//My patient caught Covid-19 twice. So long to herd immunity hopes.

My patient caught Covid-19 twice. So long to herd immunity hopes.

Medical staff from myCovidMD provide free Covid-19 antibody testing in Inglewood, California on June 19, 2020. The unknowns of immune responses to the coronavirus currently outweigh the knowns. | Mark Ralston/AFP via Getty Images

Emerging cases of Covid-19 reinfection suggest herd immunity is wishful thinking.

“Wait. I can catch Covid twice?” my 50-year-old patient asked in disbelief. It was the beginning of July, and he had just tested positive for SARS-CoV-2, the virus that causes Covid-19, for a second time — three months after a previous infection.

While there’s still much we don’t understand about immunity to this new illness, a small but growing number of cases like his suggest the answer is “yes.”

Covid-19 may also be much worse the second time around. During his first infection, my patient experienced a mild cough and sore throat. His second infection, in contrast,