Yes, children can be affected by Covid-19. Here's why doctors say they need to be protected

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(CNN) -- The idea that kids don't get hit hard by Covid-19 is losing steam -- in part because of a variant more contagious than any we've seen before.

Since this time last year, more than 45,000 children have been hospitalized with Covid-19, according to the US Centers for Disease Control and Prevention.

As of Tuesday, an average of 192 children with Covid-19 were admitted to US hospitals every day over the past week, CDC data shows.

That's a 45.7% increase from the previous week in daily new hospitalizations among Covid-19 patients ages 0 to 17.

While adults debate school mask mandates and whether to vaccinate older kids, the now-dominant Delta variant keeps targeting those unvaccinated -- including some children too young to get inoculated.

Doctors say it's crucial to protect children against the Delta variant -- not just to preserve in-person learning and protect their own health but to help prevent even more aggressive variants from emerging.

Child Covid-19 infections and hospitalizations are spiking

Since the last school year, a more contagious variant -- Alpha -- has been replaced by an even more contagious variant -- Delta -- as the dominant strain of coronavirus in the US.

The Delta variant is as contagious as chickenpox, the CDC says. In just two months, Delta jumped from 3% to more than 93% of sequenced coronavirus samples in the US, according to the agency.

And in just one week, the US had an 84% increase in new Covid-19 cases among children, the American Academy of Pediatrics said.

The 71,726 new pediatric cases from July 22 to 29 marked "a substantial increase" from the previous week, when 39,000 new cases among children were reported, the AAP said.

And with the rise in pediatric Covid-19 hospitalizations, it's not just children with preexisting conditions getting hospitalized.

Almost half -- 46.4% -- of children hospitalized with Covid-19 between March 2020 and June 2021 had no known underlying condition, according to CDC data froms almost 100 US counties.

Covid-19 deaths in children shouldn't be ignored, CDC chief says

While children are far less likely to die from Covid-19 than adults, the deaths are still significant, CDC Director Dr. Rochelle Walensky said.

At least 416 children ages 0 to 18 have died from Covid-19, according to data from the National Center for Health Statistics.

"I think we fall into this flawed thinking of saying that only 400 of these 600,000 deaths from Covid-19 have been in children," Walensky said in July.

"Children are not supposed to die. And so 400 is a huge amount."

The number of Covid-19 deaths among children is more than twice the number of pediatric flu deaths reported by the CDC between 2019-2020, among the worst flu seasons since 2010.

The main reason why Covid-19 is deadlier for children than other infectious diseases is because many children are vaccinated against other diseases, said Dr. James Campbell, professor of pediatrics at the University of Maryland School of Medicine.

"Nobody's dying of polio, nobody's dying of measles in the United States. Nobody's dying of diphtheria," Campbell told CNN last month.

But while children ages 12 to 17 can get a Covid-19 vaccine, millions have not done so.

And it could be several more months before a vaccine is authorized for children under age 12.

Rebecca Calloway's 7-year-old daughter Georgia is one of thousands of young children testing various doses of Covid-19 vaccines to make sure they're safe and effective before they get authorized.

Part of why Calloway enrolled Georgia in the pediatric vaccine trial is because she recently lost her 3-year-old daughter to another unexpected disease -- Type 1 diabetes -- and doesn't want any more families to lose a child to Covid-19.

While childhood deaths from Covid-19 and Type 1 diabetes are rare, "You don't want to be that statistic," Calloway said.

Protecting kids from Covid-19 is critical to keep them in school in-person

With the highly contagious Delta variant, the CDC now recommends students from kindergarten through grade 12 wear masks in school, along with teachers and visitors. The American Academy of Pediatrics has recommended masks in schools for everyone over age 2.

"Our children deserve to have full-time, in person, safe learning with prevention measures in place. And that includes masking for everyone in schools," Walensky said.

