Acute onset supraclavicular lymphadenopathy coinciding with intramuscular mRNA vaccination against COVID-19 may be related to vaccine injection technique, Spain, January and February 2021

Euro Surveill. 2021 Mar;26(10):2100193. doi: 10.2807/1560-7917.ES.2021.26.10.2100193.


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.

Keywords: COVID-19; Vaccine; adverse events; mRNA vaccine; supraclavicular lymphadenopathy.

MeSH terms

  • COVID-19 / prevention & control*
  • COVID-19 Vaccines / adverse effects*
  • Humans
  • Injections, Intramuscular / adverse effects
  • Lymphadenopathy* / diagnosis
  • Lymphadenopathy* / etiology
  • RNA, Messenger / administration & dosage
  • Spain
  • Vaccination / adverse effects*


  • COVID-19 Vaccines
  • RNA, Messenger