part a: inclusion criteria: * male or female, by birth, ≥ 18 years old at screening. * willing and able to comply with scheduled visits, laboratory tests, complete diaries, and other study procedures. * body mass index (bmi) between 18 to 40 kg/m2. * has received a complete covid-19 vaccination programme (two administrations, prime and boosting) at least 182 days and with a maximum of 365 days before screening with comirnaty vaccine. * has a negative covid-19 polymerase chain reaction (pcr) test at screening. * willing to avoid all other vaccines within 4 weeks before and after vaccination in this study (day 0). seasonal influenza vaccination is allowed if it is received at least 14 days before or after vaccination. * willing to refrain from blood donation during the study. * women of childbearing potential must have a negative urine pregnancy test at screening and prior to vaccination. * women of childbearing potential must be willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the vaccination. * males who are not sterilised, must be willing to avoid impregnating female partners from screening until 8 weeks after vaccination. * willing and able to provide written informed consent prior the initiation of any study procedures. part a:

part a: inclusion criteria: * male or female, by birth, ≥ 18 years old at screening. * willing and able to comply with scheduled visits, laboratory tests, complete diaries, and other study procedures. * body mass index (bmi) between 18 to 40 kg/m2. * has received a complete covid-19 vaccination programme (two administrations, prime and boosting) at least 182 days and with a maximum of 365 days before screening with comirnaty vaccine. * has a negative covid-19 polymerase chain reaction (pcr) test at screening. * willing to avoid all other vaccines within 4 weeks before and after vaccination in this study (day 0). seasonal influenza vaccination is allowed if it is received at least 14 days before or after vaccination. * willing to refrain from blood donation during the study. * women of childbearing potential must have a negative urine pregnancy test at screening and prior to vaccination. * women of childbearing potential must be willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the vaccination. * males who are not sterilised, must be willing to avoid impregnating female partners from screening until 8 weeks after vaccination. * willing and able to provide written informed consent prior the initiation of any study procedures. part a:

part a: inclusion criteria: male or female, by birth, ≥ 18 years old at screening. willing and able to comply with scheduled visits, laboratory tests, complete diaries, and other study procedures. body mass index (bmi) between 18 to 40 kg/m2. has received a complete covid-19 vaccination programme (two administrations, prime and boosting) at least 182 days and with a maximum of 365 days before screening with comirnaty vaccine. has a negative covid-19 polymerase chain reaction (pcr) test at screening. willing to avoid all other vaccines within 4 weeks before and after vaccination in this study (day 0). seasonal influenza vaccination is allowed if it is received at least 14 days before or after vaccination. willing to refrain from blood donation during the study. women of childbearing potential must have a negative urine pregnancy test at screening and prior to vaccination. women of childbearing potential must be willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the vaccination. males who are not sterilised, must be willing to avoid impregnating female partners from screening until 8 weeks after vaccination. willing and able to provide written informed consent prior the initiation of any study procedures. part a:

part a: inclusion criteria: male or female, by birth, ≥ 18 years old at screening. willing and able to comply with scheduled visits, laboratory tests, complete diaries, and other study procedures. body mass index (bmi) between 18 to 40 kg/m2. has received a complete covid-19 vaccination programme (two administrations, prime and boosting) at least 182 days and with a maximum of 365 days before screening with comirnaty vaccine. has a negative covid-19 polymerase chain reaction (pcr) test at screening. willing to avoid all other vaccines within 4 weeks before and after vaccination in this study (day 0). seasonal influenza vaccination is allowed if it is received at least 14 days before or after vaccination. willing to refrain from blood donation during the study. women of childbearing potential must have a negative urine pregnancy test at screening and prior to vaccination. women of childbearing potential must be willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the vaccination. males who are not sterilised, must be willing to avoid impregnating female partners from screening until 8 weeks after vaccination. willing and able to provide written informed consent prior the initiation of any study procedures. part a:

inclusion criteria: male or female, by birth, ≥ 18 years old at screening. willing and able to comply with scheduled visits, laboratory tests, complete diaries, and other study procedures. body mass index (bmi) between 18 to 40 kg/m2. has received a complete covid-19 vaccination programme (two administrations, prime and boosting) at least 182 days and with a maximum of 365 days before screening with comirnaty vaccine. has a negative covid-19 polymerase chain reaction (pcr) test at screening. willing to avoid all other vaccines within 4 weeks before and after vaccination in this study (day 0). seasonal influenza vaccination is allowed if it is received at least 14 days before or after vaccination. willing to refrain from blood donation during the study. women of childbearing potential must have a negative urine pregnancy test at screening and prior to vaccination. women of childbearing potential must be willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the vaccination. males who are not sterilised, must be willing to avoid impregnating female partners from screening until 8 weeks after vaccination. willing and able to provide written informed consent prior the initiation of any study procedures.

inclusion criteria: male or female, by birth, ≥ 18 years old at screening. willing and able to comply with scheduled visits, laboratory tests, complete diaries, and other study procedures. body mass index (bmi) between 18 to 40 kg/m2. has received a complete covid-19 vaccination programme (two administrations, prime and boosting) at least 182 days and with a maximum of 365 days before screening with comirnaty vaccine. has a negative covid-19 polymerase chain reaction (pcr) test at screening. willing to avoid all other vaccines within 4 weeks before and after vaccination in this study (day 0). seasonal influenza vaccination is allowed if it is received at least 14 days before or after vaccination. willing to refrain from blood donation during the study. women of childbearing potential must have a negative urine pregnancy test at screening and prior to vaccination. women of childbearing potential must be willing to use highly effective contraceptive methods or have practiced sexual abstinence from the screening visit until 8 weeks after the vaccination. males who are not sterilised, must be willing to avoid impregnating female partners from screening until 8 weeks after vaccination. willing and able to provide written informed consent prior the initiation of any study procedures.