Vaccines or immunizations like flu shots are types of vaccines. In order to develop immunity to specific diseases, you need not become ill or infected first. As soon as you're vaccinated, you're protected from the condition that the vaccine targets. Vaccines also prevent or slow the spread of infectious diseases between communities, not just individuals. The flu vaccine must be updated every year, unlike the many pediatric vaccines given in the early years of a child's life. Each year, a new variant of influenza mutates and circulates, so the vaccine has to be reformulated. Studies and information are used by vaccine manufacturers to determine which variants are likely to dominate during a particular flu season. There is no risk associated with vaccinations, including the flu vaccine. A flu shot is the most effective way to reduce your risk of getting the flu or spreading it to others each year. Due to the dangers flu poses to very young children, children under five should be vaccinated against it yearly. When young children come down with the flu, they are at a greater risk of developing serious complications. As a result of the flu, children younger than five years of age are at risk of hospitalization, as well as pneumonia, dehydration, and brain dysfunction in worst-case scenarios.