Why Moderna’s FDA-authorized COVID shot for under 5s has edge over Pfizer’s [Updated]

Update 6/18/2022, 3:34pm ET: The Centers for Disease Control and Prevention has now recommended use of both the Moderna and Pfizer-BioNTech COVID-19 vaccines for children ages 6 months to 5 years. The CDC's Advisory Committee on Immunization Practices (ACIP) voted unanimously earlier today to recommend both vaccines after a two-day meeting to review and discuss data on them. CDC Director Rochelle Walensky quickly signed off on their recommendation this afternoon, which is the last step in the regulatory process. Administration of both vaccines can now begin. Distribution has already begun and the vaccines should be available at thousands of pediatric practices, pharmacies, health centers, local health departments, clinics, and other locations this week, according to the CDC.

"We know millions of parents and caregivers are eager to get their young children vaccinated, and with today’s decision, they can," Walensky said in a statement. "I encourage parents and caregivers with questions to talk to their doctor, nurse, or local pharmacist to learn more about the benefits of vaccinations and the importance of protecting their children by getting them vaccinated."    

Update 6/17/2022, 9:25am ET:  Two COVID-19 vaccines for infants and young children ages 6 months to under 5 years are now authorized for use by the US Food and Drug Administration. The regulator issued the authorizations early Friday, following Wednesday's unanimous endorsements of the authorizations by the agency's committee of expert advisers.

“Many parents, caregivers and clinicians have been waiting for a vaccine for younger children, and this action will help protect those down to 6 months of age," FDA Commissioner Robert M. Califf said in a statement Friday. "As we have seen with older age groups, we expect that the vaccines for younger children will provide protection from the most severe outcomes of COVID-19, such as hospitalization and death."

The authorized vaccines are both mRNA-based vaccines made by Moderna, which is now authorized for children ages 6 months to 17 years, and Pfizer-BioNTech's vaccine, which is now authorized for children ages 6 months to 4 years. Though both earned authorization and unanimous support from the FDA's experts advisers, the two vaccines are very different. Most importantly, the advisers had far more concerns about the efficacy and three-dose, three-month-long regimen of Pfizer-BioNTech's vaccine than Moderna's two-dose regimen.

Below, Ars provides a guide for parents on the most critical information about these vaccines, including why they're needed, the process going forward, detailed data on the vaccines, and commentary from FDA advisers.

Original Story 6/15/2022, 8:07pm ET: A committee of experts advising the Food and Drug Administration voiced unanimous support Wednesday for the authorization of two COVID-19 vaccines for children under the age of 5. If the FDA authorizes the vaccines, it will mark the first time during the more than two-year pandemic that vaccines against COVID-19 will be available for this age group—the last group yet to be eligible for vaccination.

The need for vaccines

Although children in this young age group have a relatively lower risk of severe disease and death from COVID-19 compared with older groups, they can and do become severely ill and die from the infection. As of last month, 45,000 children under 5 have been hospitalized for COVID-19 during the pandemic; roughly 50 percent of those hospitalizations occurred during the omicron wave. Of the children who land in the hospital, about 63 percent have no underlying medical conditions that put them at greater risk of severe COVID-19. And about a quarter of those hospitalized require intensive care.

So far, 475 children under the age of 5 have died from COVID-19 during the pandemic, making COVID-19 far deadlier than other diseases we routinely vaccinate young children against, including influenza, measles, chickenpox, hepatitis A, and rotavirus.

"I think we have to be careful that we don't become numb to the number of pediatric deaths because of the overwhelming number of older deaths," Peter Marks, FDA's top vaccine regulator, said today. "Every life is important."

Marks made his comments at the start of today's full-day gathering of the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC). The independent experts reviewed data on Moderna's vaccine for infants 6 months old to children under the age of 6 years and Pfizer-BioNTech's vaccine for infants 6 months to children under 5 years.

The committee voted unanimously—21 to 0—in support of the FDA authorizing Moderna's vaccine for infants and young children. In a second vote, they also voted unanimously—21 to 0—in support of the FDA authorizing the Pfizer-BioNTech vaccine for infants and young children.

The process

These votes are the first steps in a four-step process for getting these vaccines into tiny arms. The second step is for the FDA to decide whether to issue authorizations for both vaccines. The agency isn't obligated to follow VRBPAC's advice but typically does, and it is widely expected to do so here, likely by the end of Thursday.

The third step is for the Centers for Disease Control and Prevention to convene its advisory committee of independent vaccine experts, the Advisory Committee on Immunization Practices (ACIP), which will review the data again and vote whether to recommend the vaccines' use. The ACIP is scheduled to meet to discuss and vote on these vaccines Friday, June 17, and Saturday, June 18. If ACIP members vote in favor of the CDC recommending the use of these vaccines, then the fourth and final step will be for CDC Director Rochelle Walensky's endorsement. At that point, administration can begin.

In terms of distribution of the vaccines, the Biden administration has already put up a supply of 10 million doses—some Moderna doses and some Pfizer-BioNTech doses—for states to preorder. If or when the FDA authorizes the vaccines, then those orders can be shipped to states. If all goes to plan, orders of doses are expected to arrive in states this weekend. Assuming Walensky endorses the use of the vaccines, federal officials expect vaccine administration to begin "in earnest" starting Tuesday, June 21—given that Monday is a federal holiday observing Juneteenth.

In the meantime, parents eager to finally get their young children protected against the devastating pandemic virus will have to carefully determine which of the two vaccine options is suitable for their kids. Both vaccines are simply smaller doses of the companies' mRNA-based vaccines already approved for older age groups. But, compared with each other, they have key differences in dosing, timing of doses, efficacy estimates, and side effects.

While VRBPAC members were overwhelmingly supportive of authorizing both vaccines, they also expressed reservations over the Pfizer-BioNTech vaccine's longer three-dose, three-month-long regimen and extremely preliminary vaccine estimates.

Here's a rundown of the two vaccines, the data we have on them, and what VRBPAC members thought.