Participants in AIDS vaccine trials may produce antibodies to parts of the HIV virus. This can cause problems for them later as these immune responses can make them appear to test positive for HIV although they are not infected. A consequence of this positive result is that they could face potential discrimination when applying for insurance or future employment and could have difficulty with obtaining travel visas or going through immigration. People with a positive HIV test are also prohibited from donating blood and can face social stigmatization. These potential difficulties are discussed with each volunteer during the informed consent process before the vaccine trial begins.
Vax Online Primer