Why a Covid-19 vaccine isn’t available for kids yet

By John Bonifield, CNN

Americans 12 and older can get a Covid-19 vaccine, but younger children are still waiting.

With many schools across the United States now just weeks from reopening for the fall semester, pharmaceutical companies Pfizer and Moderna are still doing clinical trials to see how coronavirus vaccines work in children under 12 — if they’re safe and what the right dose should be.

Meanwhile, all but four states are seeing an increasing trend in cases, with doctors describing patients who are younger and sicker than what they saw in the winter.

The surge in cases has many parents of children under 12 asking when their little and not-so-little ones can get the vaccine. The answer is that it’s going to be months, if not longer. It’s not as simple as administering available adult doses to younger people.

“I understand parents’ concern in wanting their children to get vaccinated, but we have to make sure we’re doing the best and safest thing for children,” Dr. Chip Walter, a pediatrician at Duke University and an investigator for the Pfizer trials, said.

When we might be able to vaccinate children under 12

Pfizer’s vaccine study is enrolling more than 4,600 children in three age groups: 5-to-11-year-olds; 2-to-5-year-olds; and babies 6 months up to age 2.

Data for children 5 to 11 could come sometime in September and depending on the findings, the company told CNN it could ask the US Food and Drug Administration to authorize emergency use of the vaccine that same month.

Data for 2-to-5-year-olds could arrive soon after. For the youngest children, Pfizer said it could potentially get data in October or November, and shortly thereafter ask the FDA to authorize emergency use.

Emergency use considerations by the FDA can take several weeks, meaning a vaccine for younger children likely won’t be available until late fall or even next year.

Moderna’s vaccine study is enrolling about 6,700 children ages 6 months to 11 years. It declined to provide a timeline to CNN on when it could potentially have trial data results.

“The companies have said the fall … I’d be surprised if they can move that quickly, although I suppose it’s possible,” Dr. Peter Hotez, a vaccinologist and dean of the National School of Tropical Medicine at Baylor College of Medicine, said.

“I can’t imagine that we’d be in a position to even consider how to use these vaccines until the very end of the calendar year of 2021, going into the first quarter of 2022,” said Dr. Buddy Creech, a pediatric infectious disease specialist at Vanderbilt University and one of the lead investigators for Moderna’s pediatric Covid-19 vaccine. “I love that we’re riding the success of how quickly we were able to get a vaccine for adults, but we’ve just got to be patient.”

‘Children are not just little adults’

A year and a half into the pandemic, parents might wonder why isn’t there a vaccine for younger children yet. After all, some young kids are just as big as older children for whom the vaccine is authorized.

“Boy, have I had this discussion with several parents,” said Dr. William Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University and a vaccine adviser to the US Centers for Disease Control and Prevention. “It doesn’t have anything to do with size. It has everything to do with maturity of the immune system, and that doesn’t correlate one-to-one with the size of the child.”

Young children may need different doses. They may need a different number of doses. They may not need as many doses.

“We don’t know for young kids,” Creech said. “Children are not just little adults.”

And children aren’t all the same, either.

“What you may see in a child that’s six months of age may differ from what you see in a child that’s 3 years of age versus a child who’s 8 years of age, or versus an adolescent who’s 13 or 14. So, you really kind of need to take each age separately and evaluate the vaccines,” Walter said.

Creech said finding the “Goldilocks dose” for young children takes time. Give too little and the child may not make enough of an immune response to the coronavirus. Then they’re getting a vaccine with the potential for side effects with little or no benefit.

“We never like to do that. That’s away from goodness,” Creech said.

But give children too much and the balance swings in the other direction.

“You’re getting a good immune response, but you’re unnecessarily triggering things like fever, arm pain, fatigue and fussiness,” he said. “If I get a vaccine and my arm hurts for the day, my wife might make fun of me, but it’s not that big of a deal. I’ll just whine a little bit. But if a two-year-old gets a shot in the thigh, has such severe leg pain that they can’t crawl or walk, well now we’ve got a different issue, and that produces a great deal more anxiety.”

Watching for effects in children

For kids who may be on the cusp of being eligible, the reason they can’t get the vaccine is also, in part, a bit arbitrary.

“Certainly some children are bigger than others. You might have a really large 10-year-old who’s the size of a 12-year-old where the vaccine’s indicated, but in general we work on recommendations for certain age groups and it’s really best to go by that guidance,” Walter said.

Hotez and Creech agreed.

“Is there something dramatically different between an 11-year-old and a 12-year-old? Probably not. But you’ve got to draw a line somewhere, and historically, the FDA has considered preteens to be different than teenagers from a regulatory standpoint,” Creech said.

