PTX-COVID19-B, an mRNA Humoral Vaccine, Intended for Prevention of COVID-19 in a General Population. This Study is Designed to Demonstrate the Safety, Tolerability, and Immunogenicity of PTX-COVID19-B in Comparison to the Pfizer-BioNTech COVID-19 Vaccine.

Exclusion Criteria

• •1. History of an acute or chronic medical condition that, in the opinion of the investigator, would render vaccination unsafe or would interfere with the evaluation of responses.
• •2. History of ongoing clinical condition or medication or treatments that may adversely affect the immune system.
• •3. Subjects with pulse oximetry \<90% at screening and prior to each vaccination.
• •4. Individuals who are antigen positive, seropositive or reverse transcriptase polymerase chain reaction (RT-PCR) positive for SARS-CoV-2, including prior to a second dose of PTX-COVID19-B.
• •5. Individuals who are at increased risk of exposure to SARS-CoV-2 (e.g., healthcare workers, emergency responders).
• •6. Close contact of anyone known to have SARS-CoV-2 infection within 30 days prior to vaccine administration.
• •7. Individuals with any elevated (Grade 1 or higher) laboratory test assessed as clinically significant for age/sex by the investigator at screening.
• •8. Individuals known to have anti-platelet antibodies.
• •9. Individuals with myocarditis and/or arrythmias.
• •10. Active neoplastic disease (excluding non-melanoma skin cancer that was successfully treated) or a history of any hematological malignancy. ("Active" is defined as having received treatment within the past five years).
• •11. Long-term (\> two (2) weeks) use of oral or parenteral steroids or high-dose inhaled steroids (\> 800 μg/day of beclomethasone dipropionate or equivalent) within six months before screening (nasal and topical steroids are allowed).
• •12. History of autoimmune, inflammatory disease, or potential immune-mediated medical conditions (PIMMCs).
• •13. Women currently pregnant, lactating, or planning a pregnancy between enrollment and Day 42.
• •14. History of immune thrombocytopenic purpura (ITP).
• •15. History of Guillain-Barré Syndrome or any degenerative neurology disorder.
• •16. History of anaphylactic-type reaction to any injected vaccines.
• •17. Known or suspected hypersensitivity to one or more of the components of the vaccine.
• •18. Known history of alcohol abuse, illicit drug use, physical dependence to any opioid, or any history of drug abuse or addiction within 12 months of screening.
• •19. Acute illness or fever (temperature \>37.5C) within three (3) days before study enrollment (enrollment may be delayed for full recovery if acceptable to the investigator and within Protocol-defined windows).
• •20. Individuals currently participating or planning to participate in a study that involves an experimental agent (vaccine, drug, biologic, device, or medication); or who have received an experimental agent within one (1) month (three (3) months for immunoglobulins) before enrollment in this study; or who expect to receive another experimental agent up to Day 90 in this study.
• •21. Receipt of immunoglobulin or another blood product within the three (3) months before enrollment in this study or those who expect to receive immunoglobulin or another blood product during this study.
• •22. Individuals using prescription medications for prophylaxis of SARS-CoV-2.
• •23. Individuals who plan to receive another vaccine within the first three (3) months of the study (except influenza vaccine which should not be given within two (2) weeks of vaccine).
• •24. Receipt of any other SARS-CoV-2 or other experimental coronavirus (MERS, SARS etc.) vaccine at any time prior to or during the study.
• •25. Receipt of any investigational vaccine or investigational drug within one (1) month of enrollment and through the end of the study (one (1) year after the last vaccination).
• •26. Planning international travel from enrollment through Day 43.
• •27. History of surgery or major trauma within 12 weeks of screening, or surgery planned during the study.
• •28. Significant blood loss (\> 400 mL) or has donated one or more units of blood (within 56 days for males and 84 days for females) or plasma (within two (2) weeks) prior to study participation.
• •29. Positive urine drugs of abuse screen test result.
• •30. Positive screen for HIV-1 and HIV-2 antibodies, HBsAg, or HCV antibody.
• •31. Involved in the planning or conduct of this study.
• •32. Unwilling or unlikely to comply with the requirements of the study.
• •Exclusion from the open label safety extension:
• •33. Participation in a study that would affect potential immunogenicity evaluation during ongoing participation in this study. Participation in any other study is allowed after Day 90.