Joe Cohen has dedicated almost half of his life to developing a malaria vaccine.
Now 70, he may finally see the fruits of a project he started in 1987 when he was asked to lead a malaria research unit at the then SmithKline & French.
His has been a story of persistent scientific endeavour. Dr Cohen's research unit has survived two major mergers and a succession of chief executives despite its relatively slow progress: most vaccines take 10 - 15 years to develop.
His research team, which has numbered hundreds over the years, is not alone in being confounded by the complexity of the malaria parasite, which produces more than 5,000 proteins over its lifetime. This poses a challenge to scientists in figuring out which of those proteins to imitate to trigger an immune response in the body, providing future protection from the parasite.
In the late 1980s scientists decoded a particular protein found in the malaria vaccine, known as circumsporozoite (CS), sparking a wave of research into its potential as a vaccine.
Various attempts at using the protein in a vaccine failed, until Dr Cohen's team hit upon what he calls a "fundamental insight” which would inform their work for the next decade. They realised combining part of an already-existing Hepatitis B vaccine with the CS protein could create a successful shot.
The first tests, on US adults in the early 1990s, proved the concept worked, setting in motion a series of trials that have shown how effective the vaccine could be across sub-Saharan Africa, where malaria is most prevalent.
But although the team could see their product had great potential as early as 1997, it has taken another 16 years to amass enough evidence that it is effective across age groups, in different settings, and for a meaningful length of time.
Dr Cohen says the programme has suffered no major setbacks since it started trialling the vaccine in Africa in the late 1990s. But recent findings have shown the vaccine may not be as effective as first hoped.
In March, trial results showed the vaccine’s effectiveness waned over the course of four years. The findings released in October indicated that the shot offers far less protection to very small babies, for reasons which are still largely unknown.
But the sheer scale of malaria, which killed 660,000 in 2010, means the vaccine does not need to be fully effective to make a huge difference.
The economic implications are also profound. Studies suggest a 10pc reduction in malaria could add 0.3 percentage points to GDP of countries which suffer from a high incidence of the disease.