The sentence you’ve quoted, from the abstract of the paper, refers to the state of knowledge before this paper was written/published.
The results section of the paper updates this knowledge. It says:
“Compared to those with first infection, those with reinfection exhibited increased risk and excess burden of all-cause mortality, hospitalization, and at least one sequela in the acute phase and the post-acute phase of the reinfection.”
“… the risk was higher in those who had two infections (HR 2.11 (2.07, 2.15); burden 234.58 (227.08, 241.92)), and highest in those with three or more infections (HR 3.00 (2.71, 3.31) …”
Susceptibility is also a spectrum, though, which is what I meant to get at and failed to communicate clearly. Immunocompromised people are probably more susceptible than others? I don't have data on that, it's just a guess.