"However, whether reinfection adds to the risk incurred after the first infection is not clear."

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) …”

Hate to be that guy, but people who are susceptible to reinfection are also probably less healthy.

I'm pretty sure everyone is susceptible to reinfection after a while.

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.

Affirmative. (biochemist)