Silvester, CGasteiger, CGamble, GDWilson, MSFaasse, KPetrie, KJMacKrill, K2026-05-202026-05-202025-03-26Annals of behavioral medicine : a publication of the Society of Behavioral Medicine, ISSN: 1532-4796 (Print); 1532-4796 (Online), Oxford University Press (OUP), 59(1), kaaf024-. doi: 10.1093/abm/kaaf0241532-47961532-4796http://hdl.handle.net/10292/21133BACKGROUND: Side effects following vaccination intensify vaccine hesitancy, which remains a significant challenge to public health. Research suggests that a proportion of side effects are not caused by the vaccine but are instead associated with psychological factors that influence nocebo responding. PURPOSE: This study investigates the psychological and demographic factors associated with symptom reporting postvaccination, the attribution of these symptoms as side effects, and their influence on future intentions to vaccinate. METHODS: A prospective, longitudinal design was employed with 225 influenza vaccination recipients. Demographic and psychological measures (including anxiety, vaccination attitudes, and side effect expectations) were completed at baseline. Side effects were measured immediately and 1-week following the vaccination. Future intentions to vaccinate were measured 1-week postvaccination. RESULTS: Anxiety (P < .001) and perceived sensitivity to vaccines (P = .044) predicted the number of symptoms reported immediately following vaccination. Anxiety (P < .001) and perceived sensitivity (P = .035) along with baseline symptoms (P < .001) predicted symptoms 1 week following the vaccination. Female gender (P = .003), younger age (P = .018), anxiety (P < .001), and baseline symptoms (P = .009) predicted whether participants attributed symptoms as vaccination side effects. Anti-vaccination attitudes were associated with less intention to vaccinate in the future (P = .033). CONCLUSIONS: Nocebo-associated psychological factors contributed to symptoms experienced after an influenza vaccination. Findings demonstrate that the way symptoms are noticed, and then interpreted as side effects, appear to be separate mechanisms promoted by different factors. This study improves identification of side effect reporters prior to vaccination.© The Author(s) 2025. Published by Oxford University Press on behalf of the Society of Behavioral Medicine. This is an open access article distributed under the terms of the Creative Commons CC BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. You are not required to obtain permission to reuse this article.anti-vaccinationinfluenzanoceboside effectsvaccination52 PsychologyPneumonia & InfluenzaPreventionImmunizationMental HealthInfectious DiseasesClinical ResearchVaccine RelatedBehavioral and Social ScienceEmerging Infectious DiseasesInfluenzaBiodefense3.4 Vaccines3 Good Health and Well Being11 Medical and Health Sciences13 Education17 Psychology and Cognitive SciencesPublic Health42 Health sciences52 PsychologyHumansFemaleMaleInfluenza VaccinesAdultMiddle AgedAnxietyVaccinationProspective StudiesLongitudinal StudiesInfluenza, HumanYoung AdultIntentionAgedHealth Knowledge, Attitudes, PracticeAdolescentVaccination HesitancyHumansInfluenza VaccinesVaccinationLongitudinal StudiesProspective StudiesHealth Knowledge, Attitudes, PracticeAnxietyIntentionAdolescentAdultAgedMiddle AgedFemaleMaleInfluenza, HumanYoung AdultVaccination HesitancyHumansFemaleMaleInfluenza VaccinesAdultMiddle AgedAnxietyVaccinationProspective StudiesLongitudinal StudiesInfluenza, HumanYoung AdultIntentionAgedHealth Knowledge, Attitudes, PracticeAdolescentVaccination HesitancyJournal ArticleOpenAccess10.1093/abm/kaaf024