The number of Americans who are not immunocompromised but have obtained extra shots is unclear. About 1.8 million people have done so since mid-August, according to the Centers for Disease Control and Prevention, but that count is likely to include many with weakened immune systems. The Food and Drug Administration authorized additional shots for that group last month…

“Frankly, I did not trust the government to act on the science,” said Lynn Hensley, who assigned herself a booster in July, six months after her second shot. “I’m 78 and consider myself at a greater risk. I feel like I can just read what’s out there and make up my own mind.”

She went to a temporary county vaccine clinic in the Fox River Valley area of Wisconsin.

“They did ask me if it was my first or second shot, and I told them it was my first,” she said. “I did feel bad about it. But I didn’t feel bad enough.”