Some students are returning to schools for the first time in a year. But long-awaited classroom learning can be quickly derailed by an infection or outbreak.

In Atlanta, more than 100 students at Drew Charter School had to quarantine after nine students and five staff members tested positive.

And it doesn't take much for Covid-19 to shut down a school again. Even one case can have a ripple effect on students, faculty and staff.

"We need adults to run schools, and if my adults are sick or needing to quarantine, I don't have adults present to provide the education," said Carlee Simon, superintendent of Alachua County Public Schools in Florida.

The school board voted to require face masks for the first two weeks of school, but Florida's governor has banned mask mandates in schools and threatened to reduce funding to schools that require masks.

And that has the superintendent worried.

"When we have families that don't want to have masks on their child, what they're doing is not only making the higher chance they will have to be quarantined," Simon said.

If a student gets infected, "they will also have other students who did have masks on who would also need to be quarantined."

"Everybody wants to move forward. Nobody wants to have masks forever," Simon said. But "we would like to be able to be safe and have instructional time with our students."

In addition to masks in schools, the CDC recommends layering other strategies such as improved ventilation, physical distancing and testing on a screening basis.

Children can accidentally help spur new variants

Protecting children from getting Covid-19 can help everyone in the long run, doctors say.

As coronavirus keeps spreading, replicating itself in new people, the more chances it has to mutate.

Some mutations can give the virus an advantage, and more aggressive variants can emerge -- such as ones that could evade vaccines.

"That's, of course, the concern," Walensky said.

Fully vaccinated people are less likely to get infected with the Delta variant.

But unvaccinated people -- including unvaccinated children -- are more susceptible to infection and can unknowingly help with the creation of new variants, Offit said.

"We're not going to be able to stop this pandemic until we have a significant percentage of the population (fully) vaccinated," he said.

Long Covid and MIS-C can leave lasting impacts

Just like adults, children can be susceptible to "long Covid" -- nagging symptoms weeks or months after a coronavirus infection.

"Even for young people who consider their risk of severe Covid to be low, the long-term consequences can be quite serious," Dr. Francis Collins, director of the National Institutes of Health, said this spring.

In some cases, children who start with mild or even no symptoms from Covid-19 end up hospitalized weeks or months later with a condition called MIS-C -- multisystem inflammatory syndrome in children.

MIS-C is "a rare but serious condition associated with COVID-19 in which different body parts become inflamed, including the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs," the CDC says.

It happens when "the virus induces your body to make an immune response against your own blood vessels" -- which can cause inflammation of the blood vessels, said pediatrician Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital in Philadelphia.

Often, children with MIS-C don't start off very sick with Covid-19.

"Usually children are picked up incidentally as having (coronavirus). Someone in the family was infected, a friend was infected, so they got a PCR test. And they're found to be positive. ... Then they're fine," Offit told CNN.

"Then a month goes by, and they develop a high fever. And evidence of lung, liver, kidney or heart damage. That's when they come to our hospital."

At least 4,196 cases of MIS-C had been reported between February 2020 and June 2021, including 37 deaths, the CDC said. It said 99% of MIS-C patients had tested positive for coronavirus, and the other 1% had contact with someone with Covid-19.

The median age of patients with MIS-C was 9 years old.

"CDC is working to learn more about why some children and adolescents develop MIS-C after having COVID-19 or contact with someone with COVID-19, while others do not," the CDC says.

"Based on what we know now about MIS-C, the best way you can protect your child is by taking everyday actions to prevent your child and the entire household from getting the virus that causes COVID-19."

The best steps parents can take to protect their children include getting vaccinated and vaccinating children ages 12 and up, Walensky said.

And even if a parent is fully vaccinated, there's a small chance they could catch an asymptomatic breakthrough infection and pass the virus to their children.

That's why it's a good idea for all parents of young children to wear masks in public.

But the best way to protect unvaccinated children, Walensky said, "is to surround them with vaccinated people."

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