inclusion criteria: * aged between 18 and 60 years. * able to understand the content of informed consent and willing to sign the informed consent * able and willing to complete all the secluded study process during the whole 6 months study follow-up period. * negative in hiv diagnostic test. * negative in serum antibodies (igg and igm) screening of covid-19. * axillary temperature ≤37.0°c. * the bmi index is 18.5-30.0. * general good health as established by medical history and physical examination.

inclusion criteria: * aged between 18 and 60 years. * able to understand the content of informed consent and willing to sign the informed consent * able and willing to complete all the secluded study process during the whole 6 months study follow-up period. * negative in hiv diagnostic test. * negative in serum antibodies (igg and igm) screening of covid-19. * axillary temperature ≤37.0°c. * the bmi index is 18.5-30.0. * general good health as established by medical history and physical examination.

inclusion criteria: - aged between 18 and 60 years. - able to understand the content of informed consent and willing to sign the informed consent - able and willing to complete all the secluded study process during the whole 6 months study follow-up period. - negative in hiv diagnostic test. - negative in serum antibodies (igg and igm) screening of covid-19. - axillary temperature ≤37.0°c. - the bmi index is 18.5-30.0. - general good health as established by medical history and physical examination.

inclusion criteria: - aged between 18 and 60 years. - able to understand the content of informed consent and willing to sign the informed consent - able and willing to complete all the secluded study process during the whole 6 months study follow-up period. - negative in hiv diagnostic test. - negative in serum antibodies (igg and igm) screening of covid-19. - axillary temperature ≤37.0°c. - the bmi index is 18.5-30.0. - general good health as established by medical history and physical examination.