Here’s what we know so far about the Delta variant and kids

A masked student waited to climb on the playground equipment during recess at Medora Elementary School in Louisville, Kentucky in March.Jon Cherry/Getty

With COVID-19 cases rising in the United States once again, fueled by the highly transmissible Delta variant, and public health officials repeatedly warning that unvaccinated people remain most vulnerable to infections, concerns are mounting for children younger than 12 who are not yet eligible for the shots.

While Pfizer’s COVID-19 vaccine has been approved for emergency use in children 12 and older, vaccines have not yet been authorized for those younger than 12. Public health officials hope the shots will be open to younger children in the coming months, but it’s not clear when federal regulators might grant approval.

The Delta variant is now the dominant strain in the country, and data show it’s at least twice as transmissible as the Alpha variant. Here’s what we know so far about the variant and children.

Cases are rising generally, which includes infections among children

As cases rise across the country, largely among unvaccinated people, more children are becoming infected with COVID-19, Dr. Anthony Fauci said at a briefing last week by the White House COVID-19 response team.

“The Delta variant is much more highly transmissible than was Alpha,” Fauci said. “So given that, you’ll see more children likely get infected. And since you have a certain percentage of children, even though the percentage is small, [a] certain percentage of children will require hospitalization. So quantitatively, you will see more children in the hospital.”

Dr. Shira Doron, an infectious disease physician and epidemiologist at Tufts Medical Center, previously told the Globe that when infections rise across the country, they rise uniformly among the population.

“When cases are on the rise, they rise in every age group, kind of, equally,” Doron said. “They’re not rising in unvaccinated children more than they’re rising in adults.”

But the Delta variant, because of its increased transmissibility, is a “game changer,” Doron said.

“COVID was circulating before Delta arrived, but we had enough immunity due to vaccination and prior infections to have our numbers be low and dropping,” Doron said. “And now, despite the fact that it’s summer and we’re doing things outside, which worked well for us last summer, the increased transmissibility of the virus means that our levels of immunity are not high enough to keep our numbers down. With that rise, the children are less protected, and everyone’s less protected.”

Hospitalizations among children infected with COVID-19 are rising and have surpassed levels seen during the winter surge. At the same time, hospitalizations among children 17 and younger remain far below hospitalization rates for adult age groups, with people 70 and older making up the highest number of new hospital admissions per 100,000 people, according to data from the Centers for Disease Control and Prevention. In some parts of the country, largely in states with lower vaccination rates like Arkansas and Texas, officials are warning that the number of ICU beds for children is dwindling.

Though experts have said that COVID-19 is not as serious in children, Dr. Francis Collins, the director of the National Institutes of Health, said in an interview with Fox News on Sunday that rising pediatric COVID-19 cases are “very worrisome” and the contagious nature of the Delta variant puts kids at serious risk.

“I think traditionally people kind of considered kids aren’t going to get that sick with this,” Collins said. “More than 400 children have died of COVID-19, and right now we have almost 2,000 kids in the hospital — many of them in ICUs — some under the age of four. So anybody who tries to tell you, ‘Well don’t worry about the kids. The virus won’t really bother them,’ that’s not the evidence. And especially with Delta being so contagious, kids are very seriously at risk.”

While the American Academy of Pediatrics said that cases among children have increased steadily since the beginning of July after declining in early summer, it also noted that data indicate severe illness due to COVID-19 is uncommon among children.

But data suggest COVID-19 symptoms in children are more mild than in adults

Data suggest that COVID-19 infections, including those where the Delta variant is present, are more mild in children than adults, experts have said.

During the White House briefing, Fauci cited studies that found the Delta variant is more severe in adults, “namely causing more relative percentage of hospitalization and more severe disease.”

“With regard to children, this could possibly be the case, but we are not seeing this in a definitive way,” Fauci said. “The only thing we know for sure is that more infections mean more children will be in the hospital.”

Dr. Kristin Moffitt, a pediatric infectious disease physician at Boston Children’s Hospital, recently told the Globe that COVID-19 infections in children appear to be similar to a mild upper respiratory infection.

More data is needed to determine whether symptoms in children present differently if they are infected with the Delta variant, Moffitt said.

“We don’t have a ton of data yet as to whether or not the symptoms look different in children infected with the Delta variant than with other variants,” Moffitt said. “But anecdotally, it seems like there are not major differences.”

In an interview last week on ABC, Collins, the NIH director, said there is not rigorous data to show that infections among kids with the Delta variant are more serious.

“I certainly am hearing from pediatricians that they’re concerned that this time the kids who are in the hospital are both more numerous and more seriously ill,” Collins said.

Children have more protection from COVID-19 when those around them are vaccinated

Experts have said one way to protect unvaccinated children from the virus is to vaccinate the adults and eligible children around them.

“Vaccinating adults is absolutely the way to protect children,” Doron said. “In particular because the under twelves won’t have access to vaccine until it looks like 2022.”

While speaking about the return to schools this fall, Fauci said during the White House briefing that until vaccines are approved for children younger than 12, “what you want to do — what we’re recommending — is that in the school system, you surround the children with people who are vaccinated who are eligible to be vaccinated.”

“We want to see as many as possible of the teachers and the personnel in the school to be vaccinated,” Fauci said. “Children who are old enough and are eligible to get vaccinated should get vaccinated.”

A study conducted in Israel from December 2020 to March 2021 that looked at vaccination records and test results in 177 communities found that vaccination rates are connected to a decline in COVID-19 infections among people younger than 16, who at the time were unvaccinated.

On average, for each 20 percentage points of people who were vaccinated in a community, the positive test fraction for the unvaccinated group decreased about twofold, the study found, leading researchers to believe that vaccinations not only protect those who receive the shots but also unvaccinated people in the community.

When might vaccines be cleared for kids younger than 12?

In an interview with CBS last week, Fauci said studies are underway by the federal government and pharmaceutical companies to assess the vaccine’s safety and its ability to produce an immune response in younger children.

The response of children to the vaccine is being assessed in an “age de-escalation” study, Fauci said, which groups children by age.

“[We’re] doing 11 to nine, nine to six, six to two, and then six months to two years, and we’re getting good data on that right now,” Fauci said. “Ultimately it will be a regulatory decision by the FDA, which will then go on to a recommendation from the Advisory Committee on Immunization Practices.”

Fauci said he hopes the clearance from the FDA and the recommendation from the advisory panel comes “within a reasonable period of time this fall so that we can get those kids protected.”

The American Academy of Pediatrics wrote to acting FDA commissioner Janet Woodcock earlier this month urging federal authorities to clear the vaccines for children younger than 12 as soon as possible.

“In our view, the rise of the Delta variant changes the risk-benefit analysis for authorizing vaccines in children,” the letter stated. It encouraged the FDA to “strongly consider” authorizing the vaccines in children ages 5 to 11, for whom data are already available.

Moderna and Pfizer launched studies of their vaccines in children younger than 12 earlier this year. The Food and Drug Administration last month requested that the companies expand the size of their clinical trials in children between the ages of 5 and 11.

A federal official told The Washington Post that they expect authorization of a COVID-19 vaccine for children 5 to 11 years old by late October or early November.