WASHINGTON — Over the past 10 months, while tens of millions of children and adolescents have received the Pfizer-BioNTech vaccine, the companies’ main competitor, Moderna, has been left out, as its vaccines were limited to adults.
Now, however, Moderna may be ready to return to the scene at a critical point in the national vaccination campaign. This week the company is expected to send official authorities initial data on how well the coronavirus vaccine works in the country’s youngest children.
About 18 million children under the age of 5 are the only Americans not yet eligible to receive the vaccine. And while vaccination has been slow among older children, many parents are still eagerly awaiting the opportunity to protect their infants, toddlers and preschoolers.
Moderna is in a fierce fight with Pfizer-BioNTech for the opportunity to vaccinate this group and is hopeful that it has found what some scientists call the “Goldilocks” dose, one with enough potency to offer long-lasting protection, but not enough to cause worrying widespread side effects, such as high fevers.
For children under the age of 6, Moderna has opted for a two-dose regimen at one-fourth the strength of its adult dose. Pfizer is expected to seek authorization next month for a three-vaccine regimen for children under 5, with one-tenth the strength of the dose for people over 11.
Moderna is also expected to soon release data on its clinical trial in the following age group: children ages 6 to 11.
Yvonne Maldonado, a professor of pediatric infectious diseases at Stanford University and one of the principal investigators at Pfizer’s Stanford facility for pediatric vaccine trials, said the data Moderna and BioNTech provide in the coming weeks will be key to understanding the effectiveness of pediatric vaccines. Maldonado said the researchers were looking closely at whether the stronger doses of Moderna “result in more robust immune responses” than Pfizer’s vaccines have in young children.
Moderna’s options have sparked interest among federal scientists and vaccine experts, as a series of studies have raised questions regarding the protection time of Pfizer’s less potent vaccines in school-age children.
In the opinion of Ofer Levy, a pediatric expert at Harvard Medical School and a member of the Food and Drug Administration’s (FDA) independent advisory committee on vaccines, Pfizer may have chosen a dose too low for children between the ages of 5 and 11 “because of the understandable priority of maximizing safety.”
To date, Pfizer has been the only one involved in vaccinating the youngest in the United States, following obtaining authorization to inoculate people between the ages of 12 and 15 in May, and then to vaccinate children between the ages of 5 and 5 in October. and 11 years.
Moderna sought approval to vaccinate adolescents in June, but the FDA delayed reviewing the application because of concerns regarding the risk of myocarditis, an inflamed heart condition that has been linked to both Modern like those of Pfizer.
Currently in the United States, more than 22 million people under the age of 18 are fully vaccinated with Pfizer, but uptake has leveled off. For example, almost one in four children between the ages of 5 and 11 have the full schedule, even though that group has been offered the vaccines for more than four months.
However, there remains a demand to protect younger children as more people have stopped wearing masks in the country, more parents have returned to the workplace and the summer travel season approaches.
Compared to adults, “the benefit of an effective vaccine in children is certainly less, because few of them get very sick,” said Eric Rubin, an infectious disease expert at the TH Chan School of Public Health in New York. Harvard University and a member of an FDA advisory panel.
“But it will benefit some individuals,” Rubin said. “It will save some lives.” According to the Centers for Disease Control and Prevention (CDC), 336 American children under the age of 5 have died of COVID-19.
Hopes rose for early coverage for younger children last month following regulators pressed Pfizer-BioNTech to submit preliminary results on its third-dose trial. The FDA wanted to start the vaccination campaign with two doses while waiting for the final results of the third.
However, that effort collapsed when new data from Pfizer encompassing more information from the omicron wave convincingly showed that two doses did not adequately protect once morest a symptomatic infection.
Now, around the same time, more detailed results from the Pfizer and Moderna trials are materializing. And while neither company yet knows whether their vaccines will be effective enough for the younger age group, both say their research shows the vaccines are safe.
“We haven’t seen anything inappropriate so far, so we’re confident in the safety profile,” said Paul Burton, Moderna’s chief medical officer.
Pfizer spokeswoman Amy Rose said that following careful research, Pfizer-BioNTech chose “the safest and most tolerable dose” for the youngest children. The companies have stated that they expect a three-vaccine regimen to provide strong protection for children under 5 years of age.
Moderna is proposing a substantially higher dose than Pfizer’s in all three pediatric age groups: 100 micrograms, the full adult dose, for ages 12 to 17; 50 micrograms for children between 6 and 11 years old; and 25 micrograms for those under 6 years of age. Regulators are likely to review the company’s data for all three age groups at the same time.
“We really defend those doses,” Burton said. Although federal authorities say there is a decline in the potency of the Pfizer and Moderna vaccines over time, some studies in adults suggest that Moderna’s protection lasts longer.
Burton mentioned that initial results showed that a 50-microgram dose of Moderna produced a “robust immune response” in children between the ages of 6 and 11. Although the total number of infections was small, the researchers hope the trial will help reveal how effective the vaccine is in preventing disease, and not just how much it raises antibody levels.
Philip Krause, a retired senior vaccine regulator at the FDA, said the agency spent much of the past year concerned regarding the safety of people under 18 from Moderna’s vaccine, with some studies showing an increased risk of myocarditis from the company’s vaccine than from Pfizer’s.
In part because of concerns regarding myocarditis, the CDC recently encouraged some people over the age of 11, particularly boys and men ages 12 to 39, to wait eight weeks between the first and second doses of Pfizer or Moderna. Studies have shown that teenagers and young men are at higher risk of developing the side effect.
Burton noted that the research had generally produced calm, including recent data from the UK showing that myocarditis was very rare and often mild for both Pfizer and Moderna vaccine recipients.
However, Walid Gellad, a drug safety expert at the University of Pittsburgh, said it was not yet known whether a higher dose of Moderna might raise the risk of myocarditis in young children. Most likely, the company’s pediatric studies are too small to identify the risk of the side effect, Gellad and other experts said.
Amid all the questions, one thing is clear: hesitating over which vaccine will be best for young children might discourage uptake.
Alison Buttenheim, a behavioral health expert at the University of Pennsylvania, said the certainty reassured those considering getting vaccinated. Otherwise, “this will just pave the way to say, ‘I’m going to wait,'” she said. “A lot of people don’t feel comfortable when science keeps changing their minds.”
