PT - JOURNAL ARTICLE AU - Mohamed S El-Sayed AU - Godfrey N Wechie AU - Chen Sheng Low AU - Oludolapo Adesanya AU - Nikhil Rao AU - Vincent J Leung TI - The incidence and duration of COVID-19 vaccine-related reactive lymphadenopathy on <sup>18</sup>F-FDG PET-CT AID - 10.7861/clinmed.2021-0420 DP - 2021 Nov 01 TA - Clinical Medicine PG - e633--e638 VI - 21 IP - 6 4099 - http://www.rcpjournals.org/content/21/6/e633.short 4100 - http://www.rcpjournals.org/content/21/6/e633.full SO - Clin Med2021 Nov 01; 21 AB - Objectives Reactive axillary lymph nodes (ALN) may occur post-COVID-19 vaccination. This may be confused with malignant nodal metastases on oncological imaging. We aimed to determine the reactive ALN incidence and duration on 18F-fluorodeoxyglucose positron emission tomography – computed tomography (18F-FDG PET-CT), and its relationship with gender, age and vaccine type.Methods A retrospective study was performed. Two-hundred and four eligible patients had 18F-FDG PET-CT between 01 January 2021 and 31 March 2021, post-vaccination with Pfizer-BioNTech or Oxford-AstraZeneca vaccine. Image analysis was performed on dedicated workstations. SPSS was used for statistical analysis.Results Thirty-six per cent of patients had reactive ALN until 10 weeks post-vaccination; reducing in frequency and intensity with time. Women were more likely to have reactive ALN compared with men. The frequency and intensity were higher in patients aged &lt;65 years compared with those aged ≥65 years. However, no difference was found between both vaccine types in our study cohort.Conclusions Physicians’ awareness of COVID-19 vaccine-related reactive ALN on 18F-FDG PET-CT is important to avoid inappropriate upstaging of cancers.