A minimum of 10 days must pass between the first M7824 administration and the second. Any dose that cannot be accommodated within this window will be skipped and the dose not made up. 3.2.2 M7824 Subjects in Arms A, B and C will be scheduled to receive M7824 at a flat dose of 1,200 mg IV on days 1 and 15. Subjects will receive M7824 via IV infusion over 1 hour (-10 minutes / +20 minutes, that is, over 50 to 80 minutes) once every 2 weeks. M7824 will be administered as a "flat" dose of 1,200 mg independent of body weight. M7824 is administered as an intravenous infusion with a mandatory 0.2 micron in-line filter. In order to mitigate potential infusion-related reactions, premedication with an antihistamine and with acetaminophen (for example, 25-50 mg diphenhydramine and 500-650 mg acetaminophen) may be given within approximately 30 to 60 minutes prior to dosing of M7824. Steroids as premedication are not permitted. If hypersensitivity reaction occurs, the subject should be treated according to the best available medical practice.  Risk for cutaneous keratocanthoma/squamous cell carcinoma with administration of M7824 All cases of skin lesions suspicious for the above will be preferably referred to Dermatology at the NIH. In cases where patients are unable to follow up with Dermatology at the NIH, keratoacanthomas may be managed by an outside dermatologist. Patients will then undergo routine follow-up skin exams and treatment as deemed appropriate by the Dermatologist. 3.2.3 Adenoviral vaccines ETBX 011, 051 and 061 will be given as subcutaneous injections, on day 1 of treatment to subjects in Arms B and C. ETBX-011, ETBX-051 and ETBX-061 will be administered by subcutaneous injection in the upper arm or anterolateral upper thigh after preparation of the site with alcohol. A 1 to 1⁄2 inch, 20- to 25- gauge needle should be used for each individual administration. It is preferred to administer ETBX-011, ETBX-051 and ETBX-061 in separate limbs. The limb of administration should be documented in the medical record. When administered in the same thigh, injection sites should be separated by at least 5 cm. 3.2.4 N-803 N-803 will be given via subcutaneous injection to subjects in Arm C at a dose of 15 mcg/kg on day 1. N-803 dosing will be calculated using a weight obtained within 5 days prior to the first dose. 30 Abbreviated Title: Neoadjuvant IO for HNSCC Version Date: August 31, 2022 Injection should occur in the abdomen. Depending on the injection volume required, the dose of N-803 may be administered as a single injection or multiple injections at the discretion of the investigator.