I've had the flu shot each year for the last 8 years and find the only reaction is a sore arm, where it is injected for about a day. This is the common reaction from all those I know who have had it.
There was one year when my arm was not sore and I wonder if the vaccine was ineffective. The vaccine is meant to be stored in a fridge.
My mother, who has always been very cautious with medicines, said to me that she didn't think it was a good idea to have the flu shot if you were younger and didn't not have an immune deficiency. Her reasoning was that it is better to allow the body to develop it's own immune system to be stronger. Having the flu would allow this to happen. I can't fault her reasoning.
For those in Australia, the we could get the flu vaccine injection at the chemist for the first time this year. It was available to be done at the chemist several weeks before the Doctor's surgeries had a supply. I tried to find out why and if the vaccine was being provided by two different manufacturers. The pharmacist couldn't tell me (which I find incredible as he purchases these supplies),
Not long ago, they were encouraging infants and children to be immunized which I don't believe is necessary and possible not a good thing. There was an alarming amount of babies and young children that died as a direct result. The Health authority advised that there was a problem with the vaccine and it needed further development. It has taken several years to come up with a safer vaccine. Whether they have or not, I don't know, it could be that parents have stopped having their kids injected.
The number of people hospitalized resulting from the flu seems to be on the increase and the flu seems to be more severe. This may be due to reporters trying to make headlines or propaganda. But I do think the flu is more severe.