iii. Social and legal marginalization of groups from which participants are drawn e.g. sex workers iv. Limited availability, access and sustainability of health care and treatment options v. Limited ability of individuals or groups to understand the research process vi. Limited ability of participants to freely give informed consent on account of gender, illiteracy and other social and legal factors vii. Lack of a meaningful national or local ethical review 8. Guiding principal 8: Clinical trials. As phases 1, 11, and 111 in the clinical trials development of a prevention or treatment vaccine, all have their particular scientific requirements and specific ethical challenges, the choice of study population for each trial phase should be justified in advance in both scientific and ethical terms in all cases, regardless of where the study population is found. Generally, early clinical phases of HIV vaccine research should be conducted in populations that are less vulnerable to harm and exploitation. • Experimental HIV vaccine should be directed towards a viral strain that exists in country • Establishing a vaccine development programme that entails the conduct of some, most or all of its clinical trial components in a community that is relatively vulnerable to harm or exploitation is ethically justified if: i. The vaccine is anticipated to be effective against a strain of HIV that is an important public health problem in the country 23