ericka edwards has more. >> reporter: just under half of all americans got the flu vaccine last year. some doctors say common myths about the vaccine may be one reason why many choose not to get a flu shot. one of the most common, you can catch the flu from the vaccine. scientists say absolutely false. >> it will never give you the you can get muscle aches and fever after the flu shot but that just means it is working. it doesn't mean it is giving you the flu. >> if you get sick after a shot doctors say it is likely a different virus, not true influenza. >> the flu virus mutates every year. it's not the same virus this year that was there last year. you need a new shot every year to get protection. >> we recommend that everyone over six months get a flu shot this year and every year. >> last year's vaccine proved to be about 50% effective. although flu is unpredictable, cdc is hopeful this year's vaccine is a good match for the upcoming flu season. >> were you nodding your head? >> i have heard all of that. >> this year saying it is not shown protective against the the flu virus. >> y