Smaller needle, lower dose, fewer side effects, same benefit: What to know about the newly authorized COVID-19 vaccine for kids

• On Tuesay, the CDC gave kids ages 5 to 11 the green light to get Pfizer's COVID-19 vaccine.
• Children will get 10-microgram shots - one-third of the dose given to adults and teens.

Five- to 11-year-olds are now eligible for Pfizer's COVID-19 vaccine, following a unanimous vote by a Centers for Disease Control and Prevention advisory committee and a nod from CDC Director Dr. Rochelle Walensky on Tuesday.

In clinical trials, the Pfizer vaccine was found to be 91% effective at reducing the risk of symptomatic illness in children in that age group.

There are key differences, though, between the vaccine 5- to 11-year-olds will receive and the Pfizer shots given to adults and teenagers. Here's what parents may want to know about the needles, doses, and side effects now that the shot is available.

Smaller needles, a lower dose, fewer side effects, same benefit

The vaccine rollout looks different for kids than it did for adults.

Instead of the mass vaccination sites adults flocked to, pediatricians will be heavily involved in administering vaccines to kids, according to the White House. Doctors and nurses will also use smaller needles on kids than on adults.

Additionally, although the kids' vaccine still involves two shots spaced three weeks apart, 5- to 11-year-olds will get smaller doses. Adults and teenagers got 30-microgram doses, whereas younger kids will receive just 10 micrograms.

That lower dose is just as effective for young children as a higher dose would be, according to Dr. Simon Li, a principal investigator helping run the vaccine study on kids in New Jersey alongside Pfizer.

"The dose decision-making was really smart," Li, who's also an associate professor of pediatrics at Rutgers, told Insider.

Pfizer tested the vaccine on kids at 30 micrograms and at 10 micrograms and found that the two versions produced a similar amount of antibodies in that age group. But kids experienced more side effects - such as pain, tenderness, redness, fever, chills, and fatigue - with the 30-microgram dose.

Li said he hopes that hearing the vaccine was specifically designed to have fewer side effects for kids will alleviate parental stress. His own kids are 4, 8, and 10, and he's impatient to get them the shots.

"Once it's available, I would 100% get them vaccinated," Li said. "Hopefully they can be first in line."

Pfizer's clinical trial for 5- to 11-year-olds included 2,268 participants. Of that group, 19 kids tested positive for COVID-19, 16 of whom had received placebo shots and three of whom were in the vaccinated group. There were no severe COVID-19 cases or deaths in either cohort. The most common side effects from the shot were pain at the injection site, fatigue, and headache.

Pfizer reported five serious adverse events during the course of the trial, but none was linked to the vaccine. Rather, the five events serve as both a reminder of the detailed monitoring in clinical trials and also of how young the participants are. In addition to reporting bone fractures and an arthritic infection among the kids in its trial, Pfizer also noted that one child swallowed a penny.

Federal advisors question whether the shot is necessary for all kids

Last week, the Food and Drug Administration's advisory panel voted 17-1 in favor of authorizing Pfizer's vaccine for kids (one member abstained) and the FDA subsequently authorized the shot for emergency use in children. Still, a few panel members expressed skepticism about the wide-reaching recommendation.

"I do believe children at high risk do need to be vaccinated," Dr. James Hildreth, a panelist and president of Meharry Medical College, said. "But vaccinating all of the children to achieve that does seem a bit much for me."

Another panelist, Dr. Eric Rubin, the editor-in-chief of The New England Journal of Medicine, weighed the risk of myocarditis, or heart inflammation, in his decision. But ultimately, he and other panelists agreed that the vaccine's benefits outweigh the risk of that and other potential rare side effects.

Dr. Andrew Pavia, a pediatric infectious disease specialist at the University of Utah who was not on the panel, sees it differently.

"Delta has made COVID a pediatric problem," Pavia told Insider in October. "They've often heard that because kids don't die at the rates that adults do, that it's not a big deal. And that was sort of true in 2020. With Delta, it's not true."

Andrew Dunn and Hilary Brueck contributed reporting.