I'll answer what i can
Answer:
Its recommended because it can help fight the flu if you get it
It affects the immune system by training it to target the flu, and gain resistance to it
The best time is during cold, due to the fact that cold helps the virus (heat kills some viruses)
depending on the person depends on whether its effective or not.
<h2><u>Recommended for taking it, i do not know. Sorry for the missing answer.</u></h2>
Its important for the CDC to update it every year because the flu isn't always the same, and can adapt to the shot to where it has no effect.
