inclusion criteria: * male or female participants 18 years of age or older. * health care workers (hcws), employees or students in clinical training. * provide written informed consent prior to initiation of any trial procedures. * expected compliance with protocol procedures and availability for clinical follow-up through the last planned visit. * females of non-childbearing potential defined as follows: surgically sterile (history of bilateral tubal ligation/occlusion, bilateral oophorectomy or hysterectomy) or postmenopausal (defined as amenorrhea for ≥12 consecutive months prior to screening \[day 1\] without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. * females of childbearing potential: negative urine pregnancy test (human chorionic gonadotropin within 24 hours prior to each trial vaccination on day 1 and day 29. * females of childbearing potential must use highly effective methods of birth control from 2 weeks before the first administration of the trial vaccine until 3 months following the last administration. the following methods of birth control are considered highly effective when used consistently and correctly: * combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal or transdermal); * progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable or implantable); * intrauterine devices (iuds); * intrauterine hormone-releasing systems (iuss); * bilateral tubal ligation; * vasectomized partner; * sexual abstinence (periodic abstinence \[e.g., calendar, ovulation, symptothermal and post-ovulation methods\] and withdrawal are not acceptable).

inclusion criteria: * male or female participants 18 years of age or older. * health care workers (hcws), employees or students in clinical training. * provide written informed consent prior to initiation of any trial procedures. * expected compliance with protocol procedures and availability for clinical follow-up through the last planned visit. * females of non-childbearing potential defined as follows: surgically sterile (history of bilateral tubal ligation/occlusion, bilateral oophorectomy or hysterectomy) or postmenopausal (defined as amenorrhea for ≥12 consecutive months prior to screening \[day 1\] without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. * females of childbearing potential: negative urine pregnancy test (human chorionic gonadotropin within 24 hours prior to each trial vaccination on day 1 and day 29. * females of childbearing potential must use highly effective methods of birth control from 2 weeks before the first administration of the trial vaccine until 3 months following the last administration. the following methods of birth control are considered highly effective when used consistently and correctly: * combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal or transdermal); * progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable or implantable); * intrauterine devices (iuds); * intrauterine hormone-releasing systems (iuss); * bilateral tubal ligation; * vasectomized partner; * sexual abstinence (periodic abstinence \[e.g., calendar, ovulation, symptothermal and post-ovulation methods\] and withdrawal are not acceptable).

inclusion criteria: - male or female participants 18 years of age or older. - health care workers (hcws), employees or students in clinical training. - provide written informed consent prior to initiation of any trial procedures. - expected compliance with protocol procedures and availability for clinical follow-up through the last planned visit. - females of non-childbearing potential defined as follows: surgically sterile (history of bilateral tubal ligation/occlusion, bilateral oophorectomy or hysterectomy) or postmenopausal (defined as amenorrhea for ≥12 consecutive months prior to screening [day 1] without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. - females of childbearing potential: negative urine pregnancy test (human chorionic gonadotropin within 24 hours prior to each trial vaccination on day 1 and day 29. - females of childbearing potential must use highly effective methods of birth control from 2 weeks before the first administration of the trial vaccine until 3 months following the last administration. the following methods of birth control are considered highly effective when used consistently and correctly: - combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal or transdermal); - progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable or implantable); - intrauterine devices (iuds); - intrauterine hormone-releasing systems (iuss); - bilateral tubal ligation; - vasectomized partner; - sexual abstinence (periodic abstinence [e.g., calendar, ovulation, symptothermal and post-ovulation methods] and withdrawal are not acceptable).

inclusion criteria: - male or female participants 18 years of age or older. - health care workers (hcws), employees or students in clinical training. - provide written informed consent prior to initiation of any trial procedures. - expected compliance with protocol procedures and availability for clinical follow-up through the last planned visit. - females of non-childbearing potential defined as follows: surgically sterile (history of bilateral tubal ligation/occlusion, bilateral oophorectomy or hysterectomy) or postmenopausal (defined as amenorrhea for ≥12 consecutive months prior to screening [day 1] without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. - females of childbearing potential: negative urine pregnancy test (human chorionic gonadotropin within 24 hours prior to each trial vaccination on day 1 and day 29. - females of childbearing potential must use highly effective methods of birth control from 2 weeks before the first administration of the trial vaccine until 3 months following the last administration. the following methods of birth control are considered highly effective when used consistently and correctly: - combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal or transdermal); - progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable or implantable); - intrauterine devices (iuds); - intrauterine hormone-releasing systems (iuss); - bilateral tubal ligation; - vasectomized partner; - sexual abstinence (periodic abstinence [e.g., calendar, ovulation, symptothermal and post-ovulation methods] and withdrawal are not acceptable).

inclusion criteria: - male or female participants 18 years of age or older. - health care workers (hcws), employees or students in the clinical years. - provide written informed consent prior to initiation of any trial procedures. - expected compliance with protocol procedures and availability for clinical follow-up through the last planned visit. - females of non-childbearing potential defined as follows: surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy or hysterectomy) or postmenopausal (defined as amenorrhea for ≥12 consecutive months prior to screening [day 1] without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. - females of childbearing potential: negative urine pregnancy test (human chorionic gonadotropin [hcg]) within 24 hours prior to each trial vaccination on day 1 and day 29. - females of childbearing potential must use highly effective methods of birth control from 2 weeks before the first administration of the trial vaccine until 3 months following the last administration. the following methods of birth control are considered highly effective when used consistently and correctly: - combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal or transdermal); - progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable or implantable); - intrauterine devices (iuds); - intrauterine hormone-releasing systems (iuss); - bilateral tubal occlusion; - vasectomized partner; - sexual abstinence (periodic abstinence [e.g., calendar, ovulation, symptothermal and post-ovulation methods] and withdrawal are not acceptable).

inclusion criteria: - male or female participants 18 years of age or older. - health care workers (hcws), employees or students in the clinical years. - provide written informed consent prior to initiation of any trial procedures. - expected compliance with protocol procedures and availability for clinical follow-up through the last planned visit. - females of non-childbearing potential defined as follows: surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy or hysterectomy) or postmenopausal (defined as amenorrhea for ≥12 consecutive months prior to screening [day 1] without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. - females of childbearing potential: negative urine pregnancy test (human chorionic gonadotropin [hcg]) within 24 hours prior to each trial vaccination on day 1 and day 29. - females of childbearing potential must use highly effective methods of birth control from 2 weeks before the first administration of the trial vaccine until 3 months following the last administration. the following methods of birth control are considered highly effective when used consistently and correctly: - combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal or transdermal); - progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable or implantable); - intrauterine devices (iuds); - intrauterine hormone-releasing systems (iuss); - bilateral tubal occlusion; - vasectomized partner; - sexual abstinence (periodic abstinence [e.g., calendar, ovulation, symptothermal and post-ovulation methods] and withdrawal are not acceptable).