[Principled]

They don't make the vaccine until after they've identified what strain they think is coming each year. So even if you get a flu shot, you may be doomed if it's the wrong strain.

You could always take last year's shot, but that would be akin to taking cough medicine for arthritis...???

Scientists make a different vaccine every year because the strains of flu viruses change from year to year. Nine to 10 months before the flu season begins, they prepare a new vaccine made from inactivated (killed) flu viruses. Because the viruses are killed, they cannot cause infections. The vaccine preparation is based on the strains of the flu viruses that are in circulation at the time. It includes those A and B viruses (see section below on types of flu viruses) expected to circulate the following winter.

Sometimes, an unpredicted new strain may appear after the vaccine has been made and distributed to health care providers and clinics. Because of this, even if you do get the flu vaccine, you still may get infected. If you do get infected, however, the disease usually is milder because the vaccine still will give you some protection.

From this link

[philman_36]

Thanks for the link and info. I feel more informed now and I learned something new.

[philman_36]

And thanks for some more keywords...
From the CDC...Questions & Answers: Flu Shot
The flu shot is an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. It contains three influenza viruses. The three vaccine strains – one A (H3N2) virus, one A (H1N1) virus, and one B virus – are representative of the influenza vaccine strains recommended for that year.