RT Journal Article T1 Acute onset supraclavicular lymphadenopathy coinciding with intramuscular mRNA vaccination against COVID-19 may be related to vaccine injection technique, Spain, January and February 2021 A1 Fernández Prada, María A1 Rivero Calle, Irene A1 Calvache González, Ana A1 Martinón Torres, Federico AB Monitoring adverse reactions following immunisation is essential, particularly for new vaccines such as those against COVID-19. We describe 20 cases of acute onset of a single supraclavicular lymphadenopathy manifesting between 24 h and 9 days after ipsilateral intramuscular administration of an mRNA-based COVID-19 vaccine, referred to our WHO Collaborating Centre for Vaccine Safety. Our results indicate that the swelling of supraclavicular lymph nodes following immunisation may constitute a benign and self-limited condition, related to a higher than recommended injection site PB European Centre for Disease Prevention and Control (ECDC) SN 1560-7917 YR 2021 FD 2021 LK http://hdl.handle.net/10347/26768 UL http://hdl.handle.net/10347/26768 LA eng NO Euro Surveill. 2021; 26(10): pii=2100193. https://doi.org/10.2807/1560-7917.ES.2021.26.10.2100193 DS Minerva RD 28 abr 2026