inclusion criteria: subject's meeting all the following criteria are eligible to participate in this study: * males or females 18 to 45 (inclusive) years of age, at screening. * healthy participants as determined based on medical history, clinical laboratory results, vital sign measurements, and physical examination at screening. * subjects not previously vaccinated with any covid-19 vaccine or subjects who have completed the vaccination according to an officially accepted scheme (e.g., healthcare workers), at least 4 weeks prior to enrollment, with an authorized vaccine which induces neutralizing antibodies against the sars-cov-2 spike protein. * willing and able to give informed consent. * willing to accept following contraceptive measures:

inclusion criteria: subject's meeting all the following criteria are eligible to participate in this study: * males or females 18 to 45 (inclusive) years of age, at screening. * healthy participants as determined based on medical history, clinical laboratory results, vital sign measurements, and physical examination at screening. * subjects not previously vaccinated with any covid-19 vaccine or subjects who have completed the vaccination according to an officially accepted scheme (e.g., healthcare workers), at least 4 weeks prior to enrollment, with an authorized vaccine which induces neutralizing antibodies against the sars-cov-2 spike protein. * willing and able to give informed consent. * willing to accept following contraceptive measures:

inclusion criteria: subject's meeting all the following criteria are eligible to participate in this study: - males or females 18 to 45 (inclusive) years of age, at screening. - healthy participants as determined based on medical history, clinical laboratory results, vital sign measurements, and physical examination at screening. - subjects not previously vaccinated with any covid-19 vaccine or subjects who have completed the vaccination according to an officially accepted scheme (e.g., healthcare workers), at least 4 weeks prior to enrollment, with an authorized vaccine which induces neutralizing antibodies against the sars-cov-2 spike protein. - willing and able to give informed consent. - willing to accept following contraceptive measures:

inclusion criteria: subject's meeting all the following criteria are eligible to participate in this study: - males or females 18 to 45 (inclusive) years of age, at screening. - healthy participants as determined based on medical history, clinical laboratory results, vital sign measurements, and physical examination at screening. - subjects not previously vaccinated with any covid-19 vaccine or subjects who have completed the vaccination according to an officially accepted scheme (e.g., healthcare workers), at least 4 weeks prior to enrollment, with an authorized vaccine which induces neutralizing antibodies against the sars-cov-2 spike protein. - willing and able to give informed consent. - willing to accept following contraceptive measures: