Overview

Immunization is designed to stimulate immune responses against antigens of infectious agents (e.g. bacteria or viruses) and generate specific immunological memory such that successfully immunized individuals, when exposed to the infectious agent later in life, will respond with protective immunity. When this response was first being elucidated, the cellular and molecular interactions involving T and B lymphocytes (main cells of the immune system), antibodies (antigen-specific effector molecules) and cytokines (immune regulatory hormones) were thought to operate virtually autonomously within the body, influenced predominantly by the internal state of the immune network and the characteristics of antigens (foreign shapes derived from infectious agents). However, individual differences in susceptibility to infection and effectiveness of immunity following vaccination, led to exploration of non-physiological factors.

Research using laboratory animals demonstrated that ‘lifestyle’ factors such as overcrowding (Edwards & Dean, 1977) and exposure to physically stressful conditions (Sheridan, 1998) reduced immune responses to immunization often to the point that the animals become susceptible to infection. Such studies extended into the human arena have confirmed that many aspects of human psychology affect immune responses to vaccination and should be considered as significant factors in vaccine effectiveness.

Research evidence

Stress and immunization

When healthy women were immunized with a novel antigen, keyhole limpet haemocyanin (KLH), those reporting more stressful events had lower baseline and post-immunization lymphocyte proliferation (Snyder et al., 1993) and anti-KLH antibody levels in their blood, while those reporting more social support had higher responses (Snyder et al., 1990; Snyder et al., 1993).