That's news to me, I seem to remember news stories from last year that people were being infected multiple times and the immunity from having endured COVID-19 was not actually that good. Quickly trying to look this up with 'covid-19 reinfection' as query (trying to avoid confirmation bias in that search), the top hit on DDG is the USA CDC which writes:

> Among Kentucky residents infected with SARS-CoV-2 in 2020, vaccination status of those reinfected during May–June 2021 was compared with that of residents who were not reinfected. In this case-control study, being unvaccinated was associated with 2.34 times the odds of reinfection compared with being fully vaccinated. --https://www.cdc.gov/mmwr/volumes/70/wr/mm7032e1.htm

Reinfection occurs much more frequently if you don't get vaccinated, if I am reading this right. Not sure I'd call "natural" immunity "also" or "incredibly" effective.