The COVID-19 pandemic has swept across the globe, affecting millions of individuals with varying degrees of severity. While many individuals recover from the acute phase of the infection, a significant proportion continue to experience persistent and debilitating symptoms long after the initial SARS-CoV-2 infection. This condition, known as Long COVID (LC) or sometimes referred to as Post-COVID Condition (PCC) or post-acute sequelae of COVID-19, has emerged as a complex multisystemic condition and challenging health issue, affecting approximately 10% of COVID-19 patients. Various symptoms characterize LC, including fatigue, sleep disturbances, cognitive impairment, and mood disturbances. Some of the symptoms are shared with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) - a condition marked by debilitating fatigue and a host of other symptoms without precise biomarkers or objective tests for diagnosis. Effective LC treatments remain elusive and LC patients continue to grapple with persistent symptoms that significantly impact their quality of life. Given the lack of effective treatments, it is imperative to explore novel therapeutic approaches that may alleviate the suffering of this patient population.

Purpose: The overall trial objectives are to evaluate the efficacy and safety of taurine supplementation in treating and managing prolonged symptoms related to LC, focusing on neurocognitive-associated symptoms and fatigue.

Hypothesis: Increasing taurine levels in the body through treatment with taurine supplements will have a beneficial effect on Long COVID symptoms particularly neurocognitive-associated symptoms and fatigue.

Justification: Previous studies have suggested a correlation between low plasma taurine levels and symptoms associated with Long COVID. Reduced plasma taurine levels have also been observed in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). The decreasing trajectory of taurine levels observed in long COVID could partly explain the fatigue, as taurine plays multiple roles in skeletal muscle function, the central nervous system, and energy metabolism. Furthermore, in various clinical and preclinical studies, including antioxidant, anti-aging, cytoprotective, and cardioprotective effects, taurine has demonstrated various therapeutic activities. Taurine also has a role in neuromodulation and the treatment of other central nervous system disorders, including depression. These findings suggest that taurine may be important in addressing the persistent symptoms and adverse outcomes in LC patients.

Given the robust association between taurine levels and symptoms and adverse outcomes of LC and the safety profile, there is a strong biological and clinical rationale for investigating taurine supplementation. There is a lack of effective treatments for LC, and exploring taurine supplementation as a novel therapeutic approach is justified and holds the potential to significantly improve the lives of affected individuals with an excellent safety profile.

Objectives: The overall trial objectives are to evaluate the efficacy and safety of taurine supplementation in treating and managing prolonged symptoms related to LC, focusing on neurocognitive-associated symptoms and fatigue.

Inclusion Criteria:

1. Age ≥18 years;
2. Positive COVID-19 test by nasopharyngeal swab RT-PCR test, antibody or antigen tests at least 3 months prior to randomization; OR Presumed COVID-19 assessed by the site investigator (no positive COVID-19 test) with acute illness after October 15, 2019, and at least 3 months prior to randomization.
3. If participants have treatable symptoms, they should have had a stable regimen of treatment prior to entering the study (i.e. started treatment for at least 4 weeks).
4. Lingering COVID-19 symptoms beyond 3 months from onset of acute COVID and symptoms have lasted at least 2 months. The onset of COVID is considered the earliest of two dates: the date of positive testing or the date of first symptoms.
5. Lingering symptoms from COVID-19 present at the time of randomization.
6. Individuals of childbearing potential (as assessed by the overseeing Investigator) who are sexually active must agree to practice true abstinence or use at least one highly effective method of contraception while on study treatment. Highly effective methods of contraception must be discussed and approved by the overseeing Investigator (refer to Section 5 Contraception of the Master Protocol, and Section 13.1.2 of this protocol).
7. Must be able to provide informed consent and both willing and able to comply with study requirements.
8. Medications prescribed for treating fatigue or cognition have been discontinued for four weeks prior to enrolment and randomization. These include sildenafil, modafinil (Provigil), or armodafinil (Nuvigil), guanfacine, N-acetyl cysteine, and stimulant medications used for attention-deficit hyperactivity disorder (ADHD).

Exclusion Criteria:

1. Patients who had mechanical ventilation or extracorporeal membrane oxygen (ECMO) for COVID-19.
2. Current end-organ failure, organ transplantation, or current hospitalization in an acute care hospital.
3. Contraindications to the study intervention.
4. Currently already on study intervention(s).
5. Co-enrolment in another interventional trial (co-enrolment in an observational study is permitted).
6. Currently pregnant or breastfeeding.
7. The participant is currently enrolled in another clinical trial to treat neurocognitive symptoms in LC.