Nelson was poised to attend an event at the Space Telescope Science Institute in Baltimore, Maryland, ahead of the July 12 release of the new James Webb Space Telescope's first images of the cosmos.
"I wish I could be there, but I tested positive for COVID last night," Nelson remotely told reporters during a news conference.
Nelson, 79, was vaccinated and boosted against the coronavirus and is experiencing mild symptoms, his press secretary told Reuters.
(Reporting by Joey Roulette; Editing by Bill Berkrot)
By Joey Roulette