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, which is recommended to travelers visiting sub-Saharan Africa, most of South America, and parts of Central American and the Caribbean.
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London's Royal Marsden NHS Foundation Trust, where Gore worked for more than 30 years, expressed its "deep sadness" following the announcement of his death.
"Martin was at the heart of The Royal Marsden's life and work in research, treatment and the training of our new oncologists," the hospital said in a statement. "His contribution as medical director for 10 years, a trustee of The Royal Marsden Cancer Charity, and as a clinician is unparalleled."
Professor Mel Greaves from the Institute of Cancer Research, described Gore as "a force of nature, very energetic, clear-thinking and compassionate." While Allyson Kate, president of the charity Ovarian Cancer Action, said: "He was a giant in the field and a humorous colleague. There is no doubt that professor Gore improved the lives of many. He will be greatly missed."
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.
Martin Goodier, assistant professor in immunology at the London School of Hygiene and Tropical Medicine, nevertheless noted that severe reactions are rare, and the vaccine remains "extremely effective."
"The yellow fever vaccine is extremely effective in protection against this infection and has been used worldwide for many years," he told CNN. "Because of the widespread use of the vaccine we can say with certainty that such adverse events are rare. The benefits to health of vaccination far outweigh any potential risk."
The WHO also told CNN: "While the risk of adverse effects is higher in persons aged over 60 years, the overall risk remains low." The organization nevertheless noted that a "risk-benefit assessment" for individuals aged over 60 should be performed, taking into account the risk of acquiring the disease.
Jonathan Ball, professor of molecular virology at the University of Nottingham, added: "Individuals are advised to have the vaccine if they are traveling to tropical and sub-tropical places where yellow fever is known or suspected to exist."
He noted that while the vaccine is "very safe," serious side effects have a greater risk of developing in the over-60s and in very young infants. Notably, he pointed to reports which suggest that the risk of developing "vaccine-associated viscerotropic disease" increase to around 12 cases per million vaccine doses used, up from three cases per million in the under-60 age group.
However, he stated that it still "makes sense" for individuals in "at risk" age groups to get vaccinated if the risk of exposure to the virus is very high.
Gore was an oncologist for more than 35 years, and first joined the Royal Marsden in 1978 as a senior house officer. He was appointed medical director of the trust in 2006, and held the role for 10 years until he stepped down in January 2016.
His other notable roles include acting as the chairman of the Gene Therapy Advisory Committee at the Department of Health between 2006 and 2012, being a senior investigator at the National Institute for Health Research between 2008 and 2011, and being appointed commissioner of the Commission on Human Medicines at the Medicines and Healthcare Products Regulatory Agency.
Gore also received a lifetime achievement award in 2015 from Prince William, who is president of the Royal Marsden. Commenting on Gore's contribution at the time, the Prince said: "I've found Martin a source of inspiration -- his infectious enthusiasm and passion for his work, and his obvious compassion and kindness for his patients, their family and friends, reinforces my knowledge that the Royal Marsden is a truly special place.
"He's one of the pioneers of 20th century cancer care, and a friend, colleague and trusted doctor to many."