According to Business Insider, how effective the flu vaccine is will vary from year to year.
In fact, it can range anywhere from 20% to 60% in efficacy.
That's because sometimes, the viral strains that end up in the flu vaccine don't match the viral strains that make people sick.
The Centers for Disease Control and Prevention says it's too soon to tell how effective this year's flu vaccine will be.
However, it encourages everyone who is eligible to get a flu jab nevertheless.
The nasal-spray vaccine can be an ideal alternative for people afraid of getting the flu shot.
There is also a high-dose flu shot that contains more virus particles than the regular shot.
This inoculation is for people aged 65 and older whose immune system may not be as strong.