Which covid vaccine is effective for young children?

WASHINGTON — Over the past 10 months, as tens of millions of children and adolescents have received the Pfizer-BioNTech vaccine, the companies’ main competitor, Moderna, has been sidelined because its vaccines were limited to adults.

Now, however, Moderna may be ready to return to the scene at a critical time in the national vaccination campaign. This week, the company is expected to send official authorities the first data on the performance of the coronavirus vaccine in the country’s youngest children.

About 18 million children under age 5 are the only Americans who are not yet eligible to receive the vaccine. And although vaccination has been slow in older children, many parents are still eagerly awaiting the opportunity to protect their infants, toddlers and preschoolers.

Moderna is in a tug of war with Pfizer-BioNTech for the opportunity to vaccinate this group and hopes to have found what some scientists call the “Goldilocks” dose: a dose strong enough to provide lasting protection, but not strong enough to cause Worrying general side effects, such as high fevers.

For children under 6, Moderna opted for a two-dose regimen at a quarter of the strength of its adult dose. Next month, Pfizer is expected to seek approval for a three-bite regimen for children under 5, with one-tenth the dose for people over 11.

Moderna is also expected to soon release data from its clinical trial in the following age group: children 6-11 years old.

Yvonne Maldonado, professor of pediatric infectious diseases at Stanford University and one of the principal investigators at Stanford’s Pfizer Facility for Pediatric Vaccine Trials, said data provided by Moderna and BioNTech in the coming weeks will be essential to understanding the efficacy of pediatric vaccines. Maldonado said the researchers were looking at whether higher doses of Moderna “lead to more robust immune responses” than Pfizer’s vaccines in young children.

Moderna’s options have piqued the interest of federal scientists and vaccine experts as a series of studies have raised questions about how long Pfizer’s less potent vaccines will protect in school-aged children.

Ofer Levy, a pediatric expert at Harvard Medical School and a member of the Food and Drug Administration’s (FDA) Independent Vaccine Advisory Board, thinks Pfizer may have chosen too low a dose for older children. 5 to 11 years old. because of the priority of maximizing safety”.

To date, Pfizer is the only company involved in vaccinating the youngest in the United States, having obtained authorization to vaccinate people aged 12 to 15 in May, then in October to vaccinate children aged 5 to 11 years old. Adult clearance includes 16 and 17 year olds.

Moderna applied for approval to vaccinate teenagers in June, but the FDA delayed reviewing the application due to concerns about the risk of myocarditis, an inflamed heart condition that has been linked to both Moderna and those from Pfizer.

Currently in the United States, more than 22 million people under the age of 18 are fully immunized with Pfizer, but uptake has leveled off. For example, only about one in four children between the ages of 5 and 11 have the full schedule, even though this group was offered vaccines for more than four months.

However, there is still a demand to protect young children as more people in the country have stopped wearing masks, more parents have returned to the workplace and the summer travel season is approaching.

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 the United States. Harvard University and a member of an FDA advisory committee.

“But it will benefit some people,” Rubin said. “It will save lives.” According to the Centers for Disease Control and Prevention (CDC), 336 American children under the age of 5 have died from COVID-19.

Hopes rose for early coverage of young children last month after regulators pressed Pfizer-BioNTech to submit preliminary results from its third-dose trial. The FDA wanted to start the vaccination campaign with two doses, pending the final results of the third.

This effort, however, fell apart when new data from Pfizer encompassing more information about the omicron wave convincingly showed that two doses did not adequately protect against symptomatic infection.

Now, around the same time, more detailed results from the Pfizer and Moderna trials are coming out. 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.

Amy Rose, spokeswoman for Pfizer, said that after extensive research, the Pfizer-BioNTech companies had chosen “the safest and most tolerable dose” for young children. The companies said they expected a three-vaccine regimen to provide strong protection for children under 5. Pfizer is testing a 10-microgram dose for children ages 5 to 11, one-third the dose for adults and adolescents; and 3 micrograms for children under 5 years old.

Moderna offers a significantly higher dose than Pfizer 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 children under 6 years old. Regulators are likely to review the company’s data for all three age groups at the same time.

“We really support these doses,” Burton said. Although federal authorities say there is a decrease in the potency of the Pfizer and Moderna vaccines over time, some studies in adults suggest Moderna’s protection lasts longer. “I think it all comes down to dosage,” Burton said.

Burton said early results showed a 50-microgram dose of Moderna produced a “robust immune response” in children ages 6 to 11. Although the total number of infections is small, the researchers hope the trial will help reveal how effective the vaccine is in preventing the disease, not just how much it boosts antibody levels.

Philip Krause, a now-retired senior vaccine regulator at the FDA, said the agency had spent much of the past year concerned about the safety of people under 18 from the vaccine. from Moderna, with some studies showing an increased risk of myocarditis in that company’s vaccine than in Pfizer.

“The question is always, what is the dose that elicits an immune response that we think is likely to be protective?” he said. “You can’t test the rate of myocarditis because it’s rare, but you can ask, ‘What are we sacrificing in the immune response by lowering the dose? And do we think it’s important?

Partly because of concerns about myocarditis, the CDC recently encouraged some people over the age of 11, especially boys and men ages 12 to 39, to wait eight weeks between their first and second dose of Pfizer. or Modern. Studies have shown that teenagers and young men are at a 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 Pfizer and Moderna vaccinees.

However, Walid Gellad, a drug safety expert at the University of Pittsburgh, said it’s not yet known whether a higher dose of Moderna might increase the risk of myocarditis in young children. According to Gellad and other experts, the company’s pediatric studies are likely too small to identify the risk of this side effect.

Moderna’s new attempt also comes after several studies questioned the protection of two doses of the Pfizer-BioNTech vaccine in children aged 5 to 11. Researchers from the New York State Department of Health recently found that the protection against infection offered by two doses waned significantly within weeks. For their part, CDC researchers found that during the omicron wave, the effectiveness of two doses of Pfizer’s vaccine against milder forms of the disease decreased significantly in children aged 5 to 11 years.

The studies are fueling a debate among vaccine experts about whether a more concentrated dose might have been better or whether these children need a third dose. Booster doses have been authorized for anyone over the age of 12. Pfizer expects the results of its study of a three-dose regimen for young children next month.

Gellad said it’s possible that Pfizer’s dose for children ages 5 to 11 is too low, but scientists couldn’t say for sure yet. He said he hoped regulators would be especially careful when considering higher doses for young children, because the comparative risks of this group getting sick now and becoming seriously ill are lower.

Amid all the questions, one thing is clear: hesitation over which vaccine is best for young children could discourage uptake.

Alison Buttenheim, a behavioral health expert at the University of Pennsylvania, said the certainty reassured those considering getting the shot. Otherwise, “it will just pave the way to say, ‘I’m going to wait,'” he said. “A lot of people don’t feel comfortable when science keeps changing its mind.”

Sharon LaFraniere is an investigative journalist. He was part of the team that won the Pulitzer Prize in 2018 for its investigations into Donald Trump’s ties to Russia. @SharonLNYT

Noah Weiland covers the coronavirus pandemic as a health reporter in the Washington bureau of The New York Times. He was part of the team that won the Pulitzer Prize in 2021 for his coverage of COVID-19. He grew up in East Lansing, Michigan, and graduated from the University of Chicago. @noahweiland

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