Axillary lymphadenopathy post-vaccination

In the American Journal of Roentgenology, researchers from the University of Pennsylvania offer their strategy for managing unilateral axillary lymphadenopathy detected on breast MRI in the weeks after COVID-19 vaccination. They note that in the Moderna clinical trial, 10% of vaccine recipients developed axillary swelling or tenderness ipsilateral to the vaccination arm within 7 days of the first dose, and 14% within 7 days of the second dose. Rates in the Pfizer-BioNTech trial were lower but likely an underestimate, they note. They say that such a finding is most likely to be related to the COVID-19 vaccine if it occurs within 4 weeks after either dose. In these situations, they consider the lymphadenopathy to be BI-RADS 3 (probably benign) and advise performing follow-up ultrasound within 6 to 8 weeks after the second vaccine dose.

American Journal of Roentgenology article on axillary lymphadenopathy