There are also flu vaccines that protect against four strains of the flu virus (quadrivalent vaccines), which provide protection from the same strains as those mentioned above as well as another B virus.

There are several types of vaccines within these categories, as outlined by Flu.gov:

●     Standard-dose trivalent shots (IIV3)/Quadrivalent flu shot: These vaccines are manufactured using virus cultures grown in eggs. There are different versions for people of different ages. Shots are available for those as young as six months of age and older.

●     Intradermal trivalent shots: These vaccines, which are approved for people aged 18 to 64, are injected into the skin, not the muscle, thus allowing for use of a smaller needle.

●     High-dose trivalent shot: This vaccine is approved for people 65 and older. Those in this age bracket are a higher risk of serious complications from the flu virus.

●     Trivalent shot containing virus grown in cell culture: This injection is approved for people ages 18 and up.

●     Recombinant egg-free trivalent shot: This injection is also available for people who are 18 to 49.

●     Quadrivalent nasal spray vaccine: This form of the vaccine is approved for people two to 49 years old and recommended preferentially for healthy children two to eight years old, unless there is an underlying medical condition that would predispose them to flu complications.

Beginning with the 2014-15 flu season, the CDC began recommending the use of the quadrivalent nasal spray vaccine in healthy children between the ages of two and eight, when immediately available, and to get an injection rather than delay getting the vaccine. Most important, the CDC advise all people six months of age and older to get a flu vaccine each year, except people who are deemed “high risk for developing flu-related complications.”