COVID-19 has been associated with several skin manifestations, ranging from urticarial rash, morbilliform exanthema, papulovesicular exanthema to livedo reticularis and purpuric exanthema. Recently, Maia and colleagues [2] reported an increased number of varicella–zoster virus cases in Brazil and assumed an association with the COVID-19 pandemic.

Varicella–zoster virus belongs to the Herpesviridae family, and it is the causative agent of chickenpox in children and young adults, and shingles, mainly in adults. After the resolution of the primary infection, the virus remains latent in the ganglia of the dorsal roots of the cranial nerve. Stress or trauma, other than immunosuppression status, can reactivate the virus causing Herpes Zoster disease, also known as shingles.

The papulovesicular rash described in our report strongly recalls a varicella–zoster virus reactivation triggered by the second dose of the Pfizer-BioNTech vaccine. Consistent with the Varicella–zoster incubation period, which ranges from 1 to 5 days, the subject started to develop the rash 3 days after the vaccine injection. Also, the evolution of the rash is typical, starting with an urticarial-like papular rash, and becoming vesicular with blisters filled with serous exudates immediately after. Moreover, the lesions developed in the innervation territory of the roots of the left brachial plexus (from C5 to T1 dermatomes) that is in line with the typical shingles presentation, which follows a dermatomal distribution.

Although the absence of laboratory tests (varicella–zoster virus-specific IgM antibodies and/or PCR) and histological evaluation, which would confirm the diagnosis, the hypothesis of a varicella–zoster virus reactivation is conceivable. This is further supported by the varicella infection during the subject’s childhood.

It is interesting to note that cases of varicella–zoster virus reactivation have already been described following vaccinations against Hepatitis A, influenza virus, rabies and Japanese encephalitis [3]. Recently, two cases of Herpes Zoster reactivation have been associated with COVID-19 vaccination; the first, a 78-year-old man with a history of hypertension, cerebrovascular accident and bladder cancer, after the inoculation of an inactivated COVID-19 vaccine [4]; the second, a 79-year-old man with a history of hypertension and anti-neutrophilic cytoplasmic antibody-related glomerulonephritis, after mRNA COVID-19 vaccination [5]. Moreover, Furer and colleagues recently described an interesting case series of varicella–zoster virus reactivation in 6 patients affected by autoimmune inflammatory rheumatic disease after Pfizer-BioNTech inoculation [6]. Thus, the present report constitutes the first case documented on a rare case of varicella–zoster virus reactivation on a healthy, young adult male without pre-existing conditions.

The Pfizer-BioNTech vaccine is the first approved vaccination by the FDA and administered in the USA and globally. The most common adverse effects are mild to moderate, and they can be local, involving the site of the injection (pain, swelling and redness) or systemic (chills, tiredness, and headache). In addition, diarrhea, nausea, vomiting, and deep tiredness have also been described.

We still know little about rare and long-term side effects related to COVID-19 vaccines and, even though the vaccination is crucial to stop spreading the virus, it is also important to monitor and report any possible adverse effect associated with the administration of the vaccines. Despite the impossibility of establishing the causal relation between our patient rash and the vaccine, it is reasonable to hypothesize that the vaccination-induced immune stress triggered the varicella–zoster virus reactivation, which is also consistent with the clusters of varicella–zoster virus reactivation already described in COVID-19 patients or in immune-compromised individuals.

The incidence of shingles after the COVID-19 vaccine inoculation is not known, more studies are needed to understand how the reactivation of varicella–zoster virus and the Pfizer-BioNTech vaccine are related.