Psychological variables as predictors of rubella antibody titers and fatigue--a prospective, double blind study.

When exposed to infectious pathogens, human beings manifest variability in the incidence and severity of infection. This variability may partly depend on psychological variables, which have long been thought to contribute to the predisposition, onset, and course of various physical illnesses, including infectious diseases. The objective of the study was to investigate the predictive value of several personality and other psychological variables on antibody titers and fatigue following a specific viral infection. Subjects were divided into a seronegative group (not immune prior to vaccination) (N = 60) and a seropositive group (immune prior to vaccination) (N = 180), based on antibody titers to rubella before and 10.5 weeks after vaccination with live-attenuated rubella virus. Questionnaires assessing externalizing, internalizing, self-esteem, neuroticism, and fatigue-related symptoms were administered to the subjects before vaccination. Fatigue-related symptoms were re-evaluated 10 weeks post vaccination. In the seronegative group, low titers of rubella antibodies, 10.5 post-vaccination, were predicted by high internalizing or neuroticism scores, and by low self-esteem, measured at baseline. Higher externalizing scores indirectly predicted lower titers of antibodies, via fatigue-related symptoms, measured 10 weeks post vaccination. In contrast, in the seropositive group no association was found between any of the psychological variables and antibody titers. Personality and other psychological variables can predict antibody titers to rubella vaccination, in infected individuals. The associations between the psychological variables and antibody titers are complex, and involve both direct and indirect associations. Specific psychological variables can also be used to predict levels of post-vaccination fatigue.