FluMist, known as Fluenz in the UK, is a live attenuated vaccine delivered nasally. The risks are significant. What may be even more important is that, as a live vaccine, people who receive it shed the virus. That means they are infectious after getting the vaccine!
So how does this protect the elderly? If they aren’t in contact with a child, then there’s no risk of getting flu from them, so there’s no reason for the child to get the vaccine. If they are in contact with a child, then a recently vaccinated child would be likely to transmit the flu to them!
When Flu Mist was first introduced in the US in 2003, Dr Sherry Tenpenny wrote:
"FluMist contains live (attenuated) influenza viruses that replicate in the nasopharynx of the vaccine recipient. The most common side effects include "cough, runny nose/nasal congestion, irritability, headaches, chills, muscle aches and fever > 100° F." These symptoms are nearly identical to those the flu vaccine is designed to prevent."