Vaccines???

Question

why do they have to develop a new vaccine every year? Why can't they keep using the same one?

Answer 1

Because some viruses evolve to evade the immune cells that the vaccines generate.

Influenza, for example, evolves new strains every year.

In contrast, essentially the same polio vaccine has been used for decades.

Answer 2

The influenza virus has a high mutation rate, which requires new vaccines every year. As the virus emerges in asia, they attmept to identify the most prominent form, and develop a vaccine accordingly.