Figure 2.

Vaccination strategies targeting adaptive or innate immune memory. (A) Classical vaccines initially induce a slow adaptive immune response. During this primary response, however, adaptive immune memory is raised, allowing for a more rapid and stronger secondary response upon encounter of the targeted pathogen. This protection is very long-lived, but is limited to the antigens present in the vaccine. (B) Most vaccines also induce a very rapid innate immune response. During this primary response, some vaccines also “train” innate immune cells, allowing for a stronger secondary innate response against pathogens. One advantage of this innate immune memory is the non-specificity of the secondary response, which could potentially lead to broadly cross-protective vaccines. A potential disadvantage would be the relatively shorter time window of protection.