Flu vaccines are a critical component in the prevention of influenza, a contagious respiratory illness caused by influenza viruses. These vaccines are designed to protect individuals from the most common strains of the virus that are expected to circulate during the flu season. Each year, health organizations and scientists analyze data to predict which strains will be most prevalent, allowing manufacturers to develop vaccines that target these specific strains. The flu vaccine is typically administered as an injection, although a nasal spray version is also available for certain age groups.

As a collection of products, flu vaccines come in various formulations to cater to different age groups and health needs. There are standard-dose vaccines for the general population, high-dose vaccines for older adults who may need a stronger immune response, and adjuvanted vaccines that contain an added ingredient to boost the body's immune response. Additionally, there are cell-based and recombinant flu vaccines, which are produced using different technologies than the traditional egg-based method, offering alternatives for those with egg allergies.

Flu vaccines are recommended for almost everyone over the age of six months, with particular emphasis on high-risk groups such as young children, the elderly, pregnant women, and individuals with chronic health conditions. By receiving the flu vaccine, individuals not only protect themselves but also contribute to community immunity, reducing the overall spread of the virus. Annual vaccination is necessary because flu viruses constantly change, and immunity from the vaccine declines over time.