This is a complex area as the characteristics of long Covid can be seen in an individual who has only been vaccinated.
Additionally, some have improvement or worsening of symptoms after vaccination.
This is an outlier pattern and has to be explain thoroughly in order to have a full understanding of long Covid.
Rohrhofer, Johanna, et al. "Association between Epstein-Barr-Virus reactivation and development of Long-COVID fatigue." Allergy (2022).
Fatigue in long Covid and Epstein Barr reactivation