I didn't read the underlying papers, only the linked article so please take this with a grain of salt. Serology has not been correlated with patient outcomes.

I didn't read the underlying papers, only the linked article so please take this with a grain of salt. Serology has not been correlated with patient outcomes. The threshold for "success" may be much lower than what is even measurable by the lab (just as an example). Vaccines tend to produce much higher measurable antibodies than infection but we also know that infection is pretty effective at preventing repeat hospitalization. I believe this study is simply putting a microscope on the effectiveness of infection by magnifying the initial immune response with the vaccine. Put another way, I'm not yet convinced this study should be used to suggest vaccination for those prior infected because we don't yet know the threshold for success.