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How can vaccinia virus spread from a smallpox vaccination site?
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smallpox
Edward Jenner vaccinating his child against smallpox; colored engraving.
The vaccinia virus, which is used in the smallpox vaccine, can spread from the site of vaccination through direct contact. This occurs if an individual touches the vaccination site and subsequently touches another area of their own body or another person.1
Because the vaccine contains live, replication-competent vaccinia virus, it is essential to prevent such contact to avoid accidental transmission.1