As COVID-19 vaccines are being administered to anyone age 12 and up, America’s youngest children remain the last group that cannot get a vaccination. The reopening of society this summer and the development of viral mutations leaves those children exposed in new ways, even while clinical trials are underway to develop vaccines for them.
In this rapidly changing environment, researchers and policymakers want to know: Will the disease spread more among children as they return to camps, sports, and school, especially as the virus mutates? Will enough people get vaccinated in some communities to adequately protect children until a vaccine for them arrives? Does the risk of illness from COVID-19 outweigh the potential side effects of the vaccinations for some of them?
Here is the latest information about these and other questions.
Children represent a small but growing share of infections
Children have always made up a small share of the nation’s COVID-19 infections, serious illnesses, and deaths compared with other age groups, but some think that might change as society moves to the next stages of the pandemic.
The nearly 4 million children diagnosed with COVID-19 so far account for 14% of cases, according to a recent report by the American Academy of Pediatrics (AAP) and the Children’s Hospital Association (CHA).
By and large, “it’s a disease that spreads from adults to adults,” says H. Cody Meissner, MD, chief of the Division of Pediatric Infectious Disease at Tufts Medical Center in Boston and a member of the Vaccines and Related Biological Products Advisory Committee (VRBPAC) of the Food and Drug Administration (FDA).
Others say that’s not clear yet, because the virus is mutating while people’s virus-related behaviors change as well: Many are getting vaccinated, pocketing their masks, and gathering again, including at such venues as summer camps. Those new dynamics might leave unvaccinated children more susceptible to catching the virus than they were before.
“I don’t think we know COVID well enough to call it an adult or kids’ disease,” notes A. Oveta Fuller, PhD, an associate professor of microbiology and immunology at the University of Michigan Medical School in Ann Arbor and a recent temporary voting member of the VRBPAC.
That committee, which advises the FDA on the approval of vaccines, will take into account developments like this: The number of infected children reported each week has fallen from a peak of 211,000 in mid-January to 8,447 for the week ending June 24, according to the AAP/CHA report. In recent weeks, however, the declines have slowed and even reversed a bit. Meanwhile, cases have dropped rapidly in other age groups, as adults and adolescents develop immunity through vaccines or infection, so that young children make up a larger share of new cases.
Most infected children get mild symptoms, but serious illnesses exceed those from other childhood viruses
Of the almost 600,000 deaths attributed to COVID-19 in the United States in just over 17 months, about 325 have been people under the age of 18, according to the Centers for Disease Control and Prevention (CDC). The CDC also reports that hospitalization rates are lower for children and adolescents than for adults.
But in the context of diseases associated with children, COVID-19 causes more deaths and hospitalizations than several viral diseases that have been deemed severe enough to prompt the development of vaccines (such as chickenpox), and it appears to be surpassing the flu. Children’s hospitalization rates for COVID-19 “are in the range … of what we see for influenza in any given season,” Evan Anderson, MD, an associate professor of pediatrics at Emory University School of Medicine in Atlanta, reported in a recent webinar hosted by the American College of Medical Toxicology.
The flu typically kills about 100 children a year, with totals ranging from 39 to 199 in recent years, according to the CDC. At current rates, child deaths related to COVID-19 stand at more than 200 a year.
Evidence is also emerging about the long-term effects of COVID-19 on young people, including fatigue, headaches, and loss of the sense of taste or smell for months, as well as long-term brain loss. A study in the United Kingdom found that “it is becoming increasingly apparent that a large number of children with symptomatic and asymptomatic COVID-19 are experiencing long-term effects, many months after the initial infection.”
Adult vaccinations can protect children to an extent, but children need their own vaccine
Because of expanding immunity through vaccinations and infections, the nation can minimize the spread of the virus even to those who are not vaccinated — although “you do need population immunity to get through a pandemic,” says Monica Gandhi, MD, MPH, associate division chief of the Division of HIV, Infectious Diseases, and Global Medicine at the University of California, San Francisco School of Medicine.
A study published in June in Nature Medicine examined the effect of vaccinated populations on unvaccinated children in Israel, which began a rapid COVID-19 inoculation campaign in December 2020 for everyone over age 15. The researchers calculated that for every 20 percentage point increase in people who were vaccinated within a community, positive COVID-19 tests among unvaccinated children (under 15) dropped by half.
“Until more information is available about the safety of mRNA vaccines in children and adolescents, the best way to protect children is to vaccinate as many adults as we can,” Meissner explains.
