There is a clear sense of hope when, a year into the COVID-19 pandemic, the country’s top health officials announce that we are starting to turn a corner.

Vaccination is steadily on the rise, and in new guidance, the Centers for Disease Control and Prevention has signed off on hanging out indoors and mask-free post-vaccine.

More than 35 million have been fully vaccinated, or 10.5% of Americans, inching closer to the immunization rates that can finally put COVID-19’s toll in the past.

But nearly a quarter of Americans still don’t have a vaccine that’s certified as being safe for them.

Children under age 18 make up nearly a quarter of the population. By crude calculations, without vaccinating kids it would be impossible to vaccinate 80% of the population, as prescribed by Dr. Anthony Fauci, to hit herd immunity and end the COVID-19 pandemic.

As it stands, there are no vaccines approved for kids under age 16 in the U.S.; the Pfizer vaccine is the only one authorized for ages 16 and up, while the Moderna and Johnson & Johnson vaccines have only been fully tested in adults age 18 and older.

Clinical trials are now in the works. Pfizer and Moderna are running trials with participants down to age 12, with results expected this summer. Once the vaccines are proven safe in those groups, the companies will move to lower age groups.

Johnson & Johnson announced plans to test their vaccine in infants, after trials are done in 12- to 18-year-olds.

Teenagers will likely be able to get vaccinated this fall, according to Fauci, the country’s top infectious disease official. For younger age groups, the wait will likely be longer.

The science underlying why vaccines are different for children, and the vaccine development process details, explains how we got here.

Kids React Differently

In adults, side effects from the COVID-19 vaccine are mild. Most common is pain around the injection site, a sign of the immune system at work. Some people have also experienced headaches, fatigue, and nausea.

In children, experts are most focused on the fever and other systemic reactions, which are those affecting the whole body, not just one part of it.

Those reactions can show up differently in children, explains Dr. Archana Chatterjee, pediatric infectious disease specialist and the dean of the Chicago Medical School.

“A child who has fever is evaluated sometimes a little bit differently than an adult who has fever,” said Chatterjee, who is on the FDA expert panel charged with recommending vaccine authorization. She noted that information from a phone interview with Courthouse News does not reflect the opinion of the Vaccines and Related Biological Products Advisory Committee or the FDA.

Chatterjee explained that, especially in very young children, a fever could be a sign of a more serious infection, like meningitis or pneumonia.

“So those safety data for children are particularly important,” she said.

Malaise, poor appetite, and vomiting reported in some adults, especially after the second dose, could also be an indication of more serious health problems.

“Again, those symptoms in children mean something different,” Chatterjee said.

Not only might children react differently to COVID-19 vaccines; they seem to respond differently to the illness itself. Kids are less likely to get very sick from COVID-19 and may be less likely to spread the coronavirus.

So the vaccine focus began with adults since they, and especially older people, are hardest hit by the COVID-19 pandemic.

Chatterjee said that vaccine trials don’t necessarily always start with adults.

“A lot of the time, it depends on who the vaccine is directed towards,” she said.

The MMR vaccine, protecting against measles, mumps, and rubella, was targeted toward young kids, so trials in children started early in the process.

Vaccine trials to immunize against rotavirus, a leading cause of diarrhea in kids, “were almost exclusively done in children,” Chatterjee said. “That’s where the vaccine really needs to be applied and used.”

With the COVID-19 vaccines, “it became clear early on that the at-risk population was the older population, so the focus went there first.”

The reason why kids are at a lower risk for COVID-19 is “still a bit of a mystery,” Chatterjee said.

A child’s immune response is different from an adult’s, and it seems to be that children don’t typically mount the kind of immune response that can make some adults severely ill.

Still, children can still get sick from COVID-19, even those without any underlying health issues.

More than 3.2 million children in the U.S. had been infected with the coronavirus, according to March 4 data from the American Academy of Pediatrics, and 253 children have died in the COVID-19 pandemic. Tens of thousands have been hospitalized.

Although kids are a small percentage of COVID-19 deaths, the potential danger of the disease has been underplayed, said Dr. James Campbell, a pediatric infectious disease specialist and professor at the University of Maryland School of Medicine.

“When anybody dies, it’s difficult. But when a child dies, it’s especially difficult,” Campbell said, speaking as both a pediatrician and a parent.

Campbell has been a champion of testing the vaccine for kids. He co-wrote a viewpoint in September 2020, published in the journal Clinical Infectious Diseases, urging clinical trials to begin. At that time, adult trials in the U.S. had already moved into Phase 3, while trials in children had not started.

The joint effort between government regulators and drug companies succeeded in producing a Covid-19 vaccine — for adults — in record time, by overlapping vaccine development stages typically done consecutively.

But the lag between adult and child clinical trials may have extended the amount of time needed to finish the job and end the COVID-19 pandemic.

Reaching herd immunity will be incremental, Campbell noted. So even though experts agree that vaccinating kids is necessary to reach 80% of the population, we may reach some degree of herd immunity by vaccinating adults only.

However, there are other reasons to accelerate getting a vaccine to children, Campbell notes. For kids, the pandemic has “really turned their world upside down.”

Kids have had to skip sports and band practice, take classes from home — Covid-19 has disrupted their normal lives in their entirety, perhaps more so than it has for adults.

“They bear a great burden in our society for this pandemic, even if the infection itself has not been as severe,” Campbell said. “The ramifications of the infection for their lives have been very severe.”

Partially Vaccinated Families, Schools

President Joe Biden announced last week that all American adults will be vaccine-eligible by the end of May. Results for trials in kids ages 12 and up will be ready in a few months; distribution could begin by late summer.

For elementary school kids, vaccination may begin by the end of the year or early 2022, Fauci has said.

That will leave a gap of several months where many families will find themselves with vaccinated parents and unvaccinated kids.

Getting through that time will require some patience, said Dr. John Schreiber, chief of the infectious disease department at Connecticut Children’s Hospital.

“Myself included, my family — everyone’s anxious to be done with this,” Schreiber said. “That said, it’s not done yet. We have a few more months of very hard work still to get through this.”

Schreiber advised families not to travel extensively while they are only partially vaccinated.

“I’d probably still hunker down a bit,” he said.

Visits with vaccinated grandparents and parents are probably safe. So is going to school in person, especially now that more teachers are vaccine-eligible, provided schools are taking all the steps to avoid virus transmission.

What can’t happen is ending all safety protocols at once. Without enough people immunized against Covid-19, “we will have a resurgence if we do that,” Schreiber said.

“I think we’re going to have a gradual expansion to normalcy,” he said.

— By Nina Pullano, CNS