Anecdata, but my smallpox vaccine scar is a small, ~1cm spot.
The risk of "inadvertent autoinoculation" was my bigger concern - if you touch the site before it's fully healed, you can spread the vaccina virus to other parts of your own body. In rare cases it's been known to cause blindness. Fortunately a Tegaderm dressing kept it contained to my shoulder, but damn did it itch like crazy for those few weeks.
The risk of "inadvertent autoinoculation" was my bigger concern - if you touch the site before it's fully healed, you can spread the vaccina virus to other parts of your own body. In rare cases it's been known to cause blindness. Fortunately a Tegaderm dressing kept it contained to my shoulder, but damn did it itch like crazy for those few weeks.