The Food and Drug Administration approved COVID-19 vaccine doses for the fall and winter season on Wednesday — but with limitations that will likely hinder access for millions of people.

The agency granted approval for COVID-19 vaccine doses for people over age 65, who are most vulnerable to severe infections, but younger people will only be eligible if they have at least one underlying medical condition that puts them at higher risk for hospitalization or death. Younger people without such conditions could have trouble getting the shot.