The drive to develop a vaccine to prevent HIV infection is one of the most heroic endeavours in the history of medical research. No other virus has received such scientific attention or so much funding for vaccine development – $759m last year alone from public, commercial and charitable sources according to the International Aids Vaccine Initiative (Iavi).

Twenty years after research started, an effective and widely available HIV vaccine is still at least another decade away. “Two or three years ago there was a lot of discouragement in the scientific community but now there is a new sense of optimism about Aids vaccine development,” says Seth Berkley, president of New York-based Iavi.