Inclusion Criteria:  Willing and able to provide written informed consent prior to performing study procedures. Males and non-pregnant females who are between 18 to 59 years of age. Asymptomatic, RT-PCR negative (at screening) AND without a known prior history of COVID-19 infection. Provides documentation showing completion of a FDA authorized or approved COVID-19 vaccination regimen, where the last administration was ≥ 6 months (180 days) from the study enrollment date.  IF FEMALE PARTICIPANT: A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least 1 of the following conditions applies:  Is not a woman of child-bearing potential (WOCBP); OR Is a WOCBP and using an acceptable contraceptive method during the intervention period (for a minimum of 90 days after NDV-HXP-S vaccination). The investigator should evaluate the effectiveness of the contraceptive method in relationship to the first dose of study intervention. Only highly effective methods of contraception that have a low user dependency or a combination of highly effective methods that are user dependent may be used.  IF MALE PARTICIPANT: Agrees to the following requirements during the intervention period and for at least 90 days after NDV-HXP-S vaccination, which corresponds to the time needed to eliminate reproductive safety risk of the study intervention(s):  Refrain from donating sperm AND be abstinent from heterosexual intercourse with a female of childbearing potential as their preferred and usual lifestyle (abstinent on a long-term and persistent basis) and agree to remain abstinent; OR Must agree to use a male condom when engaging in any activity that allows for passage of ejaculate to another person. In addition to male condom use, a highly effective method of contraception may be considered in WOCBP partners of male participants. Participant understands and agrees to comply with planned study procedures. Participant agrees to not participate in another clinical trial for treatment of COVID-19 or SARS-CoV-2 through Day 365.  Participant agrees to not receive any other vaccination (including COVID-19 vaccine) through Day 56.  Provides consent for release of information for hospitalization records and other medically attended visits during the study.  Exclusion Criteria:  Clinical and/or laboratory evidence indicative of COVID-19 infection. Demonstrates a STRONG COVID-19 positive antibody serology (≥ 40 AU/ml) or a NEGATIVE COVID-19 serology on screening. History of hypersensitivity to egg products. History of severe reactions to vaccinations. Potential for prior NDV exposures (i.e., experience as a bird-handler, poultry farmer, or scientist conducting research with NDV). History of an immunocompromising medical condition (such as primary immunodeficiencies, AIDS, or neutropenia). Current or recent use of immunosuppressive medications (i.e. any systemic corticosteroids, chemotherapeutics, immunoglobulin therapies, etc.) based on the assessment of their half-life by the investigator. Any history of HIV, hepatitis C, hepatitis B (by laboratory testing and/or history), Guillain-Barré syndrome, and/or recent receipt of immunoglobulins and/or blood products. Pregnancy or actively breastfeeding. Other medical condition which may place subject at increased risk for harm due to participation in the study as determined by the investigator. In the opinion of the investigator that it would be unwise to allow the participant to be randomized into the study, including those persons who the investigator would consider as high risk of SARS-CoV-2 exposure, including healthcare workers with direct patient care and laboratory workers who handle SARS-CoV-2. Participants at higher risk of severe COVID-19, as defined by CDC guidance (https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/index.html). This guidance includes details regarding older adults, people with specific medical conditions, and pregnant and recently pregnant people. Participants with fever or signs of acute infection, including symptoms that could indicate SARS-CoV-2 infection. Participants with a history of chronic rhinitis, nasal septal defect, cleft palate, nasal polyps, or other nasal abnormality that might affect vaccine administration. Participants who prepare food in the food industry and childcare workers who have direct contact with children 5 years of age or younger.  Participants who have close or household high-risk contacts including but not limited to:  Persons more than or equal to 65 years of age Children less than or equal to 5 years of age. Residents of nursing homes. Persons of any age with significant chronic medical conditions as well as immunosuppression or cancer. Women who are pregnant, trying to become pregnant, or breastfeeding. Participants who are students, post-doctoral candidates, or trainees of the study site, or are members of the research staff.