The "Covid arm" is commonly seen in countries with high vaccination rates of Moderna's RNA vaccine and describes a local reaction with rashes at the injection site, although other localized rashes may occur on the elbow, hands and fingers.

Keywords: Covid; Covid arm; Local reaction; Moderna's RNA vaccine; Vaccination

Clinical Image
A 57-year-old female patient was administered 1 dose of Covid-19 Vaccine Moderna®. Apart from muscle pain and mild subfebrile temperatures in the first 24 hours, no side effects occurred. 8 days later, the patient noticed increasing redness at the injection site.
Clinical examination revealed a circular erythematous indurated plaque, mildly hyperthermic with tenderness on palpation in the area of the injection site on the left upper arm. Another erythematous papule was seen on the elbow of the same side (Figure 1). The patient was otherwise afebrile, in good general condition with no other complaints.
The plaques healed completely within 1 week after application of topical steroids (betamethasone cream). 2 days after the 2nd vaccination dose, the patient again noticed a barely visible circular redness, but it was much less pronounced than with the 1st dose.
Delayed local vaccination reactions, are observed after vaccination with Moderna® RNA vaccine, and are described as "Covid arm" [1]. In the "Covid arm", not only localized rashes at the injection site are described. As in this case, there are other reports of additional localized cutaneous rashes on the elbows, palms, and fingers. They can typically occur 4-11 days after 1st vaccination and 1-3 days after 2nd vaccination. The pathomechanism is thought to be a delayed T-cell-mediated hypersensitivity reaction [2].
The "covid arm" is frequently observed in countries with high vaccination rates from Moderna's RNA vaccine. Clinicians should be familiar with this local reaction and be able to educate patients about the innocuous finding.