The Centers for Disease Control and Prevention have now signed off on boosters for all three COVID-19 vaccines authorized in the U.S., after Thursday's recommendation for the Moderna and Johnson & Johnson shots.

Unsure if you're eligible to receive any of them? Check out ABC News' handy guide.

A new report from the Centers for Disease Control and Prevention suggests that although the delta variant is significantly more transmissible than prior variants, it is not more likely to lead to hospitalization.

Instead, the dramatic uptick in hospitalizations seen during the summer's delta surge was fueled by the highly transmissible variant spreading easily among mostly unvaccinated people, the CDC said. 

The report, which analyzed COVID-19 hospitalization data from 14 states, also found that the proportion of people aged 18 to 49 hospitalized with delta increased "significantly" in July and August to 35.8% of all hospitalizations compared to 24.7% from January to June of this year. This was likely due to lower vaccination rates among younger people, the CDC said.

-ABC News' Sony Salzman

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

The U.S. vaccination initiation average is at one of its lowest points since the introduction of vaccines nearly 10 months ago, according to federal data. Just over 182,000 Americans are receiving their first dose each day, while roughly 335,000 Americans are receiving a booster shot each day.

More than 112.5 million Americans remain unvaccinated and about 64.3 million of the unvaccinated are over the age of 12, and thus currently eligible for a shot, according to federal data. 

The FDA authorized boosters for Moderna and J&J late Wednesday. The Moderna booster is authorized for adults 65 and older and those at high-risk. The J&J booster is authorized for adults at least two months after their primary vaccination.

The FDA said it's OK to mix a booster but did not say any booster combination was preferred over another.

-ABC News' Sony Salzman, Arielle Mitropoulos