• A key CDC advisory panel is scheduled to vote Wednesday on whether to recommend the Pfizer-BioNTech Covid vaccine's use for kids ages 12 to 15.
• States could begin administering shots in adolescents on Thursday, pending an endorsement from the CDC's Advisory Committee on Immunization Practices.

A key CDC advisory panel is scheduled to vote Wednesday on whether to recommend expanding usage of Pfizer's and BioNTech's Covid-19 vaccine to kids ages 12 to 15.

The endorsement from CDC's Advisory Committee on Immunization Practices, which is widely expected, is the last step before U.S. officials give states the thumbs up to open vaccinations to millions of adolescents as early as Thursday.

Allowing adolescents to get the shots will accelerate the nation's efforts to drive down infections and return to some form of normalcy, public health officials and infectious disease experts say. It also allows states to get middle school students vaccinated before summer camps begin and school starts in the fall.

The Centers for Disease Control and Prevention panel's meeting comes two days after the Food and Drug Administration announced it approved Pfizer and BioNTech's request to allow their vaccine to be given to young teens on an emergency use basis. The vaccine is already authorized for use in people 16 and older. It will be administered in adolescents in two doses, three weeks apart, the same regimen for 16 years of age and older, the FDA said.

Here's what to expect.

When are they voting?

The meeting is scheduled to run from 11 a.m. ET to 5 p.m. ET, according to a draft of the agenda. The vote typically happens toward the end.

Before the vote, medical experts will assess Pfizer and BioNTech's clinical trial data and offer their opinions on the vaccine, including whether the benefits outweigh the risks for use in adolescents. The companies said in late March that the vaccine was found to be 100% effective in a clinical trial of more than 2,000 adolescents. Side effects were generally consistent with those seen in adults, they added.

What happens next?

Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, told reporters on Monday that he expected the first shots for young teens to be administered as soon as Thursday, pending the panel's endorsement and approval from the CDC director.

Vaccine distribution will vary in the U.S., officials told reporters, because states have different regulations on who can administer shots to younger age groups. The Biden administration has said it plans to send vaccines directly to pediatricians' offices and make doses available at other sites like community centers.

Is the vaccine safe?

In a statement Monday, acting FDA Commissioner Dr. Janet Woodcock assured parents that the agency "undertook a rigorous and thorough review of all available data" before clearing it for use in younger teens.

The FDA said side effects in adolescents were consistent with those reported in clinical trial participants who were 16 and older. It noted the vaccine should not be given to anyone with a known history of severe allergic reactions, including anaphylaxis, a severe and potentially life-threatening allergic reaction.

The most commonly reported side effects were pain at the injection site and in joints and muscles, tiredness, headache, chills and fever, according to the FDA. With the exception of pain at the injection site, more adolescents reported side effects after the second dose than after the first, the agency said. Side effects generally lasted one to three days.

When will younger kids get access?

Trials are underway testing Covid vaccines in kids under age 12, but researchers expect those trials to take longer because they are gradually studying younger age groups and experimenting with lower doses after the vaccines prove to be safe in older kids.

Approval by the FDA for kids under age 12 could come in the second half of this year. In a slide presentation that accompanied the company's earnings release on May 4, Pfizer said it expects to apply for authorization for its vaccine for use in toddlers and young children in September and infants in November.

Moderna and Johnson & Johnson, whose vaccines are authorized for people 18 and older, are also testing their shots in younger age groups.

Will kids need shots for school and activities?

Possibly. Schools, for example, can legally require students to get vaccinated, according to Dorit Reiss, a law professor at UC Hastings College of Law.

Several colleges and universities have already said they are requiring Covid vaccinations for students returning in the fall. It is possible vaccinations will be required to participate in after-school extracurricular activities such as sports, art and other in-person activities.

It's unlikely the federal government will mandate vaccines for kids or any other group, public health experts say.

The CDC has already said schools can safely reopen without vaccinating teachers or students. The Biden administration has said it would pour $10 billion into Covid testing for schools in an effort to hasten the return to in-person classes across the country this fall.