Time for Resolution of COVID-19 Vaccine–Related Axillary Lymphadenopathy and Associated Factors

Abstract

Background. The variable clinical course of subclinical lymphadenopathy detected on breast imaging after COVID-19 vaccination creates management challenges and has led to evolving practice recommendations. Objective. To assess the duration of axillary lymphadenopathy ipsilateral to COVID-19 vaccination detected by breast imaging and to assess factors associated with the time until resolution. Methods. This retrospective single-center study included 111 patients (mean, 52±12 years) with unilateral axillary lymphadenopathy ipsilateral to Pfizer or Moderna COVID-19 vaccine administration performed within the prior 8 weeks that was detected on breast ultrasound performed between January 1st, 2021, and October 1st, 2021 and that underwent follow-up ultrasound examinations at 4-12 week intervals until resolution of the lymphadenopathy. Patient information was extracted from medical records. Cortical thickness of the largest axillary lymph node on ultrasound was retrospectively measured and was considered enlarged when greater than 3 mm. Multivariable linear regression analysis was used to identify independent predictors of the time until resolution. Results. The mean cortical thickness on the initial ultrasound was 4.7±1.2 mm. The lymphadenopathy resolved a mean of 97±44 days after the initial ultrasound and 127±43 days after the first vaccine dose, as well as after a mean of 2.4±0.6 follow-up ultrasound examinations. Significant independent predictor of shorter time to resolution was Pfizer (rather than Moderna) vaccination [coefficient=-18.0 (95% CI: -34.3, -1.7); p=.03], and significant independent predictors of longer time to resolution were receipt of the second dose after the initial ultrasound [coefficient=19.2 (95% CI: 3.1, 35.2); p=.02] and greater cortical thickness on the initial ultrasound [coefficient=8.0 (95% CI: 1.5, 14.5); p=.02]. Patient age, prior history of breast cancer, and axillary symptoms were not significantly associated with time to resolution (all p>.05). Conclusion. Axillary lymphadenopathy detected by breast ultrasound after COVID-19 mRNA vaccination lasts longer than reported in initial vaccine clinical trials. Clinical Impact. The prolonged time for resolution supports not delaying screening mammography due to recent COVID-19 vaccination as well as the recent professional society recommendation of a follow-up interval of at least 12 weeks for suspected vaccine-related lymphadenopathy.