A flu immunization is a vaccine given to people to protect them from one variation or several variations of the influenza virus. The influenza virus, more commonly known as the flu virus, is a virus that affects up to twenty percent of the global population. In thousands of cases each year, it is even fatal. A flu vaccine consists of one or several strains of the flu virus in a dead or otherwise disabled state; this exposure allows the immune system to develop an immunity to the virus. Typically, a flu immunization is administered through a shot, though some are administered through a nasal spray.
A flu immunization tends to last for about one year because the flu virus is extremely variable and adaptable. Many people choose to get vaccinated just prior to the flu season, which varies based on location and usually occurs during the coldest months of the year. In the United States, for example, the flu season starts in September or October and ends in February or March. During a particularly bad flu season, it is not uncommon for abnormally large numbers of people to try to get vaccinated, and supplies of the vaccine can run low. As such, it is important to get a flu immunization early in the flu season.
There are many factors that determine one's risk of getting the flu and, accordingly, whether or not one should get a flu immunization. Children and young adults generally are at high risk, so those between the ages of six months and nineteen years old are often advised to get the flu vaccine. Health care workers and others who work closely with large groups of other people are also good candidates to get the flu immunization, as the risk of transmitting the flu virus in such conditions is high.
There are some people who should not, under any conditions, get the flu vaccine. Those who are allergic to chicken eggs typically will have a negative reaction to the vaccine because it is made using chicken eggs; these people should not receive flu immunization. People who are suffering from some form of illness or infection should also avoid the vaccination; it is possible that a weakened strain of the flu from the vaccine could infiltrate the individual's immune system.
Though normally administered in a shot form, the flu immunization can also come in the form of a nasal spray. This was true of the vaccine meant to protect against the 2009 H1N1 flu virus. The spray is sometimes called LAIV for Live Attenuated Influenza Vaccine. The spray contains live but severely weakened viruses that can not grow and cause damage at normal body temperatures.