By Sam Blanchard Health Reporter For Mailonline
Published: 14:51 BST, 18 April 2019 | Updated: 15:21 BST, 18 April 2019
Two people in the UK have died after being given a vaccine to protect against the potentially fatal yellow fever.
The tropical illness is spread by mosquitoes and found in Africa, South and Central America, and the Caribbean, so the jab is recommended for people travelling to those areas.
But in extremely rare cases – approximately one in a million – the vaccine can trigger viscerotropic disease, which can be deadly.
Both the unidentified victims were in categories of people who shouldn't always be given the vaccine – one was aged over 60 and the other had had their thymus gland removed.
Health chiefs have now warned medics to check it's safe to give their patient the jab, which can cost around £60 on the NHS, before they do so.
Two patients in the UK have died after being given the yellow fever travel vaccine, which went on to cause a disease which can lead to multiple organ failure (stock image)
The UK's Medicines and Healthcare products Regulatory Agency (MHRA) revealed the cases in a report this week.
Both patients died 'shortly' after receiving the vaccine because of yellow fever vaccine-associated viscerotropic disease (YEL-AVD).
One of them was 67 years old – the life-saving jab is not recommended for people over the age of 60, according to the NHS.
It's also not recommended for people who have had surgery to remove their thymus gland, a gland in the chest which is part of the immune system.
The other victim, who was in their 40s, had had this operation.
Live vaccines, such as the one given to protect against yellow fever, work by injecting a weakened but still living form of the virus into the body.
The purpose of this is to train the body how to make the right antibodies to fight off the virus, so it can remember how to do so in future.
However, if someone's immune system is