Background: Mitochondrial dysfunction and redox cellular imbalance indicate crucial function in COVID-19 pathogenesis. Since 11 March 2020, a global pandemic, health crisis and economic disruption has been caused by SARS-CoV-2 virus. Vaccination is considered one of the most effective strategies for preventing viral infection. We tested the hypothesis that preventive vaccination affects the reduced bioenergetics of platelet mitochondria and the biosynthesis of endogenous coenzyme Q10 (CoQ10) in patients with post-acute COVID-19. Material and Methods: 10 vaccinated patients with post-acute COVID-19 (V + PAC19) and 10 unvaccinated patients with post-acute COVID-19 (PAC19) were included in the study. The control group (C) consisted of 16 healthy volunteers. Platelet mitochondrial bioenergy function was determined with HRR method. CoQ10, γ-tocopherol, α-tocopherol and β-carotene were determined by HPLC, TBARS (thiobarbituric acid reactive substances) were determined spectrophotometrically. Results: Vaccination protected platelet mitochondrial bioenergy function but not endogenous CoQ10 levels, in patients with post-acute COVID-19. Conclusions: Vaccination against SARS-CoV-2 virus infection prevented the reduction of platelet mitochondrial respiration and energy production. The mechanism of suppression of CoQ10 levels by SARS-CoV-2 virus is not fully known. Methods for the determination of CoQ10 and HRR can be used for monitoring of mitochondrial bioenergetics and targeted therapy of patients with post-acute COVID-19.