@deni The virus contained in the flu injection is dead. It cannot infect you with the flu. The nasal spray vaccine contains a live, but weakened virus. It is not recommended for people with weakened immune systems, but for average people, it will not infect them with the flu.
The vaccine is not 100% effective, so of course people who get it still get the flu sometimes. But it decreases the likelihood of getting the flu.
A lot of people write it off due to anecdotal experiences with getting the flu after getting vaccinated. This is erroneous because it is still possible to get the flu after getting the vaccine. In another recent thread I believe it was stated that this year’s vaccine is about 60% effective (I didn’t fact check this claim). So 40% of people who get the vaccine and are exposed to the flu will still get it. That’s better than 100%.