Influenza virus causes flu which is a contagious respiratory illness that infects nose, throat and lungs. It can mild or severe and sometimes may lead to death. Flu vaccination every year can help in preventing flu. However, this can be deadly, especially in high-risk groups. Aged population, pregnant women and people with one or more chronic disease or with weak immune systems are at high risk. Influenza vaccines/flu shots protect against the four influenza virusesâ€ subtypes that are most common. Most of the influenza vaccines are â€œflu shotsâ€ given with a needle, usually in the arm, but nasal spray flu vaccine are also available...Read more