Bivalent vaccine no longer epidemiologically relevant.

The purpose of this clinical trial is to learn about the safety and immune responses of the study vaccine (called a bivalent BNT162b2 Omicron containing vaccine) in healthy infants and children. Sub study A of this clinical trial will test up to four different dose levels of the vaccine in infants who are under 6 months of age and have not previously received a coronavirus vaccination.

This will be a 3- dose primary series of the study vaccine with each dose separated by 8 weeks.

Inclusion Criteria:

1. Healthy male or female participants 72 through 102 days of age, at the time of randomization (the day of birth is considered Day 1 of life).
2. Male or female participants born at greater than 32 weeks of gestation.

Exclusion Criteria:

1. Receipt of any nonstudy vaccine within 14 days, before study intervention administration (Dose 1 only).
2. Receipt of medications intended to prevent COVID-19.
3. Previous or current diagnosis of MIS-C (Multisystem Inflammatory Syndrome In Children).
4. History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (e.g., anaphylaxis) to any component of the study intervention(s).
5. Immunocompromised individuals with known or suspected immunodeficiency, as determined by history and/or laboratory/physical examination.
6. Individuals with a history of autoimmune disease or an active autoimmune disease requiring therapeutic intervention.
7. Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection.
8. Other medical (e.g,. major known congenital malformation or serious chronic disorder such as seizures) or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. Note: This includes both conditions that may increase the risk associated with study intervention administration or conditions that may interfere with the interpretation of study results.
9. Previous vaccination with any non-study coronavirus vaccine.
10. Individuals who receive treatment with immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids.
11. Receipt of blood/plasma products, immunoglobulin, or monoclonal antibodies (except palivizumab and hepatitis B immunoglobulin), from 60 days before study intervention administration, or receipt of any passive antibody therapy specific to COVID-19 from 90 days before study intervention administration, or planned receipt throughout the study.
12. Receipt of other study intervention within 28 days prior to study entry through and including 28 days after the last dose of study intervention, with the exception of non-Pfizer interventional studies for prevention of COVID-19, which are prohibited throughout study participation.
13. Investigator site staff directly involved in the conduct of the study and their family members, site staff otherwise supervised by the investigator, and sponsor and sponsor delegate employees directly involved in the conduct of the study and their family members. Children or grandchildren who are direct descendants of investigator site staff or sponsor and sponsor delegate employees directly involved in the conduct of the study.