ABVN	Auricular branch of the vagus nerve
ARAS	Ascending reticular activating system
BFI	Brief Fatigue Inventory
CAP	Cholinergic anti-inflammatory pathway
CENTRAL	Cochrane Central Register of Controlled Trials
CI	Confidence interval
FSS	Fatigue Severity Scale
GAD-7	Generalized Anxiety Disorder-7 scale
GRADE	Grading of Recommendations, Assessment, Development and Evaluations
HRV	Heart rate variability
JADAD	Jadad quality assessment scale
LC	Locus coeruleus
LF/HF	Low-frequency/high-frequency (HRV ratio)
NTS	Nucleus tractus solitarius
PASC	Post-acute sequelae of SARS-CoV-2
PCC	Post-COVID-19 condition
PCFS	Post-COVID-19 Functional Status scale
PEDro	Physiotherapy Evidence Database scale
PHQ-9	Patient Health Questionnaire-9
PRISMA	Preferred Reporting Items for Systematic Reviews and Meta-Analyses
PROSPERO	International Prospective Register of Systematic Reviews
RCT	Randomized controlled trial
RMSSD	Root mean square of successive differences (HRV parameter)
RoB 2	Cochrane Risk of Bias 2 tool
SARS-CoV-2	Severe acute respiratory syndrome coronavirus 2
SDNN	Standard deviation of normal-to-normal intervals (HRV parameter)
SWiM	Synthesis Without Meta-Analysis
taVNS	Transcutaneous auricular vagus nerve stimulation
VNS	Vagus nerve stimulation