One factor that may affect safety and immunogenicity to an HIV vaccine is the route of vaccine administration. Administration into the skin (intradermal) or subcutaneous tissue may be more immunogenic or provide a different pattern of immune responses than administration by the intramuscular route. Previous studies with other preventive vaccines suggest that the resulting immunogenicity following intradermal or subcutaneous vaccine administration is comparable or better than immunogenicity observed following intramuscular administration. Increased immunogenicity though use of a particular route will likely result in greater demonstrated efficacy, requiring fewer or lower doses of vaccine to elicit a sufficient immune response.