Investigators performed a cross-sectional analysis (May/June 2022) within a prospective multicenter Swiss healthcare worker (HCW) cohort (n=2,912) of predominantly young, healthy Caucasian females. Uninfected HCWs served as controls.  Previous infection during pre-Omicron BA-1 variant waves (Wild-type n=283 + Alpha/Delta n=268) was the strongest risk factor for post-acute COVID symptoms >4 weeks after infection, and lasting more than 7 days, when compared with those infected during the Omicron BA.1 wave (n=963) or no infection (n=1056). Eighteen symptoms as well as indices of depression and anxiety were assessed. Long Covid was diagnosed in 17% of those infected during the initial wave, 10% of those during Alpha/Delta and 5% of those during Omicron BA-1.  The number of acute infection symptoms also decreased and was associated with the number of PASC symptoms. Those infected during the Omicron BA.1 wave had no additional protective effect from prior vaccination although the proportion of those unvaccinated was only 9%.

https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciad143/7076063