The Biden administration is expected as soon as this week to authorize a fourth dose of either the Pfizer or Moderna COVID-19 vaccine to people ages 50 and older, according to reports published over the weekend. In this file photo from Sept. 18, 2021, Steve Cancino, right, receives his second dose of the Moderna COVID-19 vaccine from registered nurse Jessica Johnson during a pop-up vaccination clinic. (Erik Verduzco / Las Vegas Review-Journal) @Erik_Verduzco