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Another vaccine approach was tested in a large trial called STEP.This trial tested a vaccine designed to encourage cellular immune responses.Vaccine approaches that have been successful against other viruses – killed or weakened versions of a virus – have not proved suitable in the case of HIV, owing to the risk that the viral material used in the vaccine will integrate into human cells and eventually lead to new virus replication.Another challenge is that HIV is divided into families, or sub-types, that predominate in different parts of the world.
The trial found that AIDSVAX was no more effective than a placebo, or dummy vaccine, in preventing HIV infection.
An alternative approach designed to stimulate both cellular immunity and antibody production was tested in the RV144 trial.
This study used two vaccines in what is called a ‘prime-boost’ approach.
A vaccine will need to be effective against all sub-types, or different vaccines must be developed against different sub-types.
Most vaccines work by stimulating one part of the immune response to produce antibodies against an infectious agent.
This page summarises the current state of research and the challenges facing scientists.