The pig's immune system is a complex network. It is responsible for recognizing and repelling pathogens, which helps provide protection against infection. The immune system controls pathogens in three ways:

  • Innate immunity
  • Passive immunity
  • Adaptive immunity

Adaptive Immunity

This response system reacts when exposed to pathogens and vaccine antigens, providing long-term protection against future infection by the same invading pathogen. It functions throughout life.

  • Cell-mediated immune (CMI) response
    1. Produces specific white blood cells (T lymphocytes) that facilitate antibody production and help fight and clear infected cells and protect non-infected cells
  • Humoral immune response
    1. Produces antibodies that flow through body fluids and mucosal surfaces to help stop infection

Response to infection or vaccination

  • Innate system (red & dark green) responds immediately for a short time in generally a non-specific way
  • Cell-mediated (yellow) portion of the adaptive response occurs reasonably quickly with the production of white blood cells to kill pathogens and help the humoral response
  • After 7-10 days, antibodies (blue) from the humoral component of the adaptive immune system begin to appear

Vaccination response

The first peak represents the primary response of the humoral system, which occurs after the first dose of vaccine or after the first time the system is exposed to a pathogen. With one-dose vaccines, the primary response lasts longer.

Anamnestic response occurs after the second dose of vaccine or after additional times the pig's immune system is exposed to a pathogen. In one-dose vaccines, exposure to the pathogen provides the booster response.


Killed vaccines need an adjuvant to improve efficacy and boost immunity and immune response. Adjuvants trick the immune system into thinking the antigen is really live, which causes the immune system to react at a much greater level.