PAX is a prospective, randomized (1:1), double-blind, placebo-controlled study, that have as a objective to evaluate the safety and tolerability of plasma exchange (PE) in patients with Post Acute Covid-19 Syndrome (PCC) comparing to sham plasma exchange. The participants will be randomized in two arms: (1) 6 sessions of PE (Plasma Exchange) with human serum albumin 5% or (2) 6 sessions with placebo (infusion of of sterile saline solution 0.9%) on days 1, 3, 8, 10, 15 and 17.

Randomized participants will receive plasma exchange (PE) or sham PE (placebo) (6 sessions: V2, V3, V4, V5, V6 and V7) and will continue their follow-up visits(V8d22, V9d45, V10d90). Plasma volumes will be replaced, which will vary depending on sex, height, weight and hematocrit.

Inclusion Criteria:

1. Male or female individuals 18 years-old or older.
2. Evidence of previous SARS-CoV-2 infection at least 90 days prior to study recruitment, defined by either (a) Nasopharyngeal SARS-CoV-2 nucleic acid test (Polymerase chain reaction [PCR] or Transcription-Mediated Amplification [TMA] (b) validated Nasopharyngeal Lateral Flow Assay rapid antigen test [RAT], or (c) SARSCoV-2 serology before SARS-CoV-2 vaccination.
3. Symptoms of PCC after 90 days of infection and that last for at least 2 months and cannot explained by an alternative diagnosis.
4. Not able to perform all usual duties/ activities due to symptoms, pain, depression or anxiety, defined as grades 3 or 4 in the post-COVID-19 Functional Status (PCFS) scale.
5. Availability of an adequate peripheral venous cannulation.
6. If women of childbearing potential, use of a highly effective method of contraception (abstinence, hormonal contraception, intra-uterine device [IUD], or anatomical sterility in self).
7. Willing to comply with the requirements of the protocol and available for followup for the planned duration of the study.
8. Has understood the information provided and capable of giving informed consent. Exclusion criteria

Exclusion Criteria:

1. SARS-CoV-2 infection diagnosed during the previous 90 days.
2. Last SARS-CoV-2 vaccine dose during the previous 30 days.
3. No significant limitations in the subject's ability to perform all usual duties/activities (i.e., grades 0, 1 or 2 in PCFS scale).
4. Medical conditions for which 250 mL of intravenous fluid is considered dangerous (i.e., decompensated heart failure or renal failure with fluid overload, among others).
5. Pregnant or breastfeeding women.
6. Contraindications for therapeutic PE: Non-availability of an adequate peripheral venous catheter, hemodynamic instability, septicemia, known allergy to fresh frozen plasma or replacement colloid/albumin, known allergy to heparin.
7. Current or planned hospital admission for any cause during the study follow-up.
8. Inability to consent and/or comply with study requirements, in the opinion of the investigator.
9. Currently participating or planning to participate in any other clinical trial until day 90 of follow-up.

This will be a double blind, placebo-controlled study. Masking of investigational products will ensure that both the investigator and the participant are blinded to the type of exchange procedure. Patients will be unable to distinguish true from sham procedures at the end of the study. Each procedure will take approximately 2 hours to complete. In the sham procedure, the patients will also underwear 6 procedures lasting approximately 2 hours each. Blinding will be maintained throughout the study until after 3-month follow-up assessment of the last patient exchanged