As @aygart said, analogies are straw man arguements, there are many differences between coronavirus and the flu.
Regardless, if getting it doesnt mean immunity then there can't be a vaccine and this will last forever. Lockdown can just end today because nothing can ever change.
Yet you’re making a straw man in the very same post. JUST LIKE THE FLU, one can presumably be exposed yet not automatically become infected. JUST LIKE THE FLU, that does NOT mean there can’t be immunity and a vaccine. Again, things are not black and white like that. Here is your reasoning.
Someone was exposed to the virus.
If they didn’t already get it, they must be immune.
Otherwise, there must be no such thing as immunity, so a vaccine can never be made, so let’s end the lockdown immediately.
Does that logic work?