I think my internal definition is just fine thanks. Immunity implies that the host body has developed antibodies to neutralize viral replication or interferons

I think my internal definition is just fine thanks. Immunity implies that the host body has developed antibodies to neutralize viral replication or interferons which straight up kill viruses. As a result, the presence of the virus is reduced, possibly to near zero. But that's not really the case here. You might be asymptomatic but still shedding virus just as much as someone on their deathbed. With respect to children, they still become infected at the same rate. They still provide a place for viral replication even if they are asymptomatic.