Inclusion Criteria:
1. An adult aged ≥18 to ≤65 years at the time of Screening with a BMI \<50.0 kg/m2.
2. Long-COVID (LC) Cohort: acute SARS-CoV-2 infection prior to onset of Long-COVID symptoms resulting in diagnosis of Long-COVID.
Post-Vaccination Syndrome (PVS) Cohort: Administered at least a single dose of a SARS-CoV-2 vaccine prior to the onset of symptoms resulting in diagnosis of PVS.
3\. Clinical evidence of at least 2 new or worsening LC or PVS symptoms with at least 1 symptom considered grade 3 or greater in severity which: (i) LC Cohort - presented between 6 and 24 months after inciting acute COVID-19 infection.
(ii) PVS Cohort - presented and persisted after administration of a COVID-19 vaccine.
(iii) are not primarily attributable to a pre-existing condition or alternative diagnosis confirmed by the investigator during screening: chest pain, diarrhea, abdominal pain, nausea, loss of smell or taste, palpitations, shortness of breath, cough, sleep apnea, swelling of legs, weakness, muscle pain, joint pain, back pain, foot pain, abnormal movements, tremor, headache, sleep disturbance, difficulty with memory/concentration ("brain fog"), fatigue, post-exertional malaise.
Exclusion Criteria:
1. Has had an unplanned hospitalization or had major surgery (e.g., requiring general anesthesia or opening of a major body cavity) within 3 months of Screening or has a planned hospitalization or major surgery during the study period.
2. Has any pre-existing disease, condition, or disorder that is associated with symptoms that overlap or could confound the evaluation of LC or PVS (e.g., fatigue, pain, cognitive impairment, dysautonomia, exercise intolerance), including but not limited to, myalgic encephalomyelitis/chronic fatigue syndrome, post-treatment Lyme disease, fibromyalgia, autonomic disorders (e.g., postural orthostatic tachycardia syndrome), disorders affecting cognitive function, primary sleep disorders, or other conditions that, in the opinion of the Investigator, could confound the results obtained from clinical activity evaluations.
3. Has any current serious concomitant systemic disease, condition, or disorder that, in the opinion of the Investigator, may lead to new treatments, hospitalization, or death within the study period, including but not limited to, active malignancy, organ failure, recent cardiovascular disease or stroke, uncontrolled diabetes, major psychiatric disorders, that could confound the results of the study or confer an additional risk to the participant by their participation in the study.
4. Has moderate to severe immune compromise due to a medical condition or immunosuppressing medications.
5. Has known active Hepatitis B (HBV) or Hepatitis C (HCV) infection or known human immunodeficiency virus (HIV) infection with a currently detectable viral load, current HIV-related symptoms, or an unstable antiretroviral regimen (initiated or changed within the past 3 months prior to Screening).
6. Has received a COVID-19 vaccine within 60 days before Screening or planned receipt during the study period, or any non-COVID-19 vaccine within 14 days before Screening or within 7 days before or after each study dose. Note: Vaccination during the study period should be avoided unless medically indicated, such as a seasonal vaccine or if the vaccine cannot be deferred until after the study.
7. Has been treated with or anticipates being treated during the study period with any of the following medications:
1. A mAb with activity against SARS-CoV-2 within 12 months before Screening.
2. An antiviral with activity against SARS-CoV-2 within 30 days before Screening.
3. Convalescent plasma or intravenous immunoglobulin (IVIg) within 60 days before Screening.
4. Systemic corticosteroids at doses \>20 mg per day of prednisolone or equivalent for \>14 consecutive days within 30 days before Screening.
5. Other systemic immunosuppressive medications, such as biologics, immunomodulators, or cancer chemotherapy, within 90 days before Screening. Note: Topical, inhaled, intranasal, ophthalmic, or locally injected corticosteroids or other immunosuppressants are permitted, provided there is no evidence of clinically meaningful systemic immunosuppressive effect.
NOTE: The above information is not intended to contain all considerations relevant to a participant's potential eligibility in the clinical trial.
