center for Immunizations and Respiratory Diseases, during a presentation at CDC’s advisory committee meeting.

The winter surge driven by the omicron variant of the coronavirus was especially hard on the littlest kids (SN: 3/1/22). For children under 5, there were 14.5 hospitalizations per 100,000 children in the United States during the peak of omicron, a rate five times as high as that seen during the delta variant’s peak, researchers reported in March in the Morbidity and Mortality Weekly Report.

Roughly 1 in 4 children under 5 hospitalized with COVID-19 end up in the intensive care unit, said pediatrician Evan Anderson of Emory University School of Medicine in Atlanta during a presentation at the FDA’s advisory committee meeting. “Having cared for many children that have been in the ICU on ventilators for COVID … and having cared for several children that have died of COVID, we need to be able to prevent COVID-19,” Anderson said.

The seriousness of the illness means that “prevention is really the way to go,” said FDA committee member and pediatric infectious disease specialist Hayley Gans of Stanford University School of Medicine. The COVID-19 vaccine is “a breakthrough that has allowed us to move through the pandemic … [with] less suffering and disease.”

The benefits of vaccination also extend to young children with a prior COVID-19 infection, Oliver said during the CDC’s advisory committee meeting. An estimated 71 percent of 6 month to 4-year-olds in the United States have evidence of a past bout of COVID-19 as of this spring. But the protection from infection-induced antibodies is not as robust as that from antibodies produced after COVID-19 vaccination, research has found. In children and adolescents, those vaccinated twice had higher levels of virus-blocking antibodies against different coronavirus variants, including omicron, than did those who only had a SARS-CoV-2 infection, researchers reported in May in Nature Communications.

Vaccination against COVID-19 even in those previously infected is still important to help protect against future infections and prevent severe disease, Oliver said.

At both advisory committee meetings, members reviewed immunity and safety data for Moderna’s and Pfizer’s shots for the youngest children. The two vaccines have different dosing and timelines. Moderna’s mRNA COVID-19 vaccine for kids 6 months through 5 years is a two-dose series, 25 micrograms per dose, given four weeks apart. (Adults get two 100 microgram doses for their initial two-dose series of shots.)

Pfizer’s option, for kids 6 months through 4 years, is a three-dose series with 3 micrograms per dose. The first two shots are given three weeks apart, followed by a third dose at least eight weeks later. (The initial two-shot series for adults consists of 30-microgram doses.) Younger kids tend to get smaller doses of vaccines because of the need to balance their robust response to the shots with keeping expected side effects, like fever, manageable (SN: 2/25/21).

Determining how well a vaccine is expected to work in children is tested differently than in adults. The adult COVID-19 vaccine trials included tens of thousands of people per trial, enough to determine the efficacy of the vaccines (SN: 10/4/20). That’s a measure of how well the shots protect those in the vaccinated group compared with those given a placebo, based on how many cases occur in each group. For kids, it would have taken even larger trials to have enough COVID-19 cases (since overall totals among kids have been lower than for adults) for a close read on efficacy.

So as a proxy for efficacy, the trials compared the antibody response kids generate to the shots with what was measured for the youngest adults in the efficacy trials. For Moderna, the comparison group is 18- to 25-year-olds, while for Pfizer, the response is matched against those 16 to 25 years old (Pfizer included older teens in their adult trial).

Among more than 6,600 participants, Moderna reported that the little kids’ antibody response to its two-dose series met that seen among the young adult comparison group. Pfizer reported the same for the more than 4,500 participants in its young kids’ trial: the three-dose series produced antibody levels that reached that seen among the 16- to 25-year-old comparison group, which had gotten two shots.

The advisory committee also reviewed the safety of the vaccines for little kids. There were no alarming allergic reactions to the shots, no deaths and no cases of heart inflammation, a very rare side effect of COVID-19 mRNA vaccines (SN: 6/23/21) that poses a much higher risk during COVID-19 illness. Common side effects for both vaccines included sore arms, crying, irritability, sleepiness and fever. It’s fine to give pain relievers after vaccination for children with fever or soreness, Oliver said at the CDC’s advisory committee meeting.

Once the vaccines get the go-ahead, close to 20 percent of parents of the very young plan to be in line right away, according to the Kaiser Family Foundation’s COVID-19 Vaccine Monitor. The survey from mid-April reported that another 38 percent plan to wait and see how things go with the vaccine rollout before deciding, while 11 percent say they will get their youngest immunized only if the shots are required. That leaves 27 percent in the “definitely not” category, which is similar to the percentage of parents who say they won’t vaccinate kids 5 and up.

An issue that remains is whether the littlest kids will need boosters added to the initial series of shots, as adults and older kids have. For immunocompromised children, a third dose of Moderna would be included in the initial series of shots, based on data for older children and adults who are immunocompromised and were vaccinated with Moderna. There isn’t yet data on whether another dose should be added for the Pfizer series of three shots for young children who are immunocompromised.

Safety monitoring for COVID-19 vaccines will also continue, through different U.S. surveillance systems such as the Vaccine Adverse Event Reporting System. So far, around 600 million doses of the COVID-19 vaccines have been given in the United States, and the safety demonstrated is reassuring, said FDA committee member Henry Bernstein, a pediatrician at Cohen Children’s Medical Center in New Hyde Park, N.Y. “I think having a COVID vaccine available for this younger population is critically important, given that pediatric cases can be, [have] been and may be problematic in the future.”

Originally published by Science News, a nonprofit newsroom. Republished here with permission.
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