Nevertheless, experts believe that unless the vast majority of the nation gets vaccinated, the virus will continue to spread among unprotected people and mutate, creating new variants that might circumvent current vaccine protections. Just 46% of the U.S. population is fully vaccinated, according to the CDC, and vaccine hesitancy has significantly slowed vaccinations in recent weeks. Vaccination coverage varies widely depending on where people live: Full vaccination rates range from more than 65% in Vermont down to 29% in Mississippi.
In addition, the more than 33 million people who have had COVID-19 are believed to have some level of immunity. However, no one knows how long immunity from infection or vaccination will last, and waning immunities would provide another opening for the virus.
“If children are not protected, the virus will adapt” within them and continue spreading, Fuller says. “I do not believe we can control this without getting some vaccinations into children.”
Schools and youth activities pose risks but can operate safely with the right conditions
One theory for the relatively low number of children infected so far is that many were shielded from the virus by the widespread closing of schools and other group activities for about a year after the start of the pandemic. “Many of our children have been isolated at home until recently, so we have not seen a huge impact in terms of disease, hospitalization, and death,” Fuller explains. “That doesn’t mean it can’t happen” as children return to in-person recreational and educational activities this summer and fall.
So far, youth camps and sports have had spotty records regarding the spread of the coronavirus. Several studies — such as one of 91,000 youth soccer players and another of 30,000 high school athletes — determined that participants who contracted the disease usually got it from their homes and communities. However, in June the Illinois Department of Public Health revealed a COVID-19 outbreak at a summer camp that infected 85 people, mostly teens. The CDC determined that failure to follow masking and indoor ventilation guidelines fueled an outbreak that struck 44% of nearly 600 youth at a camp in Georgia last summer. And this spring, a high school wrestling league in Louisiana suspended its season because of COVID-19 outbreaks tied to a tournament.
“There is increased risk of spreading COVID-19 while playing close-contact or indoor sports,” the CDC notes.
Indoor gatherings of unvaccinated children will increase when schools reopen this fall. Assessments of schools that held in-person classes during this past academic year found that they can operate without causing viral outbreaks. Schools that did suffer widespread outbreaks — such as in several areas of Texas and in Canyon County, Utah — largely did not follow COVID-19 mitigation practices (such as masking and social distancing) and were in communities where the virus was spreading significantly.
What remains to be seen this fall, Fuller says, is how the virus spreads to children as they live in an unprecedented environment: fully interacting in schools and communities with people who have mixed levels of immunization and practice varying degrees of viral protection while the virus mutates.
A children’s vaccine is on the way — but it’s unclear how soon
The makers of the first two COVID-19 vaccines authorized for use in the United States (the mRNA vaccines made by Pfizer and Moderna) are running clinical trials on vaccines for children under 12. The trials are testing doses that are a fraction of those used in the vaccines that are administered to adults (30 milligrams): Pfizer announced in June that its next trial phases will test doses of 10 milligrams for those ages 5 to 11 and 3 milligrams for children from 6 months to 4 years old.
The companies are expected to announce results in the fall, then apply for emergency use authorizations (EUAs), which would grant immediate, temporary permission to administer the vaccines to the public. That’s what the FDA provided for the vaccines currently in use.
“We hope that as we approach the end of this calendar year, we'll have enough information to vaccinate children of any age," Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, told CNN in June.
But a lot can change between now and then. Aside from assessing the data that Pfizer and Moderna will present from their trials, the FDA and its VRBPAC will consider the state of the pandemic at that time and the effects of the vaccines currently in use, particularly among children and young adults.
For example, CDC officials announced on June 23 that there is a “likely association” between the two mRNA vaccines and myocarditis, a rare form of heart inflammation. The agency told its Advisory Committee on Immunization Practices — which makes recommendations on the use of existing vaccines — that there have been 1,226 reports of myocarditis out of about 300 million mRNA vaccinations, mostly in males ages 12 to 39. It noted that most cases were mild — with symptoms that included fatigue, chest pain, and disturbances in heart rhythm — and cleared up within several days. No fatalities were reported.
"Myocarditis is a concern and it has to be closely monitored,” Fuller says. “To me, COVID-19 infection and disease possibilities for children are the greater concern."
The issue before the FDA will be how much of a risk COVID-19 presents to younger children when weighed against any potential risks from vaccine side effects. The agency could wait for more data to issue an EUA, or it could put the vaccines through the standard biologics license application, which takes longer (typically one to two years) and requires more testing data but does not expire.
Experts agree that vaccinating children will be key to protecting them. The question will be when there’s enough evidence to move ahead. Fauci told a Senate hearing in March that vaccinating children is key for the nation to reach herd immunity.
"We don't really know what that magical point of herd immunity is, but we do know that if we get the overwhelming population vaccinated, we're going to be in good shape,” Fauci said in the hearing. “We ultimately … have to get children into that mix.”