Get your flu shot in September or October, especially if you are 65 or older
Added
CDC says September and October are generally good times for most people who need one dose, ideally by the end of October. Adults 65 and older should usually avoid July or August shots because protection can wane. For people 65+, CDC and ACIP preferentially recommend a higher-dose, recombinant, or adjuvanted flu vaccine when available; if none of those is on hand, get another age-appropriate inactivated shot rather than skip it.
The result
Result: CDC: people 65+ face higher risk of serious flu complications; preferential vaccines are high-dose inactivated, recombinant, or adjuvanted inactivated. Timing guidance favors September–October; avoid early (July–August) vaccination for most older adults unless later vaccination may not be possible.
Source
Centers for Disease Control and Prevention (CDC) (opens the original source in a new tab). Check it for the latest numbers before you act.