It is important to evaluate the vaccine-related metabolic changes on FDG PET/CT to avoid confusing results. The investigators aimed to assess the frequency and intensity of regional and systemic metabolic PET/CT changes of patients who received the mRNA-based COVID-19 vaccine (BNT162b2-Pfizer/BioNTech) and to analyze possible factors affecting these changes.

Inclusion Criteria:

• patients referred for post-vaccination FDG PET/CT imaging

Exclusion Criteria:

• Disseminated metastatic disease, ipsilateral breast cancer or lymphoma that was likely to involve axilla, and patients who had ipsilateral intense axillary uptake or thyroiditis on their prior imaging, were exclusion criteria

recently vaccinated patients who underwent FDG PET/CT imaging between July 2021 and December 2021, were included in this prospective analysis

study results