CNBC’s Jim Cramer delivered an optimistic tune on Monday, predicting that the reopening plays will surge again when the U.S. reaches herd immunity against Covid-19.

“If we reach some sort of nationwide pseudo herd immunity through a combination of vaccines and infections, or even if we just get a peak in new cases, it could be like a second reopening for the travel, leisure, retail, industrials and energy stocks,” the “Mad Money” host said.

“Once we start getting over this new outbreak, they’ll be the place to invest,” Cramer said, though he did not offer any stock recommendations.

Cramer credited Dr. Scott Gottlieb with helping to spark buying in stocks on Monday. Using the U.K. as an indicator, the Pfizer board member and former U.S. Food and Drug Administration chief told CNBC that he expects delta transmissions in America to peak within a month.

The comments made Cramer more positive on the health outlook.

“When Covid burns itself out, you’ll want to own exactly the kind of stocks that you’d be selling if you’re worried about the nightmare scenario, which is why this market just refuses to stay down,” Cramer said.

Though Cramer is bullish on reopening plays, the market is still facing a number of threats, including rising Covid cases in the U.S. driven by the highly contagious delta variant and ongoing inflation. Cramer also included infrastructure negotiations in Washington, concerns about the debt ceiling and geopolitical issues with China as other major risks in a “nightmare scenario.”

Disclosure: Scott Gottlieb is a CNBC contributor and is a member of the boards of Pfizer, genetic testing start-up Tempus, health-care tech company Aetion Inc. and biotech company Illumina. He also serves as co-chair of Norwegian Cruise Line Holdings’ and Royal Caribbean’s “Healthy Sail Panel.”