The flu vaccine (administered as a shot or a nasal spray) is made of a combination of the different types of influenza viruses that research indicates will be most common during the upcoming season. For each type of influenza, there are numerous specific viruses that can be selected for use in the vaccine. The vaccine works by introducing small amounts of these influenza viruses to the body. Their presence stimulates the immune system to create antibodies against these specific viruses that help protect the individual from becoming infected with them. Each year, the specific viruses used in the vaccine will vary. Based on what you know of evolution, why might this be the case

This happens because viruses mutate and vary according to the environment they face. That is why different strains occur and appear every day, which must be updated in the vaccines, in order to have immunity up to date and keep up with the viral mutation without making us sick.

Explanation:

Viruses are acellular structures that do not have their own metabolism or replication method, it is because they must dominate and invade the human body so that its DNA or RNA is coupled to the human and this uses the human machinery to be able to replicate.

On the other hand, as infections occur and viruses appear, they can associate with bacteria forming bacteriophages, they can mutate within an organism that is infected by more than one viral infection and they can even adopt retrovirus mechanisms, which day by day. These new viruses are called as new strains, which evolve and will have to be coupled with vaccines.

Vaccines are a method of natural ACTIVE immunity, that is, part of the virus is inoculated, so that it generates the formation of a specific antibody in the body.

true, i don't really know what you're asking but from the info you provided im guessing the answer is true.