What are the next steps as a F.D.A. panel considers Moderna and Pfizer vaccines for very young children?

An independent panel of experts advising the Food and Drug Administration is scheduled to vote on Wednesday on whether to recommend to the agency that very young children be allowed to receive shots of the Moderna and Pfizer-BioNTech coronavirus vaccines.

But that’s just one step in a process regulators must follow before the vaccines could become available to children as young as 6 months old.

The F.D.A., Centers for Disease Control and Prevention and the states have more to do before the Moderna vaccine would be available to children through age 5 and the Pfizer shot would be available to children through age 4.

In a similar process, the expert panel recommended on Tuesday that the agency authorize the Moderna vaccine for older children and adolescents.

Both the F.D.A. and the Centers for Disease Control and Prevention will prioritize decisions on vaccines for the youngest children over Moderna shots for older youths and teenagers because of the unmet need, officials familiar with the planning said.

Here are the next steps.

The F.D.A.

• As the agency within the Department of Health and Human Services that supervises medications and related matters, the F.D.A. will consider the advisory panel’s recommendation. The agency usually follows the advisory panel’s advice, but it is free to make changes or reject the recommendation outright.

• Once the F.D.A. completes its review, it issues a determination.

The C.D.C.

• If the F.D.A. authorizes the vaccines, another advisory panel, this one set up by the C.D.C., will review that decision and vote on whether to recommend the pediatric vaccines.

• The C.D.C. then takes up that panel’s recommendations, and the agency’s director, Dr. Rochelle P. Walensky, issues the agency’s guidance on whether the vaccines should be made available to the very young children.

• Similar to the F.D.A., the C.D.C. usually follows the nonbinding recommendations of its advisory committee. But it has not always gone that way: Last September, after the C.D.C. panel rejected the F.D.A.’s recommendation that frontline workers be included among those eligible for a Pfizer-BioNTech booster, Dr. Walensky overrode her own agency’s advisers and agreed with the F.D.A.

State agencies and providers

The agency’s guidance is deeply influential for states, doctors, pharmacies and other health care institutions and the general public. State health departments generally follow the guidance, but can set their own rules.

The timeline

Once the F.D.A.’s advisory committee issues its recommendation, the process can move quickly. Already, the Biden administration has been preparing for the possibility that the two vaccines will win speedy authorization for use in young children and has set a goal of the first shots being given the week of June 19. Already, the administration is taking advance orders from the states for 10 million pediatric doses, split equally between the Moderna and Pfizer-BioNTech vaccines.