A leading cancer expert, who was described as a pioneer" in his field by Prince William, has died suddenly after receiving a routine yellow fever vaccination. Martin Gore, 67, died Thursday morning after receiving the vaccine. Professor Mel Greaves from the Institute of Cancer Research, described Gore as "a force of nature, very energetic, clear-thinking and compassionate." Gore's death casts light on the heightened risk associated with the yellow fever vaccine and the over-60 demographic. Typical side effects of the vaccine include headaches, muscle pain, mild fever and soreness at the injection site, according to the NHS. However, the vaccinations can, in rare circumstances, cause more severe side effects, including allergic reactions and problems affecting the brain or organs. The NHS estimates that these reactions occur less than 10 times for every million doses. The WHO reported that all cases of viscerotropic disease -- a rare but dangerous side effect of yellow fever vaccinations where an illness similar to wild-type yellow fever proliferates in multiple organs -- have occurred in primary vaccines, starting two to five days after vaccination. The Centers for Disease Control and Prevention -- the US government's health protection agency -- warns that viscerotropic disease can lead to multiple organ dysfunction syndrome or multi-organ failure and death in close to 60% of cases.