inclusion criteria: • male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). for the boostability and protection-against-vocs subset: existing participants enrolled to receive a third dose of bnt162b2 at 30 µg or bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at rerandomization. newly enrolled participants enrolled to receive 2 doses of bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at enrollment. existing participants enrolled to receive a third dose of bnt162b2 at 5 or 10 µg; male or female participants ≥18 years at rerandomization. note that participants \<18 years of age cannot be enrolled in the eu. * participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. * healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. * participants who, in the judgment of the investigator, are at risk for acquiring covid-19. * boostability and protection-against-vocs existing participant subset only: participants who provided a serum sample at visit 3, with visit 3 occurring within the protocol-specified window. * capable of giving personal signed informed consent

inclusion criteria: • male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). for the boostability and protection-against-vocs subset: existing participants enrolled to receive a third dose of bnt162b2 at 30 µg or bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at rerandomization. newly enrolled participants enrolled to receive 2 doses of bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at enrollment. existing participants enrolled to receive a third dose of bnt162b2 at 5 or 10 µg; male or female participants ≥18 years at rerandomization. note that participants \<18 years of age cannot be enrolled in the eu. * participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. * healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. * participants who, in the judgment of the investigator, are at risk for acquiring covid-19. * boostability and protection-against-vocs existing participant subset only: participants who provided a serum sample at visit 3, with visit 3 occurring within the protocol-specified window. * capable of giving personal signed informed consent

inclusion criteria: • male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). for the boostability and protection-against-vocs subset: existing participants enrolled to receive a third dose of bnt162b2 at 30 µg or bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at rerandomization. newly enrolled participants enrolled to receive 2 doses of bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at enrollment. existing participants enrolled to receive a third dose of bnt162b2 at 5 or 10 µg; male or female participants ≥18 years at rerandomization. note that participants <18 years of age cannot be enrolled in the eu. - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - boostability and protection-against-vocs existing participant subset only: participants who provided a serum sample at visit 3, with visit 3 occurring within the protocol-specified window. - capable of giving personal signed informed consent

inclusion criteria: • male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). for the boostability and protection-against-vocs subset: existing participants enrolled to receive a third dose of bnt162b2 at 30 µg or bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at rerandomization. newly enrolled participants enrolled to receive 2 doses of bnt162b2sa; male or female participants between the ages of 18 and 55 years, inclusive, at enrollment. existing participants enrolled to receive a third dose of bnt162b2 at 5 or 10 µg; male or female participants ≥18 years at rerandomization. note that participants <18 years of age cannot be enrolled in the eu. - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - boostability and protection-against-vocs existing participant subset only: participants who provided a serum sample at visit 3, with visit 3 occurring within the protocol-specified window. - capable of giving personal signed informed consent

inclusion criteria: - male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). for the boostability and protection-against-vocs subset (both existing and newly enrolled), male or female participants between the ages of 18 and 55 years, inclusive, at rerandomization/enrollment. note that participants <18 years of age cannot be enrolled in the eu. - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - boostability and protection-against-vocs existing participant subset only: participants who provided a serum sample at visit 3, with visit 3 occurring within the protocol-specified window. - capable of giving personal signed informed consent

inclusion criteria: - male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). for the boostability and protection-against-vocs subset (both existing and newly enrolled), male or female participants between the ages of 18 and 55 years, inclusive, at rerandomization/enrollment. note that participants <18 years of age cannot be enrolled in the eu. - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - boostability and protection-against-vocs existing participant subset only: participants who provided a serum sample at visit 3, with visit 3 occurring within the protocol-specified window. - capable of giving personal signed informed consent

inclusion criteria: - male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). note that participants <18 years of age cannot be enrolled in the eu. - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - capable of giving personal signed informed consent

inclusion criteria: - male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥12 years, inclusive, at randomization (dependent upon study phase). note that participants <18 years of age cannot be enrolled in the eu. - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - capable of giving personal signed informed consent

inclusion criteria: - male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥16 years, inclusive, at randomization (dependent upon study phase). - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - capable of giving personal signed informed consent

inclusion criteria: - male or female participants between the ages of 18 and 55 years, inclusive, 65 and 85 years, inclusive, or ≥16 years, inclusive, at randomization (dependent upon study phase). - participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. - healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. - participants who, in the judgment of the investigator, are at risk for acquiring covid-19. - capable of giving personal signed informed consent