Why Kids Tend To Have Milder COVID Cases Than Adults

A new study sheds light on a question we've been asking throughout the pandemic.

Fact checked by Sarah Scott

Most of us are aware that kids are usually spared from the most serious effects of COVID-19. Of course, some children do experience serious and long-lasting effects, but the majority do not, and this was one of the saving graces of the pandemic for many of us parents. Still, even as we've all learned to adapt with COVID in our midst, it’s remained a bit of a mystery why kids have been largely safe from severe illness.

A new study supported by the National Institutes of Health and published in Cell is shedding some light on this question. Researchers looked at the antibody responses of a group of infants who were infected with COVID, and compared this to typical antibody responses of infected adults. In a nutshell, the researchers found that infants’ immune response was located primarily in their noses, rather than their blood, which may explain why children have less severe responses to COVID.

Here, experts help us unpack this fascinating bit of research, and what it means for parents.

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Key Points of the Research

The research team studied 81 babies and young children, ages 1 month to almost 4 years. Their parents were asked to monitor them for signs of COVID. “The study consisted of monitoring for COVID-19 infection and measuring immune response by collecting weekly nasal swabs and blood samples before and after infection,” explained Behnoosh Afghani, MD, a pediatric infectious disease specialist at UCI Health, who was not involved with the study.

Of the 81 children, 54 contracted COVID and experienced mild symptoms. Researchers also examined nasal swabs and blood samples from mothers and other adults, to compare their immune response to those of these infants and children.

The study revealed the following:

• Young kids’ antibody responses are different than adults.

• Kids tended to have more nasal antibody responses than adults.

• Adults tended to have more inflammatory cytokines than children, which are proteins linked to severe COVID.

• Infants and young kids produce antibody responses that last about 300 days, whereas adult antibody responses tend to last for a shorter duration.
  

Related: Does My Child Have COVID-19 or the Stomach Flu?

Implications of the Study

As the study researchers describe, their findings point to the idea that children tend to attack the COVID virus as it enters their body through their nasal passages, before it moves through the rest of their body. This may explain the fact that COVID is usually less severe for kids, according to the researchers.

“The mucosal antibody response detected in the nasal mucosa of children was not present in adults,” explains Dr. Afghani. “Unlike children, the immune response in the blood of infected adults was mostly composed of inflammatory cytokines which explains the more severe illness in adults.”

Even though the research indicates that kids seem to produce more long-lasting antibodies, showing elevated antibody levels up to 300 days past infection, Richard Martinello, MD, a pediatric infectious diseases specialist at Yale Medicine, says there are a few caveats to keep in mind.

“While the antibodies the young children developed were effective at stopping the virus from replicating and these antibody levels remained elevated for a longer period than seen in adults, the initial amount of antibodies produced against the SARS-CoV-2 virus were not as great compared with adults,” says Dr. Martinello. “Also, the immune memory cells produced in the young children were not as great and did not last as long as compared to adults.”

Related: FDA Approves Updated COVID-19 Booster Shots to Protect Against New Variants

Why Do Some Kids Get More Serious Cases of COVID?

Although this research helps unravel the mystery of why children by and large have milder cases of COVID than adults, there are some children who do experience more severe cases. For example, some children—even if they experience mild symptoms of illness—develop long COVID symptoms. Additionally, some children experience a serious post-COVID condition called multisystem inflammatory syndrome in children (MIS-C), which causes widespread inflammation in the body and requires medical treatment and hospitalization.

So, why is it that most kids experience mild symptoms and make full recoveries from COVID while others do not? Most experts agree it’s not clear why certain healthy children develop these severe presentations while others do not, but a severe immune response might be to blame, says Zachary Hoy, a board-certified pediatric infectious disease specialist and medical director at Pediatrix Medical Group in Nashville, Tennessee.

“Some children's immune systems activate COVID too strongly with too much and nonspecific inflammation,” he explains. “This inflammation can cause multiple organs to be involved and lead to difficulty in those organs from functioning especially the heart.”

A similar mechanism is likely at play when it comes to long COVID in kids, says Dolly Sharma, MD, the director of pediatric infectious diseases at Northwell Staten Island University Hospital in New York. More serious cases of COVID may be linked to an exaggerated hyper-immune response, which is basically your immune system going into overdrive after a COVID infection, she says.

“Such a phenomenon may be implicated in producing either prolonged or hyper-exaggerated responses to COVID infection,” Dr. Sharma says.

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What Does This Mean in Terms of Kids and Vaccines?

Hearing about kids having mostly milder responses to COVID may lead you to believe that kids don’t need to be vaccinated against COVID. Likewise, learning that kids usually have longer-lasting antibodies may make you decide against getting your child the latest COVID booster, if they’ve previously been infected with COVID.

Every family should consult with their pediatrician and make a decision that works for them, but experts say that this research doesn’t mean kids don’t need recommended COVID vaccines and boosters.

“This study should not be interpreted as suggesting that vaccination for infants and young children is not important—it was not designed to address this question,” says Dr. Martinello. Vaccination is important for infants and young children because it protects them against serious disease, and complications from COVID, and protects close contact of kids (like grandparents) by decreasing the risk of infection and contagiousness, Dr. Martinello explains.

Right now, both the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC) are recommending that everyone aged 5 years and up get one dose of the updated COVID booster, which was formulated to match some of the more recently circulating COVID variants. Kids aged 6 months through four years should also be boosted but they may need more than one dose, depending on which vaccine type they are getting.

Make sure you ask your pediatrician about which COVID vaccine or booster is right for your child, and when they should receive it.

Related: Yes, You Should Get the COVID Vaccine Even If You're Trying to Get Pregnant—Here's Why

Takeaway for Parents

This study revealed important and eye-opening information about the immune response in infants and young children infected with COVID, says Dr. Afghani. While the study helps explain in part why young children generally fare well with COVID, there are more questions about kids and COVID that could be explored in future research, she says.

“We need more information about the immune response in older children and those who develop more severe disease,” according to Dr. Afghani. Either way, she emphasizes this research should not have any bearing on what parents do in terms of protecting their children from COVID. “Parents should follow the American Academy of Pediatrics and Centers for Disease Control regarding recommendations regarding vaccinations,” Dr. Afghani shares.

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