When people get the flu there is not drug to kill the virus. You take drugs such as aspirin, tylenol, or benadryl to ease the symptoms and to make the discomfort more bearable. The virus still has to run it s course. Not with a 106 temperature. He needs drugs to lower the fever and he need to rest for a least a week and maybe 2 weeks.
Several companies manufacture flu vaccine.
They are effective but not for a real long time. Most internal medicine experts consider that flu vaccine will only withstand a challenge for 2 months. One company says theirs is good for 6 months. The verdict is still out on that one. It is common practice for horse owners to give a 4 way shot in the springtime.