Pharmacies across the country are stocking flu shots and encouraging people to get theirs early. But experts say, don't rush. If you get your flu shot too early, it can become ineffective before the flu season is over. According to a series of studies released last year, vaccinations are not lasting as long as doctors thought. After 3 or 4 months, the effectiveness of the flu shot dropped dramatically. Those who got their flu shots early were virtually unprotected by February. But doctors say, if you already got your flu shot this season don't panic. Expects say the best time to get the shot is soon, just a few weeks from now, in early fall, to be protected for the bulk of flu season.