COVID Arm: Delayed Local Reaction to Vaccine

A 33-year-old presents to her dermatologist with new onset of an itchy, red rash on the left arm, which started six days after receiving the COVID-19 vaccine in the affected area. 

On examination, they have a well-circumscribed, erythematous, edematous plaque on the left upper lateral arm. This clinical entity is a delayed local reaction to the mRNA-1273 SARS-CoV2 vaccine, which has been nicknamed as “COVID arm.” 

In recent reports, the onset of rash is delayed and ranges five to 11 days after vaccination. Appearance is variable; many are erythematous, indurated, and edematous while others are more targetoid or papular. The rash is often pruritic, sometimes painful, and can be associated with systemic symptoms such as fever, fatigue, and headache. 

As this is a relatively newer observation as large-scale vaccinations are being administered, it has been mistaken for skin infection and unnecessarily treated with antibiotics. Therefore, it is important for clinicians to have a high index of suspicion in recognizing this finding and reassure patients that they may complete their vaccination.

How can you distinguish delayed local reactions to a vaccine from cellulitis?

Further Reading

  1. Delayed large local reaction mRNA-1273 Vaccine against SARS-CoV-2
  2. “COVID Arm”: Very delayed large injection site reactions to mRNA COVID-19 vaccines


  1. Blumenthal KG, Freeman EE, Saff RR, Robinson LB, Wolfson AR, Foreman RK, Hashimoto D, Banerji A, Li L, Anvari S, Shenoy ES. Delayed Large Local Reactions to mRNA-1273 Vaccine against SARS-CoV-2. N Engl J Med. 2021 Apr 1;384(13):1273-1277. doi: 10.1056/NEJMc2102131. Epub 2021 Mar 3. PMID: 33657292; PMCID: PMC7944952.
  2. Ramos CL, Kelso JM. “COVID Arm”: very delayed large injection site reactions to mRNA COVID-19 vaccines. J Allergy Clin Immunol Pract. 2021 Apr 14:S2213-2198(21)00443-8. doi: 10.1016/j.jaip.2021.03.055. Epub ahead of print. PMID: 33864927.

Want more clinical cases?

Join Figure 1 for free and start securely collaborating with other verified healthcare professionals on more than 100,000 real-world medical cases just like this one.