Please note that the control group(those presumed infected by other strains) and Omicron group differed dramatically.  Participation rates were low in both cohorts.  Information was gathered over the phone for one and through the mail for the other.  Absolute numbers of participants were low in both groups.  Many patients were already vaccinated before breakthrough Omicron infection, which reduces the incidence of long COVID.  I'll spare you more commentary.

I also can't find Appendix 1, which is the questionnaire.

This is of vital importance to the global economy, so I really, really hope this receives more study.