Since the vaccine takes about 2 weeks to begin its effect. A later vaccination can also provide substantial protection. The influenza shot is covered by Medicare and some other health plans. At the first sign of influenza symptoms see your doctor. Some doctors use a new rapid point of care test given in a doctors office which can diagnose all strains of influenza A and B. Many physicians now use antiviral medications when they are confident of the diagnosis.
Most people have little or no reaction to the vaccine.
One in four might have a swollen, red, tender area where the vaccination was given. A much smaller number, probably more children than adults, might also develop a slight fever within 24 hours. They may have chills or a headache, or feel a little sick. People who already have a respiratory disease may find their symptoms worsened. Usually none of these reactions lasts for more than a few days.