This trial studies the safety and immunogenicity of a HIV clade B'/C DNA vaccine followed by recombinant vaccinia virus rTV boost in HIV-uninfected healthy volunteers at low or high risk of HIV infection. In addition, the effect of different intervals of the prime-boost will be studied.

Inclusion Criteria:

• Willing to be followed for the planned duration of the study, and receive intravenous blood collection and sample storage in the 16~20 months after first vaccination;
• Understand and agree with the content of informed consent;
• Volunteers at low risk of HIV infection, or high-risk men who have sex with men (MSM）, who had have oral sex or anal sex with another man in the past 6 months ;
• Willing to be tested for HIV and syphilis;
• Before 2 weeks of the first vaccination and after 12 months of the last vaccination, willing to use an effective method of contraception with sexual partner. Female subjects are willing to undergo urine pregnancy test before each vaccination and at the follow-up visit.

Exclusion Criteria:

• Have close contact with people who are pregnant or lactating in the one month after vaccination of rTV vaccine;

• Have listed diseases or medical history:

  • Have innate or acquired immune deficiency disease or have close contact with patients suffering from the above-mentioned diseases within 1 month of rTV vaccination;
  • Need treatment affecting immunization, e.g. use corticosteroids for more than 2 weeks or use immunosuppressives, e.g. alkylating, anti-metabolite or radiotherapy, etc.; or have close contact with patients suffering from the above-mentioned diseases within 1 month of rTV vaccination;
  • Suffering from immunosuppressive diseases such as cancer, organ or stem cell transplants, non-agammaglobulinemia, etc.; or have close contact with patients suffering from the above-mentioned diseases within 1 month of rTV vaccination;
  • Past or current suffering from eczema or atopic dermatitis; currently suffering from diseases that cause skin damage such as: burns, scald, chicken pox, impetigo, shingles, psoriasis, etc.; or have close contact with patients suffering from the above-mentioned diseases within 1 month of rTV vaccination;
  • Past or current high blood pressure, heart disease, diabetes, thyroid disease, asthma, angioedema, asplenia syndrome, mental illness, epilepsy, severe anemia, leukopenia and thrombocytopenia, etc.;
  • History of syncope after vaccination or allergies;
  • Currently suffering from acute infectious diseases and febrile diseases；

• The following circumstances are:

  • Live attenuated vaccine received within 2 months or other vaccine within 2 weeks prior to enrollment;
  • Immunoglobin or blood products received within 4 months prior to enrollment;
  • Participation in another trial of a medicinal product, completed less than 30 days prior to enrollment;
  • Drug abuse, alcoholism, heavy smokers；

• The following laboratory test abnormalities, except for the results that are assessed by researchers as being no clinical significance：

  • HIV diagnostic assay positive or suspicious, HIV RNA diagnostic assay positive;
  • Anti-DNA antibody or anti-nuclear antibody positive;
  • Other laboratory test abnormalities;

• Not complying with study protocol or not obtaining informed consent because of medical, spiritual, social, occupational, and/or other reasons.