WASHINGTON, Oct 22 (Reuters) - Biden administration officials urged eligible Americans on Friday to get booster shots of a COVID-19 vaccine and the Centers for Disease Control and Prevention head said it may update its definition of what constitutes full vaccination. Currently people in the United States are considered fully vaccinated if they have had two doses of the Pfizer/BioNTech or Moderna Inc vaccine, or one dose of the vaccine made by Johnson & Johnson. "We have not yet changed the definition of "fully vaccinated." We will continue to look at this. We may need to update our definition of "fully vaccinated" in the future," CDC director Rochelle Walensky told reporters. "If you"re eligible for a booster, go ahead and get your booster and we will continue to follow," she said.