Psychological influences not only influence the effectiveness of the flu vaccine, but directly impact the immune system itself. For example, studies show that loneliness appears to have a significant impact on physical health, being linked detrimentally to worse sleep and immune stress responses over time in the elderly. In college students, elevated levels of loneliness throughout the semester and small social networks are independently associated with poorer antibody response to the influenza vaccine. Those with both high levels of loneliness and a small social network had the lowest antibody response. Individuals who chronically experience social isolation actually change the genes so that more pro-inflammatory activity predominates.
Luanaigh C.O., Lawlor B.A., Loneliness and the health of older people. Int J Geriatr Psychiatry, 23(12):1213-21, 2008.
Pressman S.D., et al, Loneliness, social network size, and immune response to influenza vaccination in college freshmen. Health Psychol, 24(3):297-306, 2005.
Cole, S.W., et al, Social regulation of gene expression in human leukocytes. Genome Biol, 8(9):R189, 2007.