Is it true that there are people who are naturally immune or greatly resistant to the norovirus?

Maybe, but probably not. However, people with prior norovirus infections often are less susceptible or entirely immune to repeat infections. Many norovirus infections cause no symptoms; even without a known prior illness, some people are resistant.

Immunity to a specific strain of this highly contagious virus occurs, but there are many strains. You have to execrcise a high standard of personal cleanliness to prevent contraction. This artical from the CDC will help you understand: https://www.cdc.gov/norovirus/index.html#:~:text=Norovirus%20is%20a%20very%20contagious,Consuming%20contaminated%20food%20or%20water