Many people assume that if they’ve had the flu recently, they can’t get it again — and thus don’t need to get the vaccine, Perl says. That’s not the case because flu infection can happen from more than one strain of virus.
“In any flu season, there’s usually both Type A and Type B influenza in circulation,” Perl tells WebMD. Both can cause the flu. It’s quite possible that you could get infected with one type and then the other.
So if you’ve already had the flu, you should still get the vaccine. “Otherwise, you could be sick and unhappy twice,” Perl says.