Another issue that can lead researchers not to take part is whether the researcher would stand to gain any benefit from taking part in the experiment. It is an ethical principle that volunteers must stand to gain some benefit from the research, even if that is only a remote future possibility of treatment being found for a disease that they only have a small chance of contracting. Tests on experimental drugs are sometimes conducted on sufferers of an untreatable condition. If the researcher does not have that condition then there can be no possible benefit to them personally. For instance, Ronald C. Desrosiers in responding to why he did not test an AIDS vaccine he was developing on himself said that he was not at risk of AIDS so could not possibly benefit. Against that, the early stages of testing a new drug are usually focused merely on the safety of the substance, rather than any benefits it may have. Healthy individuals are required for this stage, not volunteers suffering from the target condition, so if the researcher is healthy, he or she is a potential candidate for testing. An issue peculiar to AIDS vaccine research is that the test will leave HIV antibodies in the volunteers blood, causing the person to show HIV positive when tested even if they have never been in contact with an HIV carrier. This could cause a number of social problems for the volunteers (including any self-testers) such as issues with life insurance.