A Study to Evaluate Safety, Tolerability, & Immunogenicity of Multiple Formulations of BNT162b2 Against COVID-19 in Healthy Adults

This study will compare the safety and tolerability of lyophilized BNT162b2 presented in single dose vials to those of frozen-liquid BNT162b2 in multidose vials and determine whether the immune response is noninferior. Separately, the study will also describe the safety and immunogenicity of frozen-liquid BNT162b2 with lipid nanoparticle size at the upper end of specification and ready to use BNT162b2 (the immediate manufacturing precursor to the lyophilate). Additionally, the study will describe the safety and immunogenicity of an additional dose of frozen liquid BNT162b2 to participants who already received the 2-dose schedule of lyophilized BNT162b2.

* 2-dose schedule (separated by 21 days)
* At a dose of 30µg (as studied in the Phase 2/3 study C4591001)
* In healthy adults 18 through 55 years of age
* The duration of the study for each participant will be approximately 2 months (3 visits in total)
* The study will be conducted in the United States


Eligibility Criteria:
Inclusion Criteria:

* Male or female participants 18 - 55 years of age, inclusive, at Visit 1, (Day 1).
* Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures.
* Healthy participants who are determined by medical history, physical examination (if required), and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with pre-existing stable disease, defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 6 weeks before enrolment, can be included.
* Capable of giving personal signed informed consent, which includes compliance with the requirements and restrictions listed in the ICD and in the protocol.
* For Dose 3: Participants who received BOTH doses of the lyophilized formulation of BNT162b2 as part of the initial study.

Exclusion Criteria:

* Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
* Known infection with HIV, HCV, or HBV.
* History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention(s).
* Previous clinical (based on COVID-19 symptoms/signs alone, if a SARS-CoV-2 NAAT result was not available) or microbiological (based on COVID-19 symptoms/signs and a positive SARS-CoV-2 NAAT result) diagnosis of COVID-19.
* Immunocompromised individuals with known or suspected immunodeficiency, as determined by history and/or laboratory/physical examination.
* Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection.
* Women who are pregnant or breastfeeding.
* Previous vaccination with any coronavirus vaccine.
* Receipt of medications intended to prevent COVID-19.
* Individuals who receive treatment with radiotherapy or immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids (if systemic corticosteroids are administered for ≥14 days at a dose of ≥20 mg/day of prednisone or equivalent), eg, for cancer or an autoimmune disease, or planned receipt throughout the study. Inhaled/nebulized, intra-articular, intrabursal, or topical (skin or eyes) corticosteroids are permitted.
* Receipt of blood/plasma products or immunoglobulin, from 60 days before study intervention administration or planned receipt throughout the study.
* Participation in other studies involving study intervention within 28 days prior to study entry and/or during study participation / Previous participation in other studies involving study intervention containing lipid nanoparticles (LNPs).
* Previous participation in other studies involving study intervention containing lipid nanoparticles.
* Investigator site staff or Pfizer/BioNTech employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family members.