Monkeypox infection in a patient vaccinated against smallpox

In a recent study published in the Emerging infectious diseases

Research letter: Monkeypox in a patient vaccinated with the ACAM2000 smallpox vaccine during the 2022 outbreak. Image credit: Dotted Yeti/Shutterstock

Patient characteristics

In the present study, the team reported the case of a patient residing in Washington, United States, who had been infected with the monkeypox virus. However, he had been successfully vaccinated against smallpox with the ACAM2000 smallpox vaccine eight years previously.

The patient was a 34-year-old man who reported having sex with men. He presented to a clinic specializing in sexually transmitted infections with a history of malaise, fatigue and headaches for four days, as well as four painless penile lesions for two days. The patient was assessed at a local emergency department two days prior to his clinic visit. He tested negative for Chlamydia trachomatis, Neisseria gonorrhea and herpes simplex virus. While his constitutional symptoms improved over the next two days, his penile ulcers turned into white papular lesions.

The patient reported a history of syphilis and N. gonorrhea in 2017 which resolved after treatment. His military medical records did not show a history of human immunodeficiency virus (HIV) infection or other immunocompromising conditions. She had previously been recommended daily treatment with emtricitabine/tenovir as a pre-exposure prophylactic measure for HIV. However, he stopped this treatment a year before seeing a doctor. In the past 90 days, the patient reported having had penetrative oral receptive and anal sex with 13-14 new partners without using a condom. His last reported sexual encounter was 11 days before he was due to see a doctor, when he had unprotected penetrative anal sex with only one partner at a local Pride event.

Due to his military service, the patient was vaccinated against smallpox with the ACAM2000 vaccine in March 2014. Furthermore, he denied any recent travel outside of Washington or any contact with sick people.


The results of the study showed that the patient had four ulcerated penile lesions that had progressed to a patch on the foreskin. This plaque was observed two days after the patient developed constitutional symptoms. The lesions were not tender and no discharge was observed. A tender right inguinal lymph node was also seen, along with a vaccination scar on his right deltoid.

The team noted that the patient tested positive for non-variola orthopoxvirus by polymerase chain reaction (PCR). Subsequent testing showed that the clade II strain was the source of the infection. However, the patient tested negative for hepatitis C, syphilis, and HIV-1/2 antigen and antibody.

The patient required only supportive care with the administration of oral acetaminophen to treat constitutional symptoms, which resolved ten days after symptom onset. The rash progressed, coalesced and formed into a pustule six days after the onset of constitutional symptoms. The lesion evolved into an ulcer on day 16 before dissipating without leaving residual scars.

Overall, the study showed that while vaccination is essential to prevent infectious disorders, vaccination alone may be insufficient to confer immunity against monkeypox infection. Therefore, the researchers believe that vaccination should complement, not replace, public health campaigns that facilitate the reduction of high-risk health behaviors.

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