“Why was the decision made to do it at 12 instead of 11 or 10 or 14, that I don’t know. I guess you could have moved that goal post either way, probably,” Hotez said.

Another reason the vaccine is moving slowly: the companies want to make sure it doesn’t make children who get Covid-19 sicker, a scenario called immune enhancement. That’s based on what happened in the 1960s with a vaccine that was supposed to defend against RSV, respiratory syncytial virus infection, Hotez said.

“It caused this immune enhancement phenomena that actually made the disease worse, so I think that would be one consideration — making certain that’s not happening,” he said.

Hotez said the companies also want to make sure the vaccine doesn’t worsen a rare but serious post-Covid-19 related disease called multisystem inflammatory syndrome in children or MIS-C. In some instances, it has led to neurological abnormalities and deaths.

“You want to make sure the vaccine is not worsening that,” Hotez said. “That may take more time in order to convince both the companies and the regulators that these kinds of phenomenon are not occurring.”

One more reason a vaccine for younger children is taking time: for Covid-19, it was evident that older people were more seriously affected, so the vaccine trials started with them.

“Children were not considered to be a high risk from dying from this virus, which is true,” said Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital in Philadelphia and vaccine adviser to the FDA. “In the scheme of things, when you were trying to do the best you could, as quick as you could, children were not a priority.”

Testing vaccines in adults first is a very traditional way of assessing them, Schaffner said.

“You let the the first people who volunteer to get these vaccines be older adults, and then middle aged adults, and then we work our way down the age ladder,” he said. “Somebody may ask, ‘Gee, why don’t you do them simultaneously?’ Well, there’s not that bandwidth. You just can’t do too many trials simultaneously.”

Schaffner said in the end, the pace should reassure parents.

“There are a lot of parents who are very wary of giving these vaccines to children, and they want to be assured that these vaccines are indeed, as we say, safe and effective,” he said. “Do younger children need the same dose? Are they going to have a different spectrum of side effects than do older adults? All of these things have to be worked out very carefully, so we can be transparent and honest when we talk to parents about getting, for example, a six year old vaccinated.”

Covid-19 and the risk to children

Although far more rare than in adults, children can suffer, be hospitalized and die from the coronavirus. Plus, this virus does something other viruses that have vaccines, like chickenpox and measles, do not do; it can cause long-term side effects — post-infection phenomena like MIS-C and also long Covid-19, where symptoms can drag on for months.

For now, while the world waits for a vaccine, unvaccinated young children remain vulnerable.

“Kids are going to continue to be exposed. Kids are going to continue to transmit, although it seems, at least based on our experience so far in the pandemic, that they may be less efficient at that than adult counterparts,” Creech said.

This has Offit concerned about the coming school year, when young children will return to classrooms unvaccinated.

“If I have a 10- and 8-year-old child, I would really be nervous to send them back to school,” he said. “I certainly would want them to be masked and social distance as much as possible, but I’d also have to expect the school did that — that everybody in the school did that — and that’s a lot to ask. I think in many schools that won’t happen.”

The US Centers for Disease Control and Prevention last week updated its Covid-19 guidance for schools to emphasize in-person schooling is a priority in the fall, regardless of whether all mitigation measures can be implemented. Vaccination, it said, is a key safety measure, but more layers of protection — such as masks and social distancing — may be appropriate, too.

Hotez said parents’ concerns may vary depending on where their children attend school in the country.

“If you’re in Vermont and Massachusetts, or up in the Northeast or parts of the West Coast, so many people are vaccinated — such a high percentage of adults and adolescents are vaccinated — that that will have the collateral benefit of stopping or slowing transmission so that even the little kids can go back to school,” he said.

But Hotez said that’s not the case in other parts of the country, such as Tennessee, Alabama, Mississippi, Louisiana and Texas, where the Delta variant is accelerating among adult populations that remain significantly undervaccinated.

“There’s going to be quite a lot of transmission in the schools,” he said. “We know this may not go well in the fall.”

Creech was more optimistic about the coming school year.

“We have some experience from last year when the pandemic raged, and in some areas of our country schools were reopened. I think we can do in-person education in a way that is very reasonable for children,” he said. “We do know that there are some risk mitigation strategies that we can deploy.”

Right now, the best way to protect young children who can’t get vaccinated is to get everybody in a community vaccinated.

“I can’t think of a higher calling than to get a shot in the arm to protect not just myself, but those around me, particularly those that are most vulnerable,” Creech said. “If we can’t get enthusiastic about protecting the vulnerable around us, and the children around us, then we’ve got bigger problems than the pandemic.”

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