evidence: Flu shot: Your best bet for avoiding influenza [...] No, the flu vaccine can't give you the flu. And the flu vaccine does not make you more likely to get another respiratory infection based on available evidence. [...] - Mismatched flu viruses. In some years, the influenza viruses used for the vaccine don't match the viruses spreading during the flu season. If this occurs, your flu shot will be less effective. But it may still offer some protection.