Monkeypox vaccine: Special considerations for dermatologic patients

In 1980, the worldwide eradication of smallpox was declared, making its vaccination unnecessary and consequently producing a decrease in herd immunity against the virus.1 However, there is still a risk of a potential reintroduction of the disease either accidentally or intentionally. Likewise, there is the possibility of other orthopoxviruses (OPXV) emergence, as occurred in 2022 with Monkeypox virus (MPX), the etiological agent of monkeypox.2, 3 OPXV has a stable genome with a highly conserved protein structure, so although there are no vaccines specifically designed against MPX, smallpox vaccines may provide cross-immunity with an efficacy of more than 80%.3-6 These vaccines contain different strains of another OPXV called Vaccinia virus. The most commonly used strains in first- and second-generation vaccines have been Lister, Bern and Paris in Europe, New York City Board of Health (NYCBH) in North America, Tian Tan (VTT) in China, and Dairen and Ikeda in Japan.4 The original or first-generation vaccines are not currently available, but there are second- and third-generation vaccines with a better safety profile. However, their efficacy has not been demonstrated in real conditions.7 Second-generation vaccines, just like the original vaccines, contain live Vaccinia virus with replication capacity.8 They are administered in a single dose by multiple intradermal punctures, where the contact between the virus and the immune system takes place. It produces a papule that evolves into a vesicle or pustule, finally forming a scab which leaves a small scar.8 In addition to immunosuppression and the other usual contraindications for any live virus vaccine, the following dermatoses also contraindicate vaccination: a history of atopic dermatitis (AD) regardless of its degree of activity or severity, severe acne, Darier disease, psoriasis, impetigo, herpetic infection, extensive diaper dermatitis and burns.8 Cohabitants of persons with such pathologies should also avoid vaccination due to the risk of contagion through the lesion produced at the inoculation site.8 Moreover, although most of the adverse reactions to these vaccines are mild or self-limited, sometimes more serious reactions can occur, such as myocarditis or pericarditis.9 Skin reactions may be caused directly by the Vaccinia virus (eczema vaccinatum, generalized vaccinia or vaccinia gangrenosum) or immuno-mediated (erythema multiforme minor, Stevens–Johnson syndrome).9 Cases of encephalitis, encephalomyelitis and foetal Vaccinia infection have also been occasionally reported.9 An attenuated replication-defective Vaccinia virus strain called Modified Vaccinia Ankara (MVA) was developed through multiple serial passages in Germany. It was used during 1969–1988 as a first vaccine against smallpox in vulnerable population before the administration of the live virus vaccine to attenuate or avoid the side effects of the latter. Despite smallpox eradication, this MVA strain continued being modified, developing MVA-Bavarian Nordic (MVA-BN), a highly attenuated MVA unable to replicate in mammals.4, 10 This third-generation vaccine is even safer than its predecessor. Several studies have shown it is suitable for immunosuppressed persons including HIV patients and people with AD or other dermatoses.4, 7, 10 It was registered by the European Medicines Agency as Imvanex® and it is also known as JYNNEOS® in USA and Imvamune® in Canada. It is administered subcutaneously and two doses are required.7 Its efficacy has been compared with second-generation vaccines through two surrogate variables (the geometric mean of the antibody titre and the decrease in lesion size induced by the subsequent administration of the second-generation vaccine), obtaining a comparable efficacy with a better safety profile.7 It could also protect against the disease after infection, as shown in animal models trials with a virus similar to Variola virus.7 Given the dimensions of the current monkeypox outbreak (with more than 20,000 cases and 4 deaths in Europe to date), an increase in morbidity and mortality is expected as a consequence of the rise in the number of monkeypox patients with some type of immunosuppression, such as HIV.3 At this stage, although mass vaccination does not seem necessary for the time being according to World Health Organization, the MVA vaccine could still mark a milestone in the history of Public Health, as the original vaccine designed by Edward Jenner did.3, 4 None. None. The data that support the findings of this study are available from the corresponding author upon reasonable request.

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