https://www.newscientist.com/article...dont-know-yet/
SARS-CoV-2 does not appear to be mutating -
there are currently just two almost identical strains of it, therefore it is not unreasonable to believe that we can build an immune response to it, however there is no concrete evidence either way yet according to that article (25th March). Also, antibody responses to other types of coronavirus are fairly short term which may also apply to this one.
Flu mutates rapidly hence why there is a new variant and a new vaccine every year. If SARS-CoV-2 does that we're in a bit of a pickle...