inclusion criteria: 1. adult male or non-pregnant, non-lactating female 1. part i: age 18-55 at the time of screening 2. part ii: age 56-74 years at the time of screening 3. part iii: age ≥ 75 years at the time of screening 2. pre-existing medical condition 1. part i and ii: free of clinically significant health problems, as determined by pertinent medical history and clinical examination at study screening 3. ability to understand and voluntarily sign the informed consent form. 4. ability to adhere to the study visit schedule and other protocol requirements. 5. female with child bearing potential (fcbp) and male volunteers with partners of childbearing potential, who are sexually active must agree to the use of two effective forms (at least one highly effective method) of contraception. this should be started from the signing of the informed consent and continue until three months after vaccination 6. postmenopausal or evidence of non-childbearing status. for women of childbearing potential: negative urine or serum pregnancy test within 7 days prior to study treatment. postmenopausal or evidence of non-childbearing status is defined as: * amenorrhoea for 1 year or more following cessation of exogenous hormonal treatments * luteinizing hormone (lh) and follicle stimulating hormone (fsh) levels in the post menopausal range for women under 50 7. be willing to minimize blood and body fluid exposure of others for 7 days after vaccination * use of effective barrier prophylaxis, such as latex condoms, during sexual intercourse * avoiding the sharing of needles, razors, or toothbrushes * avoiding open-mouth kissing * refrain from blood donation during the course of the study

inclusion criteria: 1. adult male or non-pregnant, non-lactating female 1. part i: age 18-55 at the time of screening 2. part ii: age 56-74 years at the time of screening 3. part iii: age ≥ 75 years at the time of screening 2. pre-existing medical condition 1. part i and ii: free of clinically significant health problems, as determined by pertinent medical history and clinical examination at study screening 3. ability to understand and voluntarily sign the informed consent form. 4. ability to adhere to the study visit schedule and other protocol requirements. 5. female with child bearing potential (fcbp) and male volunteers with partners of childbearing potential, who are sexually active must agree to the use of two effective forms (at least one highly effective method) of contraception. this should be started from the signing of the informed consent and continue until three months after vaccination 6. postmenopausal or evidence of non-childbearing status. for women of childbearing potential: negative urine or serum pregnancy test within 7 days prior to study treatment. postmenopausal or evidence of non-childbearing status is defined as: * amenorrhoea for 1 year or more following cessation of exogenous hormonal treatments * luteinizing hormone (lh) and follicle stimulating hormone (fsh) levels in the post menopausal range for women under 50 7. be willing to minimize blood and body fluid exposure of others for 7 days after vaccination * use of effective barrier prophylaxis, such as latex condoms, during sexual intercourse * avoiding the sharing of needles, razors, or toothbrushes * avoiding open-mouth kissing * refrain from blood donation during the course of the study

inclusion criteria: 1. adult male or non-pregnant, non-lactating female 1. part i: age 18-55 at the time of screening 2. part ii: age 56-74 years at the time of screening 3. part iii: age ≥ 75 years at the time of screening 2. pre-existing medical condition 1. part i and ii: free of clinically significant health problems, as determined by pertinent medical history and clinical examination at study screening 3. ability to understand and voluntarily sign the informed consent form. 4. ability to adhere to the study visit schedule and other protocol requirements. 5. female with child bearing potential (fcbp) and male volunteers with partners of childbearing potential, who are sexually active must agree to the use of two effective forms (at least one highly effective method) of contraception. this should be started from the signing of the informed consent and continue until three months after vaccination 6. postmenopausal or evidence of non-childbearing status. for women of childbearing potential: negative urine or serum pregnancy test within 7 days prior to study treatment. postmenopausal or evidence of non-childbearing status is defined as: - amenorrhoea for 1 year or more following cessation of exogenous hormonal treatments - luteinizing hormone (lh) and follicle stimulating hormone (fsh) levels in the post menopausal range for women under 50 7. be willing to minimize blood and body fluid exposure of others for 7 days after vaccination - use of effective barrier prophylaxis, such as latex condoms, during sexual intercourse - avoiding the sharing of needles, razors, or toothbrushes - avoiding open-mouth kissing - refrain from blood donation during the course of the study

inclusion criteria: 1. adult male or non-pregnant, non-lactating female 1. part i: age 18-55 at the time of screening 2. part ii: age 56-74 years at the time of screening 3. part iii: age ≥ 75 years at the time of screening 2. pre-existing medical condition 1. part i and ii: free of clinically significant health problems, as determined by pertinent medical history and clinical examination at study screening 3. ability to understand and voluntarily sign the informed consent form. 4. ability to adhere to the study visit schedule and other protocol requirements. 5. female with child bearing potential (fcbp) and male volunteers with partners of childbearing potential, who are sexually active must agree to the use of two effective forms (at least one highly effective method) of contraception. this should be started from the signing of the informed consent and continue until three months after vaccination 6. postmenopausal or evidence of non-childbearing status. for women of childbearing potential: negative urine or serum pregnancy test within 7 days prior to study treatment. postmenopausal or evidence of non-childbearing status is defined as: - amenorrhoea for 1 year or more following cessation of exogenous hormonal treatments - luteinizing hormone (lh) and follicle stimulating hormone (fsh) levels in the post menopausal range for women under 50 7. be willing to minimize blood and body fluid exposure of others for 7 days after vaccination - use of effective barrier prophylaxis, such as latex condoms, during sexual intercourse - avoiding the sharing of needles, razors, or toothbrushes - avoiding open-mouth kissing - refrain from blood donation during the course of the study