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What Are COVID Vaccine Side Effects For Kids Under 5?

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With coronavirus vaccines now available for kids infants, toddlers and preschoolers, some are asking what side effects could accompany the shot?

The Centers for Disease Control and Prevention decided that coronavirus vaccines should be opened to children as young as 6 months, with CDC Director Dr. Rochelle Walensky giving the final signoff Saturday afternoon.

So far, studies from Moderna and Pfizer showed that side effects, including fever and fatigue, were mostly minor.

Heart inflammation sometimes occurs in teens and young adults, mostly males, after receiving either the Pfizer or Moderna vaccines.

However, the CDC recently found the risk of myocarditis and other inflammatory syndromes was higher following an infection from COVID than after Pfizer or Moderna vaccination in males and females ages 5 and older.

Moderna previously said that, armed with additional evidence, it was updating its FDA application for teen shots and requesting a green light for 6- to 11-year-olds, too. Dr. Stephen Hoge, Moderna’s president, said he’s optimistic the company will be able to offer its vaccine “across all age groups in the United States by the summer.”

Moderna says its original adult dose — two 100-microgram shots — is safe and effective in 12- to 17-year-olds. For elementary school-age kids, it’s using half the adult dose.

About 1.5 million adolescents have used the Moderna vaccine in other countries, “and so far we've seen very reassuring safety from that experience," Hoge said.

The heart risk also seems linked to puberty, and regulators in Canada, Europe and elsewhere recently expanded Moderna vaccinations to kids as young as 6.

“That concern has not been seen in the younger children,” said Northwestern’s Muller.

Why do health officials say children should be vaccinated?

While young children generally don’t get as sick from COVID-19 as older kids and adults, their hospitalizations surged during the omicron wave and FDA’s advisers determined that benefits from vaccination outweighed the minimal risks.

Walensky said pediatric deaths from COVID-19 have been higher than what is generally seen from the flu each year.

“So I actually think we need to protect young children, as well as protect everyone with the vaccine and especially protect elders,” she said.

In a study of kids ages 6 months through 5 years, two Moderna shots — each a quarter of the regular dose — triggered high levels of virus-fighting antibodies, the same amount proven to protect young adults, the company said.

The shots triggered fewer fevers than other routine vaccinations, officials said.

The vaccine proved between about 40% and 50% effective at preventing symptomatic COVID-19 during the trial. The company blamed the omicron variant's ability to partially evade vaccine immunity, noting that unboosted adults showed similarly less effectiveness against milder omicron infections.

While no children became severely ill during the study, Moderna noted high antibody levels are a proxy for protection against more serious illness — and the company will test a child booster dose.

COVID-19 vaccines aren't as effective against the super-contagious omicron mutant — in people of any age — and Moderna's study found the same trend.

At the same time, preliminary data suggested Pfizer and its partner BioNTech's three-dose series is 80% effective in preventing symptomatic COVID, the companies said, but they cautioned the calculation is based on just 10 cases diagnosed among study participants by the end of April.

The study rules state that at least 21 cases are needed to formally determine effectiveness, and Pfizer promised an update as soon as more data is available.

“The study suggests that a low, 3-microgram dose of our vaccine, carefully selected based on tolerability data, provides young children with a high level of protection against the recent COVID-19 strains,” he said in a statement.

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