[...] Those with powerful natural immunity may be protected from reinfection for up to a year. But even they should not skip the vaccine, experts said. For starters, boosting their immunity with a vaccine is likely to give them long-lasting protection against all the variants.
“If you’ve gotten the infection and then you’ve been vaccinated, you’ve got superpowers,” said Jennifer Gommerman, an immunologist at the University of Toronto.
Without that boost, antibodies from an infection will wane, leaving Covid-recovered people vulnerable to reinfection and mild illness with variants — and perhaps liable to spread the virus to others.
This is the same argument for giving boosters to people who are fully vaccinated, said Michel Nussenzweig, an immunologist at Rockefeller University in New York. “After a certain period of time, you’re either going to get boosted or you’re going to get infected,” he said.
How immunity from infection and from vaccination compare is difficult to parse. Dozens of studies have delved into the debate, and have drawn contradictory conclusions. [...]
There are a lot more details in the article, it's worth reading the whole thing.