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Introduction: Following vaccination of Israeli population with Pfizer-BioNTech COVID-19 Vaccine, an unusual increase in axillary-lymphadenopathy was noted. This study assesses the rate and magnitude of this trend from breast-imaging standpoint. Materials and Methods: Participants undergoing breast-imaging, in whom isolated axillary-lymphadenopathy was detected were questioned regarding SARS-CoV-2 vaccine to the ipsilateral arm. Patients’ and imaging characteristics were statistically compared. In order to perform a very short-term follow-up, twelve healthy vaccinated medical staff-members, underwent axillary-ultrasound shortly after the second dose, and follow-up. Results: Axillary-lymphadenopathy attributed to vaccination was found in 163 women undergoing breast-imaging, including BRCA -carriers. During the study, number of detected lymphadenopathies increased by 394% (p=0.00001) in comparison with previous two consecutive years. Mean cortical-thickness of abnormal lymph-nodes after second dose vaccination was 5±2 mm. Longer lymph-node diameter after second vaccination was noted (from 15±5 mm, to 18±6 mm, p=0.005). In the subgroup of medical staff members, following trends were observed: in patients with positive antibodies, lymph-node cortical-thickness was larger than patients with negative serology (p=0.03); lymph-node cortical-thickness decreased in 4-5 weeks follow-up (p=0.007). Lymphadenopathy was evident on mammography in only 49% of cases. Discussion: Vaccine-associated lymphadenopathy is an important phenomenon with great impact on breast-imaging clinic workload. Results suggest the appearance of cortical thickening shortly after both doses. Positive serology is associated with increased lymph-node cortical-thickness. In asymptomatic vaccinated women with ipsilateral axillary-lymphadenopathy as the only abnormal finding, radiological follow-up is probably not indicated. BRCA -carriers, although at higher risk for breast-cancer, should probably receive the same management as average-risk patients.

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