povidone-iodine and Vaccinia

The U.S. Department of Defense vaccinates personnel deployed to high-risk areas with the vaccinia virus (VACV)-based smallpox vaccine. Autoinoculations and secondary and tertiary transmissions due to VACV shedding from the vaccination site continue to occur despite education of vaccinees on the risks of such infections. The objectives of this study were to investigate, in naïve smallpox vaccinees, (a) whether the vaccination site can remain contagious after the scab separates and (b) whether the application of povidone iodine ointment (PIO) to the vaccination site inactivates VACV without affecting the immune response. These objectives were tested in 60 individuals scheduled to receive smallpox vaccine. Thirty individuals (control) did not receive PIO; 30 subjects (treatment) received PIO starting on post-vaccination day 7. Counter to current dogma, this study showed that VACV continues to shed from the vaccination site after the scab separates. Overall viral shedding levels in the PIO group were significantly lower than those in the control group (p=0.0045), and PIO significantly reduced the duration of viral shedding (median duration 14.5 days and 21 days in the PIO and control groups, respectively; p=0.0444). At least 10% of control subjects continued to shed VACV at day 28, and 3.4% continued to shed the virus at day 42. PIO reduced the proportion of subjects shedding virus from the vaccination site from day 8 until days 21-23 compared with control subjects. Groups did not differ significantly in the proportion of subjects mounting an immune response, as measured by neutralizing antibodies, IgM, IgG, and interferon-gamma enzyme-linked immunospot assay. When applied to the vaccination site starting on day 7, PIO reduced viral shedding without altering the immune response. The use of PIO in addition to a semipermeable dressing may reduce the rates of autoinoculation and contact transmission originating from the vaccination site in smallpox-vaccinated individuals.

Topics: Adult; Anti-Infective Agents, Local; Antibodies, Neutralizing; Antibodies, Viral; Enzyme-Linked Immunospot Assay; Female; Humans; Immunity, Cellular; Interferon-gamma; Male; Military Personnel; Povidone-Iodine; Skin; Smallpox; Smallpox Vaccine; United States; Vaccination; Vaccinia; Vaccinia virus; Virus Shedding; Young Adult

One concern with traditional smallpox vaccination is inadvertent spread of virus to atopic or immunocompromised contacts. To reduce this risk, we tested the ability of povidone iodine to inactivate infectious virus at the vaccination site beginning at 7 days after transcutaneous smallpox vaccination. This ointment rapidly inactivated virus on the skin without reducing neutralizing antibody titers or antiviral T cell responses. Moreover, there was no delay in healing/eschar separation following povidone iodine application. Together, this indicates that administration of an antiviral/antimicrobial cream can effectively block virus shedding after traditional smallpox vaccination and reduce the risks of autoinoculation or contact spread.

Topics: Administration, Cutaneous; Adult; Female; Humans; Male; Middle Aged; Ointments; Povidone-Iodine; Risk Factors; Skin; Smallpox; Smallpox Vaccine; Treatment Outcome; Vaccination; Vaccinia; Vaccinia virus; Virus Shedding