Can surviving giardiasis lessens or eliminates the possibility of getting it again?

Yes and no: Host immunity plays a role in elimination of giardia and provides some protection against infection on re-challenge. Partial protective immunity can develop. This is supported by epidemiologic studies of human giardiasis. Reinfection is common especially in children in endemic settings. Reinfection can be due to infectiion with different genotypes of the organism.

Possibly lessen: Infection with Giardia cause the immune system to develop anti-parasite IgA. Reinfections can lead to reduced symtpoms but does not prevents Giardia from colonizing & producing cysts.