If a COVID-19 vaccine is widely available in the nation even by next spring, it could be months — even after the start of school next fall — before it’s available for children.

The good news is children so far are less affected by the virus. The bad news? If children aren’t vaccinated, they can spread the disease to adults -- their teachers, parents and grandparents.

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“It’s a Catch-22,” says Dr. Sandra Arnold, chief of pediatric infectious disease at Le Bonheur Children’s Hospital.

“It’s probably a very good idea to vaccinate children as part of an overall vaccine strategy, but it’s going to be more protective for everybody else than it is actually in children,” Arnold said.

In the case of the novel coronavirus, the intense effort to get a vaccine has sped up the process tremendously. There are currently four vaccines in the final phase of clinical trials, including one Johnson & Johnson announced this week that will require only one shot.

Drug trials typically begin in adults, said Dr. Jon McCullers, chief operating officer in the college of medicine and chairman of the pediatric department at University of Tennessee Health Science Center and chief pediatrician at Le Bonheur Children’s Hospital.

“They’re not going to do it in children until they have proved it’s safe in adults. And in fact, it’s kind of a step-down where, ‘OK, we found it safe at 18 and above, now, we’re now going to do it in 12-18,’ ” down through toddlers and babies.

Each of the age segments take a few months to study in placebo tests; the next does not begin until the last is finished.

“Depending on how many different age groups, it could take a while to get down there,” McCullers said.

Because of the pace of the work, no trial yet has included children, pregnant women or immunocompromised adults.

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“Depending on how fast manufacturing can occur, and depending on how many vaccines are deemed successful, we don’t want to be sitting around with vaccine on the shelf and not know how to use it in these special populations,” said Dr. C. Buddy Creech, director of the Vanderbilt Vaccine Research Program and associate professor of pediatric infectious diseases.

Researchers conducting vaccine trials know that children are not simply miniature adults. Their bodies and immune responses are different. As a result, vaccine doses for them often vary, including with the flu.

“For children under 9, the first time they get a flu vaccine, they get two doses instead of just the one that we get each year,” Creech said.

“There’s nuance about giving vaccines to children and we really want to rigorously evaluate it, right? There’s a lot of trust that goes into having our children vaccinated,” Creech said.

Another issue with childhood drug trials is that children cannot give consent.

“A consenting adult can say, ‘Yes, I want to do this.’ But if you are giving it to kids who won’t have a say in it, you’ve just got to be extra careful,” McCullers said.

Scientists don’t know if the COVID-19 vaccines will react with coronaviruses associated with the common cold already in the bloodstream.

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“Maybe the youngest kids, who’ve never seen that before, will have a different response. Maybe it’s a worse response. Or maybe there’s a worse side effect or something. We just don’t know how it’s going to work,” McCullers said.

Because children have not experienced large-scale COVID disease, they will be one of the last groups vaccinated. Adults most vulnerable to the infection or at highest risk of severe disease will go first.

“That’s our front-line workers — our critical infrastructure folks — those who are over 65, particularly those who are living in assisted living or long-term care facilities, and those with medical problems,” Creech said.

But in other diseases, including flu, children are vaccinated first. Changes were made in the vaccine protocols in the mid-2000s, McCullers said, to put children at the top of the priority scale because they spread disease to adults.

It is less true with COVID. The highest number of cases by far in Shelby County and other parts of the country is among those ages 25-34, followed by those 35-44.

“Young, working-class and school-aged adults are the ones we ought to be vaccinating to prevent transmission and slow the spread,” he said.

McCullers suspects the elderly will not show as good a response in vaccine trials because their immune systems are less efficient.

And if the vaccine is not as effective in the elderly — who have the highest risk of getting and dying from COVID-19 — he suggests there will be battles about whether a limited-supply vaccine is “wasted” with them.

It’s possible studies in children could start by the end of this year, he says, “and you could have some results on children by April or something like that.”

He expects it could be months and months after the vaccine is out before it is approved for use in children.

“It’s a pandemic, so they might not be as careful as normal,” he said. “So maybe it works in adults, and instead of going stepwise down through kids, maybe they’ll just do all kids.

“There are going to be ethics panels and all kind of debate on this before they do it,” McCullers said.

Vaccines, whether everyone gets them or not, help create herd immunity, the point when 60% or more of a population is immune.

“Even though we just will not be able to directly inoculate children for some time, getting those doses into adults will still be helpful to children,” Arnold said.

Chris Hanson, a pediatrician at Laurelwood Pediatrics, gets occasional questions in the office about when the vaccine will be available for children.

“It’s unlikely that without specific pediatric testing that we will be seeing an approval for a COVID vaccine for kids in the near future,” Hanson says.

Arnold senses hesitation in parents already.

“Everybody wants something to be out there that they can take to protect themselves,” she said.

She suspects people will want to wait for more study before having their children vaccinated.

“That makes sense. I think people are just wary. At this point, it is going very quickly, which, even though that’s great, it’s a double-edge sword.

“We need things to move quickly, but quick doesn’t always engender trust, unfortunately.”