I remember reading that the NHS leaves the official jab formulation until the last minute because they don't know which strain they are up against. Do they modify the jab as time goes by, or do they have a cut off date and say "right, that's it?" If it's the former, isn't it better to bide one's time, assuming you don't die of flu in the meanwhile?
I'm sure
@User has the answer.
Lifted from the NHS Choices site:-
"Flu vaccine is the best protection we have against an unpredictable virus that can cause unpleasant illness in children and severe illness and death among at-risk groups, including older people, pregnant women and those with an underlying medical health condition.
Studies have shown that the flu jab will help prevent you getting the flu. It won't stop all flu viruses and the level of protection may vary, so it's not a 100% guarantee that you'll be flu-free, but if you do get flu after vaccination it's likely to be milder and shorter-lived than it would otherwise have been.
There is also evidence to suggest that the flu jab can reduce your risk of
having a stroke.
Over time, protection from the injected flu vaccine gradually decreases and flu strains often change. So new flu vaccines are produced each year which is why people advised to have the flu jab need it every year too."
