Predicting Vaccination Side Effects: How Psychological Factors Promote Symptom Reports Following Influenza Vaccination

Abstract

Medication side effects pose a significant challenge to modern healthcare. For vaccinations specifically, side effects have decreased the confidence that patients and clinicians have in the safety of the medication and have contributed to a rece1nt resurgence in the anti-vaccination movement. This movement has decreased vaccination uptake and contributed to rising incidence in vaccine preventable diseases. However, preliminary evidence suggests that a proportion of vaccination side effects may not be caused by active ingredients of the medication, but instead are associated with psychological factors and the nocebo effect. This study investigates if, and how, pre-vaccination psychological and demographic factors predict symptom reports post-vaccination. Similarly, the study investigated whether these symptoms then influence future intention to vaccinate. To conduct the investigation, the study employed a prospective, longitudinal design in which 225 influenza vaccination recipients were assessed at baseline and at two points after receiving the vaccination. Psychological and demographic variables were measured at baseline, while symptom experience and interpretation were measured immediately and one-week following the vaccination. Analyses revealed the presence of nocebo effects following influenza vaccination. Immediately following the vaccination, anxiety (p<.001) predicted the number and severity of symptoms that a participant reported. One-week following the vaccination, anxiety (p<.001) and baseline symptoms (p=.011) predicted the number of symptoms a participant reported. When these symptoms were experienced, gender (p=.004), optimism (p<.001), and total symptom experience (p<.001) predicted whether participants interpreted them as vaccination side effects. While no significant results were found for anti-vaccination attitudes, the variable approached significance (p=.083) in the regression model predicting vaccination symptom attribution. Interestingly, symptoms typically associated with influenza were also more likely to be interpreted as caused by the vaccination. Overall, these findings suggest that nocebo-associated, psychological factors contribute to the symptoms experienced after an influenza vaccination. Specifically, there appears to be two separate influences on how symptoms are noticed and then interpreted as side effects. This data may facilitate more accurate diagnosis of physical and psychological associated vaccine side effects. Furthermore, the study suggests that psychotherapeutic interventions may be an effective approach to addressing vaccination side effects and limiting the development of antivaccination attitudes and vaccination nonadherence.