COVID Arm: Delayed Hypersensitivity Reactions to SARS-CoV-2 Vaccines Misdiagnosed as Cellulitis

Abstract

The term “COVID arm” has been coined to describe a harmless delayed hypersensitivity reaction occurring approximately a week after administration of the novel SARS-CoV-2 mRNA vaccine. It appears as a red, warm, pruritic, indurated, or swollen area in the vicinity of the vaccine site. These reactions, especially if accompanied by systemic symptoms, have been mistaken for cellulitis. We report 3 cases of COVID arm, 2 of which were mistaken for cellulitis. Distinguishing features of COVID arm from cellulitis include pruritus as a common finding, occurrence approximately a week after vaccination, a lack of progression of symptoms, rapid response to topical steroids, and/or spontaneous resolution usually over 4 to 5 days. Practice Points: • Patients receiving SARS-CoV-2 vaccines may experience delayed hypersensitivity reactions characterized by erythema, swelling, and itching occurring near the vaccination site (COVID arm), approximately a week after vaccination. • Clinicians can distinguish SARS-CoV-2 vaccine reactions from cellulitis by the time of onset (approximately a week vs 5 days), by the lack of progression of symptoms, and resolution over 4 to 5 days. • Severe cases of COVID arm may be treated with topical steroids.

Cutaneous Adverse Reactions Associated with SARS-CoV-2 Vaccines

“…Similar findings were confirmed in Black, Indigenous, or People of Color [10]. The so-called COVID arm is an erythematous, indurated, edematous, itchy, or painful plaque of different sizes developing in the area where the vaccine was inoculated [11,12]. Necrotic lesions characterized by angulated eschars surrounded by indurated erythematous borders at site of inoculation were reported one week after BNT162b2 vaccination [13].…”

“…The COVID arm can recur with the booster but is, on average, likely to be less severe and may develop faster [7]. In the case of fever, the suspect of cellulitis should be ruled out [12]. Histopathology shows a superficial and deep perivascular lymphocytic infiltrate with dilated vessels, intraluminal neutrophils, and negative immunohistochemistry for the SARS-CoV-2 spike protein, consistent with delayed-type or T-cell-mediated hypersensitivity reactions [12].…”

“…In the case of fever, the suspect of cellulitis should be ruled out [12]. Histopathology shows a superficial and deep perivascular lymphocytic infiltrate with dilated vessels, intraluminal neutrophils, and negative immunohistochemistry for the SARS-CoV-2 spike protein, consistent with delayed-type or T-cell-mediated hypersensitivity reactions [12]. Symptomatic therapies as antihistamines and/or topical glucocorticoids can be used for treatment, as for drug-induced injection site reactions [14,15].…”

The Impact of COVID-19 Pandemic on Dermatological Conditions: A Novel, Comprehensive Review

“…As discussed earlier, Moderna and Pfizer vaccines contain excipients such as polyethylene glycol, which is proposed to elicit DTHR [ 178 ]. In the United States, Pfizer vaccines have been administered in similar amounts to the Moderna vaccine [ 179 ].…”

A perspective on discussing COVID-19 vaccines: Efficacy and adverse effects

“…The authors describe a strikingly infl ammatory soft-tissue reaction in the vaccine-injected arm. Although seemingly distinctive, as with all uncommon reactions, it is diffi cult to be certain whether this reaction is fairly unique to mRNA COVID vaccines, or if it has been highlighted here and elsewhere 3 because of a hyperacute level of vigilance and heightened desire to share information about these vaccines with the medical community.…”