California Gov. Gavin Newsom said Tuesday that it is "unlikely" sports with fans in attendance will return this summer because of the coronavirus pandemic.
"The prospect of mass gatherings is negligible at best until we get to herd immunity and get to a vaccine," Newsom said.
While there are multiple vaccines in the works, it's unlikely one will be approved any sooner than a year from now. Herd immunity happens when there are so many people immune to a particular infectious disease—in most cases because they previously had it—that it slows or stops the spread.
People who have tested positive for COVID-19 a second time after previously recovering from the disease have caused some doubts that this virus could be slowed by herd immunity.
Newsom also outlined what must happen for California to end its stay-at-home order:
Nearly all major sports leagues have indefinitely postponed operations because of the pandemic. Most are exploring their potential options for continuing their respective seasons without fans in attendance, though all have maintained they will act at the behest of public health officials.
There have been nearly 600,000 confirmed cases of coronavirus in the United States, the most of any country in the world. There have been 25,191 confirmed deaths as of Tuesday.
California has been among the most aggressive states enacting and enforcing stay-at-home orders for non-essential business and travel. Newsom's actions have led to some level of success, with California currently sitting under 25,000 cases despite having the largest population of any state.