First Report of Secondary and Tertiary Transmission of Vaccinia Virus Occurrence After Sexual Contact with a Smallpox Vaccinee

In 2002, the U.S. Department of Defense resumed smallpox vaccination for designated military personnel, civilian employees, and contractors. The smallpox vaccine licensed for use in the United States contains live vaccinia virus. The CDC Laboratory Response Network supports a nonvariola Orthopoxvirus test that can identify vaccinia and other nonvariola orthopoxviruses in clinical specimens. Since the Department of Defense resumed smallpox vaccination, cases of secondary transmission of vaccinia virus from military smallpox vaccinees have been reported among intimate, sports-related, and household contacts. Tertiary transmission has been reported among household and sports contacts and from mother to child through breastfeeding. The following case report is the first reported instance of tertiary vaccinia transmission through sexual contact.


On June 24, 2012, the CDC notified the Public Health Services, of the County of San Diego Health and Human Services Agency, of a suspected case of vaccinia virus infection transmitted by sexual contact. The case had been reported to the CDC by an infectious disease specialist who had requested vaccinia immune globulin intravenous (VIGIV) for a patient with lesions suspicious for vaccinia.


VIGIV is the only licensed treatment available for complications from vaccinia virus infection. Indications for its use include treatment or mitigation of aberrant vaccinia infections that pose a particular hazard (e.g., inadvertent inoculation of the eyes or mouth) as well as eczema vaccinatum, progressive or severe generalized vaccinia infections, and other skin conditions. The majority of adverse vaccinia reactions do not require treatment beyond supportive care. VIGIV is reserved for patients with serious clinical disease or for those at risk for experiencing severe disease. CDC is the sole source of VIGIV for civilians.


The patient reported two recent sexual contacts: one with a partner who recently had been vaccinated against smallpox and a later encounter with an unvaccinated partner. Infections resulting from secondary transmission of vaccinia virus from the smallpox vaccinee to the patient and subsequent tertiary transmission of the virus from the patient to the unvaccinated partner were confirmed by the County of San Diego Public Health Laboratory. The smallpox vaccine had been administered under the U.S. Department of Defense smallpox vaccination program. The vaccinee did not experience vaccine-associated complications. However, the secondary and tertiary patients were hospitalized and treated with VIGIV. No further transmission was known to have occurred.


The vaccinee was identified as a civilian who had received his first smallpox vaccine in June 2012 under the Department of Defense smallpox vaccination program. At a routine follow-up examination to check the inoculation site on June 13, the vaccinee reported not having kept the site covered as instructed. Clinic staff members again instructed him to keep the lesion covered and repeated the instructions provided previously to reduce the risk for vaccinia transmission to others. The vaccinee experienced the expected pustular lesion at the inoculation site on his left upper arm and did not experience any secondary lesions or complications. The vaccinee was interviewed on July 9, during epidemiologic investigation of the secondary and tertiary patients. He confirmed that no secondary lesions had occurred and reported that the secondary patient was his only sexual contact during the infectious window, days 2 to 30 after receiving the smallpox vaccine.


Interviewed at the time of illness, neither patient reported having additional sexual contacts or living with persons who might be at risk for complications from vaccinia infection. Persons at risk include those who are immunosuppressed, pregnant women, or persons with a history of atopic dermatitis. The patient with tertiary infection did not go to work on the day he experienced symptoms and returned when his lesions were healed adequately. Both patients wore contact lenses, which can pose a hazard for ocular autoinoculation with the virus. Neither patient wore eyeglasses in lieu of contact lenses. Extensive patient instructions were provided to prevent autoinoculation and further transmission to contacts. Recommendations focused on refraining from sexual or other intimate contact until lesions had healed completely, the importance of hand hygiene (especially when handling contact lenses), managing infectious fomites (e.g., clothing, bedding, and towels), and lesion care. The military clinic that administered the smallpox vaccine was contacted to ensure vaccinees were provided the required instructions regarding preventing virus transmission to others. No further transmission of vaccinia virus by the smallpox vaccinee or the secondary or tertiary patient has been reported.


The secondary and tertiary patients in this investigation experienced symptoms of systemic illness, localized proliferation of vaccinia lesions, and singular lesions at locations remote from the principal inoculation sites. Lesions in the genital and perianal areas are challenging for preventing autoinoculation and further local inoculation by clothing and other fomites. A possible history of atopic dermatitis was concerning. However, the major reason why the decision was made to administer VIGIV to both patients was because of lesion location, number, and progression.


Both patients sought medical care early in the course of disease, which also contributed to the decision to administer VIGIV. Early presentation provided an opportunity to supply antivaccinia antibodies when the patients' immune systems were beginning to respond to the infection. These case reports describe secondary and tertiary transmission of vaccinia virus through sexual contact, highlighting the potential for vaccinia infections to spread beyond immediate intimate contacts of smallpox vaccinees. The illness experienced by the two patients and the potential for further contact transmission underscores the importance of smallpox vaccinee compliance with covering the inoculation site and instruction regarding the particular hazards of vaccinia transmission to genital and perianal areas.


See the CDC Report


See the FDA’s VIGIV Information


See also Medical Law Perspectives, January 2013 Report: Vaccines: An Ounce of Prevention May Lead to a Pound of Injury.