What to Know About the Smallpox Vaccination Scar

Medically Reviewed by Melinda Ratini, MS, DO on May 26, 2022
Written by Shishira Sreenivas
5 min read

Before the smallpox virus was destroyed in the early 1980s, many people received the smallpox vaccine. As a result, if you’re in your 40s or older, you likely have a permanent scar from an older version of the smallpox vaccine on your upper left arm.

Although it's a harmless skin injury, you might be curious about its causes and potential treatments for removal. Here's all you need to know about the smallpox vaccination scar. 

Before the smallpox vaccine existed, variolation – direct exposure to smallpox sores – was the usual immunization method. Material from smallpox sores was inhaled or rubbed into the skin. It was hoped that this would cause a smallpox infection that could be controlled and give a person immunity in the future. The smallpox vaccination came out in the late 1700s to replace this practice. 

Between the late 1960s and the early 1980s, the World Health Organization (WHO) began a worldwide immunization effort to eradicate – or completely destroy – the virus. If you’re from a younger generation, you probably don’t have a smallpox vaccination scar. Typically, only people over 40 years of age might have the dime-sized dent on their upper left arm. This mark is a distinctive sign that you received the vaccine at some point.‌

There haven't been any smallpox cases since 1977. It's unlikely that you'll need a smallpox vaccination unless you're in the military or work on smallpox vaccination research.

To give the smallpox vaccine, doctors use a technique called the puncture method. It requires a different type of needle from the usual vaccination needle. Doctors use bifurcated needles. Bifurcated needles have two prongs, and they help deliver the vaccine to the proper depth into the skin. ‌

Getting the vaccine consists of the following steps:

  1. Dip the two-pronged needle into the vaccine suspension.
  2. Shallowly but vigorously prick the skin with the needle 15 times. 
  3. Observe the changes of the skin injury over the next few days.

What causes the smallpox vaccination scar? The vaccination technique isn’t to blame for the scar. The smallpox vaccine holds a live virus. It creates a controlled infection that forces your immune system to defend your body against the virus. The exposure to the virus tends to leave a sore and itchy bump behind. This bump later becomes a larger blister that leaves a permanent scar as it dries up. 

What happens if the vaccination spot doesn't get infected? If your vaccination spot doesn't develop a bump that fills up with pus during the first week after application, the immunization process was unsuccessful. In this unlikely situation, doctors recommend revaccinating. Your skin's reaction to a second dose will usually be milder and heal faster. 

Your smallpox vaccination spot must heal on its own for the immunization process to be successful, but certain measures can prevent the virus from spreading while the skin lesion is still fresh. After you get the vaccine, you should:

  • Cover the area with gauze and breathable bandages.
  • Make sure the cover doesn't allow liquid to escape.
  • Change the gauze and bandages every third day or whenever it gets wet.
  • Wash hands with the proper technique after touching the wound.
  • Don't let others touch the blister or the liquid it makes.
  • Do laundry separately and don’t share clothes, towels, or sheets.
  • Machine-wash infected clothes with warm water and detergent.
  • Put used bandages in a separate plastic bag before throwing away.

Possible smallpox vaccination complications. The most common complication happens when you accidentally transfer the virus from the pus-filled blister to a different body part. The areas most likely to be affected in this way are your mouth, eyes, nose, and genital area. In rare cases, this problem can cause scarring in the cornea — the clear layer covering the colored part of the eye.

‌A lesser-known complication is the appearance of aggressive skin tumors on the smallpox vaccination scar over time due to trauma. Experts call this condition dermatofibrosarcoma protuberans (DFSP). This problem is extremely rare: There have been only five documented cases in the U.S. since the 1940s.

‌People who have eczema – an inflammatory skin condition – can get an infection called eczema vaccinatum when exposed to the live virus in the vaccine. Although uncommon, this issue is potentially serious and can cause severe discomfort. If you're vulnerable to this infection, you should avoid the smallpox vaccine and skin-to-skin contact for 30 days with anyone who receives it.

Because the smallpox virus is closely related to the monkeypox virus, the smallpox vaccine can give you some protection against monkeypox. Studies show that the vaccine is about 85% effective at preventing monkeypox.

But the immunity doesn’t last forever. Research shows the first dose only protects you for about 3 to 5 years. After that, the immunity it gives you against both diseases start to dip. If you have a scar on your arm from the first generation of smallpox vaccines and you’re exposed to monkeypox, you might have a milder illness.

So, if you’re exposed to monkeypox but haven’t had the smallpox vaccine within the last 3 years, the CDC recommends getting revaccinated as soon as possible. Two smallpox vaccines are currently licensed in the U.S. to prevent smallpox: ACAM2000 and JYNNEOS (which is also known by the brand names Imvamune and Imvanex). JYNNEOS is also specifically licensed to prevent monkeypox. ACAM2000 is put into the skin by pricking the skin surface and can leave a scar at the injection site. JYNNEOS is given as a non-replicating live virus, and no sore develops.

The smallpox vaccination scar usually isn't a threat to your health. If you have one and how it looks bothers you, you can have a scar removal procedure to get rid of it. 

Your doctor may treat it like a keloid – a type of raised scar. In this case, they might recommend surgery in combination with cryotherapy – using freezing cold temperatures to destroy cells. This combination can improve your skin's condition in the affected area.