inclusion criteria: main part: 1. healthy japanese male and female adult participants aged \>= 20 years of age at the time of signing of informed consent. 2. participant who completed 2 doses primary vaccinations with another specified mrna vaccine which is available in japan 6 to 12 months prior to the trial vaccination. extension part: 3. participants who received the first trial vaccination at least 5 months earlier and are currently enrolled in the main part (ie, not have withdrawn or discontinued early).

inclusion criteria: main part: 1. healthy japanese male and female adult participants aged \>= 20 years of age at the time of signing of informed consent. 2. participant who completed 2 doses primary vaccinations with another specified mrna vaccine which is available in japan 6 to 12 months prior to the trial vaccination. extension part: 3. participants who received the first trial vaccination at least 5 months earlier and are currently enrolled in the main part (ie, not have withdrawn or discontinued early).

inclusion criteria: main part: healthy japanese male and female adult participants aged >= 20 years of age at the time of signing of informed consent. participant who completed 2 doses primary vaccinations with another specified mrna vaccine which is available in japan 6 to 12 months prior to the trial vaccination. extension part: participants who received the first trial vaccination at least 5 months earlier and are currently enrolled in the main part (ie, not have withdrawn or discontinued early).

inclusion criteria: main part: healthy japanese male and female adult participants aged >= 20 years of age at the time of signing of informed consent. participant who completed 2 doses primary vaccinations with another specified mrna vaccine which is available in japan 6 to 12 months prior to the trial vaccination. extension part: participants who received the first trial vaccination at least 5 months earlier and are currently enrolled in the main part (ie, not have withdrawn or discontinued early).

inclusion criteria: healthy japanese male and female adult subjects aged >= 20 years of age at the time of signing of informed consent. participant who completed 2 doses primary vaccinations with another specified mrna vaccine which is available in japan 6 to 12 months prior to the trial vaccination.

inclusion criteria: healthy japanese male and female adult subjects aged >= 20 years of age at the time of signing of informed consent. participant who completed 2 doses primary vaccinations with another specified mrna vaccine which is available in japan 6 to 12 months prior to the trial vaccination.