US Evaluation of Axillary Lymphadenopathy Following COVID-19 Vaccination: A Prospective Longitudinal Study

Background: Both temporal changes in imaging characteristics of lymphadenopathy on US scans after COVID-19 vaccination and expected duration of radiologically evident lymphadenopathy remain uncertain. Purpose: To longitudinally evaluate COVID-19 vaccine-associated lymphadenopathy on axillary US scans at various time intervals in both messenger (mRNA) and vector vaccine recipients. Materials and Methods: This prospective cohort study was conducted between March 2021 and January 2022. The participants were asymptomatic women without breast cancer who had received COVID-19 vaccination. Serial follow-up US was performed in women with lymphadenopathy. The following variables were assessed: cortical thickness, number of lymph nodes, morphologic characteristics, and Doppler signal. Temporal changes in cortical thickness and number of lymph nodes during follow-up were assessed using a linear mixed model. Results: Ninety-one women with lymphadenopathy in the vaccinated arm had undergone a total of 215 serial US examinations (mean age, 44 years +/- 13 [SD]). Fifty-one participants had received a vector vaccine (ChAdOx1 nCoV-19 vaccine) and 40 had received an mRNA vaccine (BNT162b2 vaccine [n = 37) and mRNA-1273 vaccine [n = 3]). Three of the 91 women were lost to follow-up: thus, 88 women underwent serial US. Complete resolution of axillary lymphadenopathy was observed at a median of 6 weeks after vaccination (range, 4-7 weeks) in 26% of women (23 of 88). Among 49 women with follow-up US at a median of 12 weeks diet vaccination (range, 8-14 weeks), persistent lymphadenopathy was observed in 25 (51%). During the follow-up the cortical thickness gradually decreased (P < .001) over rime regardless of vaccine type; however, values were higher in recipients of the mRNA vaccine than in recipients of the vector vaccine (P = .02). Conclusion: COVID-19 vaccine-associated axillary lymphadenopathy frequently persisted for more than 6 weeks on US scans. Lymphadenopathy should be interpreted considering vaccine type and time elapsed since vaccination. Follow-up US examination at least 12 weeks after vaccination may be reasonable, particularly for recipients of the messenger RNA vaccine. (C) RSNA, 2022

Automated summary

This study longitudinally evaluated changes in axillary lymphadenopathy after COVID-19 vaccination using serial ultrasound scans. The research found that lymphadenopathy usually resolves completely within 6 weeks after vaccination, but some patients may continue to have lymphadenopathy. Recipients of mRNA vaccines had higher cortical thickness, indicating a longer duration of lymphadenopathy. Follow-up ultrasound examination at least 12 weeks after vaccination may be necessary, especially for mRNA vaccine recipients.