Dermatology MCQ - Viral Infections - Vaccinia

A research scientist working with a recombinant vaccinia virus accidentally punctures their glove and skin with a contaminated needle. Several days later, a painful, well-circumscribed ulcer with a central black eschar and a surrounding erythematous halo develops at the inoculation site. Which of the following is the most appropriate next step in management?

A) Immediate administration of intravenous acyclovir
B) Surgical debridement of the eschar
C) Administration of vaccinia immune globulin (VIG)
D) Application of topical trifluridine
E) Initiation of oral valganciclovir

Correct Answer: C) Administration of vaccinia immune globulin (VIG)

Explanation

This scenario describes a classic accidental autoinoculation with vaccinia virus, which can occur in laboratory workers or recently vaccinated individuals.

Key Clinical Features of Vaccinia Inoculation:

• The lesion described—a painful ulcer with a central black eschar (necrosis) and a surrounding red halo—is a hallmark of a developing vaccinia lesion, often called a "take" or a primary vaccination reaction.

• The progression is typically: papule → vesicle → pustule → umbilication → ulceration with eschar → healing with scar.

Management of Complications:

For a healthy individual, autoinoculation (e.g., to the eye, genitals, or face) is often self-limited. However, in certain high-risk scenarios or with severe progressive disease, specific treatment is indicated:

• Vaccinia Immune Globulin (VIG): This is the first-line treatment for severe vaccinia virus infections, including:

  • Progressive vaccinia (vaccinia necrosum): A rare, severe complication seen in immunocompromised individuals where the infection progresses beyond the inoculation site without healing.

  • Eczema vaccinatum: A disseminated spread in individuals with a history of atopic dermatitis.

  • Severe generalized vaccinia.

  • Vaccinia infections in immunocompromised patients.

• VIG provides neutralizing antibodies to help control the viral replication.

Why Not the Other Options?

• (A) Intravenous acyclovir & (E) Oral valganciclovir: Vaccinia is a double-stranded DNA poxvirus. It is not sensitive to antiviral drugs that target viral DNA polymerase with high specificity, like acyclovir or ganciclovir (which are effective against herpesviruses). Tecovirimat is the antiviral of choice for orthopoxviruses, not listed here.

• (B) Surgical debridement: This is contraindicated in the early stages as it can promote viral dissemination. The eschar will slough off on its own as the lesion heals.

• (D) Topical trifluridine: This is a topical antiviral used for herpes simplex keratitis. It is not indicated for cutaneous vaccinia infection.

Prevention:
This accident underscores the importance of proper personal protective equipment (PPE) and pre-vaccination for at-risk laboratory workers handling replication-competent vaccinia virus.