Study to Reinforce Immunity (STRI) Phase 2 Clinical Trial

Inclusion Criteria: 1. Adults residing in the United States aged 18 years or older. 2. Provision of documentation of positive SARS-CoV-2 testing (via RT-PCR, rapid antigen testing) performed less than 7 days before screening, either via direct upload or confirmation from PCP. 1. electronic secure document upload; 2. allowing STRI Personnel to contact the PCP to confirm diagnosis; or 3. allowing STRI Personnel to contact the laboratory where the RT-PCR analysis was performed 3. Initial date of onset of COVID-19 signs/symptoms 7 days or less from date of STRI Screening and Randomization (i.e., Day 0). 4. During screening (Day 0): 1. participant-reported response of "Mild" or "Moderate" in response to the question "Overall, how severe were your infection symptoms today?" (FLU-PRO Plus Global Additional Daily Diary Items Question 1) 2. During prescreening, participant self-reported response of "A little worse" or "Somewhat worse" or "Much worse" or "About the same" in response to the question "Overall, how were your infection symptoms today compared to yesterday?" (FLU-PRO Plus Global Additional Daily Diary Items Question 2) 3. During prescreening, participant-reported response of "No" in response to the question "Have you returned to your usual health today?" (FLU-PRO Plus Global Additional Daily Diary Items Question 6) 4. At least TWO participant self-reported responses of "Somewhat," "Quite A Bit," or "Very Much" in any FLU-PRO Plus domain other than smell and taste (i.e., nose, throat, eyes, chest/respiratory, head, gastrointestinal, or body/systemic domains) 5. Ability to self-measure and self-report body temperature, and peripheral oxygen saturation (with STRI provided thermometer and STRI provided pulse oximeter). 6. Provision of signed and dated electronic informed consent form (via 21 CFR Part 11 compliant platform). 7. Provision of participant's primary care physician (PCP) name and phone number. 8. Consent to allow STRI Personnel to contact PCP for any reason and discuss participant's medical history and/or obtain participant's medical records. 9. Stated willingness to comply with all study procedures and availability for the duration of the study, including intent to comply with lifestyle considerations throughout Study duration. 10. Ability to take oral medication and be willing to adhere to the STRI Intervention Product (STRI Formula or placebo as capsules) regimen. 11. Ability to use the internet daily and check email daily. 12. Ability and consent to send and receive SMS text messages via cellular phone. 13. Provision of information (name, email address, and cellular phone number) of an emergency contact (e.g., family member/friend/colleague) willing to communicate with STRI Personnel in case the participant deteriorates. 14. Willingness to discontinue any dietary supplement that contains any active ingredient in STRI Formula (ascorbic acid, cholecalciferol, zinc, copper, quercetin, hesperidin, caffeic acid, epigallocatechin gallate, bovine lactoferrin) for the duration of the Study. 15. For men and women with child-bearing potential (as defined below), willingness to use adequate contraception for at least 100 days after beginning the Study. Exclusion Criteria: 1. Inability to comply with study or follow-up procedures, or provide regular updates to their health status when contacted by the STRI Personnel via email, SMS, or phone. 2. Any prior or current hospitalization for COVID-19 or any need for hospitalization for any reason. 3. Any prior or current treatment with any agent for COVID-19. 4. Any known allergies or known toxicities to any of the specific ingredients in STRI Formula (including ascorbic acid, vitamin D, zinc, copper, amla, caffeic acid, coffee, bovine lactoferrin, milk, quercetin, hesperidin, oranges, citrus fruits, and/or green tea) 5. Body Mass Index \> 40 based on participant-reported weight and participant-reported height. 6. Participant-reported weight of less than 35kg. 7. Any history of radiation or chemotherapy for cancer within the last 3 months. 8. Any history of cardiac arrythmias, hemochromatosis, renal (including any known GFR \< 60mL/min) or hepatic disease (including chronic liver disease). 9. Any history of chronic pulmonary disorders 10. Any history of any gastrointestinal surgery or disease (including bariatric surgery or gastrointestinal resection, inflammatory bowel disease, or chronic intestinal diseases, such as (but not limited to) eosinophilic enteritis or autoimmune enteritis). 11. Any history of mineral or vitamin overload or deficiency (including chronic iron overload states, copper overload states, or ascorbic acid, vitamin D, zinc, or copper deficiencies). 12. Any history of any adverse event to green tea extract or any herbal products. 13. Prescreening Alcohol Use Disorders Identification Test (AUDIT) score of 8 or more indicating hazardous or harmful alcohol consumption, or alcohol dependence. 14. Pregnant or nursing/breastfeeding participants or participants intending to become pregnant within the next 24 months. 15. Men or premenopausal women not using adequate contraception. 16. Any other factors as judged by the principal investigator that would cause harm or increased risk to the participant or preclude the participant's full adherence with or completion of the study.