The viruses that cause influenza change rapidly, making different strains coexist on the planet at any given time. Influenza vaccines are developed each year to protect people from the three strains expected to be most prevalent. All the viruses in the vaccine are killed, so it is not possible to get the flu from the vaccine. Most people achieve protection from influenza vaccine approximately 2 weeks after receiving the immunization. Immunization of high-risk people decreases many potential deaths from influenza.
Most people have no side effects from the influenza vaccine.
Unlike the swine flu vaccine of 1876, flu vaccines in recent years have shown no association with Guillain-Barre syndrome . As is the case with any drug or vaccine, there is a remote possibility that allergic, more serious reactions or even death may occur after receiving the flu shot. IF uncertain if the influenza vaccine should be delayed, withheld, or given to a specific person.