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

Abstract

BackgroundBoth temporal changes in imaging characteristics of lymphadenopathy on US following COVID-19 vaccination and expected duration of radiologically evident lymphadenopathy remain uncertain.PurposeTo longitudinally evaluate COVID-19 vaccine-associated lymphadenopathy on axillary US at various time intervals, in both mRNA and vector vaccine recipients.Materials and MethodsThis 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 manifesting lymphadenopathy. Following variables were assessed: cortical thickness, number of lymph nodes, morphology, and Doppler signal. Temporal changes in cortical thickness and number of lymph nodes during follow-up were assessed using a linear mixed model.ResultsNinety-one women with lymphadenopathy in the vaccinated arm had undergone a total of 215 serial US (mean age, 44 years ±13). Fifty-one participants had received vector vaccine (ChAdOx1 nCoV-19 vaccine) and 40 mRNA vaccines (BNT162b2 vaccine [n=37] and mRNA-1273 vaccine [n=3]). Except for three women with follow-up loss, eighty-eight women underwent serial US and complete resolution of axillary lymphadenopathy at median 6 weeks interval (range, 4-7 weeks) was observed in 26% (23 of 88) of women. Of 49 women with follow-up US at median 12 weeks interval (range, 8-14 weeks), persistent lymphadenopathy was observed in 51% (25 of 49). During the follow-up period, the cortical thickness gradually decreased (P < .001) over time 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 over 6 weeks on US. 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 mRNA vaccine.© RSNA, 2022See also the editorial by Moy and Kim.