The Pfizer COVID-19 vaccine is nearly 91% effective against symptomatic illness in children ages 5-11, according to new data posted Friday ahead of a major FDA advisory committee meeting on Tuesday.

The vaccine also appeared safe, with none of the children experiencing a rare heart inflammation side effect known as myocarditis. If authorized in children 5-11, the Pfizer vaccine will be given at a smaller, one-third dose.

This efficacy estimate is from the company's clinical trial of 2,268 children in which some children got a placebo, and some children got the Pfizer vaccine. During the trial, 16 children who got the placebo shots developed COVID-19. Only three children who got the real vaccine developed COVID-19.

A small number of the children who were vaccinated and later developed COVID-19 experienced symptoms far fewer and milder than the children who were unvaccinated. For example, none of the vaccinated children developed a fever, while a majority of the unvaccinated children developed a fever along with other symptoms.

None of the children experienced serious adverse events. Many experienced typical symptoms like pain at the injection site, fatigue and headache.

The FDA's advisers will meet Tuesday to vote on whether to authorize the vaccine. From there, the FDA itself and the CDC will need to sign off -- a process that can take several days -- before shots could become available to children nationally.

- ABC News' Sony Salzman

Hours after the unanimous vote from its independent advisory committee, the Centers for Disease Control and Prevention has signed off on recommending booster shots for the Moderna and Johnson & Johnson COVID-19 vaccines for certain populations.

CDC Director Rochelle Walensky recommended boosters for Pfizer and Moderna recipients with no preference on the brand, leaving that decision up to the individual.

People who are 65 and older, or individuals as young as 18 who have underlying medical conditions or live in high-risk or long-term care settings, are eligible to receive either a Pfizer or Moderna booster at least six months after their second shot, the CDC said.

The one-shot Johnson & Johnson vaccine is eligible to anyone aged 18 and up, at least two months after their initial dose, the CDC said.

-ABC News' Eric Strauss

An independent Centers for Disease Control and Prevention advisory committee voted unanimously Thursday evening to recommend booster shots for both the Moderna and Johnson & Johnson COVID-19 vaccines for certain populations.

The panel recommended a third dose of the Moderna vaccine at least six months after a person’s initial course for those 65 and older, as well as those as young as 18 who are at higher risk due to underlying health conditions or where they work or live.

A second dose of the one-shot Johnson & Johnson vaccine was recommended for anyone aged 18 and older, at least two months after the first dose.

The panel also cleared the way for allowing mixing and matching of booster doses.

The recommendations fall in line with the Food and Drug Administration’s authorization of the boosters Wednesday.

CDC Director Rochelle Walensky must now sign off on the panel's recommendations. A decision is expected within a day.

-ABC News' Sasha Pezenik

COVID-19 hospital admissions in the U.S. have dropped by about 9.7% in the last week, according to federal data.

Death rates are also falling, though they remain persistently high, with an average of just under 1,250 Americans dying from the virus each day, according to the data.

Alaska currently has the country's highest infection rate, followed by Montana, Wyoming, Idaho and North Dakota.

The U.S. is currently averaging around 76,000 new cases per day, down from 160,000 in early September. Despite boasting high vaccination rates, several Northern states continue to see cases tick up as the weather gets colder.

-ABC News' Arielle Mitropoulos