How are the Pfizer and Moderna vaccines for young children different?

They both use an mRNA platform and are both considered safe and well tolerated. Pediatricians CNN spoke to across the country suggest either is a good option.

“I think they’re both very effective with very good side effect profiles and I wouldn’t hesitate to give them to my children either,” said Dr. Nina Alfieri, a pediatrician at the hospital for children Ann & Robert H. Lurie of Chicago. “I think both are very good options.”

Both appear to create protective antibodies in small children as they do in young adults. There are only subtle differences and one may suit some children better than the other.

Moderna’s Covid-19 vaccine is now licensed for children aged 6 months to 5 years. Pfizer is for children 6 months to 4 years old.

Pfizer’s vaccine was previously licensed for children as young as 5 years old. Moderna’s vaccine for people ages 6 to 17 was recently cleared by the U.S. Food and Drug Administration, and CDC vaccine advisers will vote this week on whether to recommend it.

Dose Size and Timing

A child who receives the Moderna vaccine will not need to go to the doctor or pharmacy as often, and they will be protected a little faster than the Pfizer vaccine.

The Moderna series is complete with two 25 microgram doses given one month apart. Children with weakened immune systems would receive a third injection. The Moderna plan for young children is quarter the size of adults.

With Pfizer, it takes three shots for the series to be complete. The company initially tried two doses, but trial data showed that after the second dose, the vaccine did not generate enough of an immune response. The three-dose vaccine authorized last week is one-tenth the size of Pfizer’s adult dose.

With Pfizer, the first two injections are given three weeks apart. The third can be administered at least eight weeks after the second. In total, it can take almost three months for the child to have the full series.

Later, scientists may want children to receive booster shots with either company’s vaccine.


Children were slightly more likely to have fever with the Moderna vaccine; this happened with about a quarter of trial participants, compared to less than 10% with Pfizer. Most fevers were mild. Less than 1% of all trial participants had a fever reaching 104 degrees.

“It was rare, but I feel like if we’re not honest with parents, when these things come out it will be concerning,” said Dr. Grant Paulsen, the site’s lead researcher for the Pfizer vaccine. and Moderna Covid-19. clinical trials for children 6 months to 11 years of age at Cincinnati Children’s.
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“Chances are that most kids will be fine and have really minimal issues,” he said. “The majority will not have major side effects.”

Moderna said other fever-causing illnesses were circulating during the trial, and that may have led to some of these fevers, since 10.6% of children in the trial’s placebo group who did not not received the vaccine reported a fever.

Dr. Claudia Hoyen, a pediatric infectious disease specialist at UH Rainbow Babies Hospitals in Cleveland, said she understands why parents hate to see their child develop a fever, but they should be reassured that the fever does not cause any type of harm. permanent or long-term problems and should resolve quickly on their own or in response to over-the-counter medications such as Tylenol or Motrin.

“I think if you continue that in mind and realize that, yes, it’s scary, but it can be manageable,” said Hoyen. “People should work with their pediatrician. I think a lot of kids who get the first dose may not even see a fever, but people should work with their pediatrician just in case they do and come up with a good plan and that would be the best thing to do. This should resolve itself quickly.

General side effects

Safety data from Moderna and Pfizer, approved by the FDA and CDC, found that potential side effects were mostly mild and short-lived.

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Side effects for both most commonly included pain at the injection site, and sometimes swelling or redness.

In terms of systemic or body-wide symptoms, the most common were fatigue or drowsiness. Some children had irritability or irritability, loss of appetite, headache, abdominal pain or discomfort, enlarged lymph nodes, mild diarrhea or vomiting. But everyone improved quickly.

“It’s very similar to the side effects we’ve seen in older children or in adults. About 24 hours for some children, you know, they don’t feel as good, they feel tired, they don’t have not the same. But luckily there were no serious side effects from these vaccines,” Dr. Ashish Jha, the White House’s Covid-19 response coordinator, told CBS on Monday.

Scientists found no serious or rare side effects during testing. They were watching closely for any signs that the children were developing problems with myocarditis, an inflammation of the heart muscle, as there were a handful of cases in older children and adults. But myocarditis has not been identified in trials in young children.

Vaccine efficacy

Both vaccines were tested when the Omicron variant was the dominant strain of the coronavirus. Studies show that, regardless of age or dose level, this particular variant was more successful in evading the protection afforded by either company’s vaccine.

The Omicron variant was tricky for this age group in general. Without access to a vaccine, hospitalization rates among children 5 and under were five times higher during Omicron’s peak in winter, compared to when the Delta variant was the dominant strain in summer last, according to a March report from the CDC.

Moderna was estimated to be 36.8% effective against symptomatic disease in children 2 to 5 years old and 50.6% effective against symptomatic disease in children 6 to 23 months old.

For the Pfizer vaccine, there were only 10 Covid cases in the vaccinated and placebo group of the trial – this is too small a number to estimate the effectiveness of the vaccine. Key efficacy data from the preliminary results are “encouraging,” according to the company. And the FDA said the immune response to the vaccine for children 6 to 23 months and 2 to 4 years old was comparable to the immune response of older participants, but more research will be needed.

In summary: get vaccinated

Get the vaccine available, experts said.

“I don’t think it’s clear one is better than the other. They’re different,” Paulsen said. “It’s really what parents prefer. Balancing those differences as well as, honestly, what’s available and what their pediatrician has or what the local hospital has.”

Doctors also suggest looking online or calling to find out what the local site offers. Not all locations will offer both plans. Some vaccination clinics may also not offer vaccines for small children or may have restrictions on the ages they serve. CVS stores that have MinuteClinics, for example, will vaccinate this new age group, but only if the child is 18 months or older. may be helpful. The website provides information about clinics listed by category.


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