Smallpox is a viral infection that causes a fever and severe skin rash.

The early 20th century saw several smallpox epidemics, and the infection was fatal for about 3 out of 10 affected people. The infection left many people who survived smallpox with permanent scarring, frequently on their faces.

Smallpox is an infection of the variola virus. Scientists developed a smallpox vaccine using a live variation of a virus called vaccinia. Vaccinia does not cause smallpox, but it is very similar to the variola virus that does.

When the human body encounters vaccinia, it builds up antibodies to fight off the variola virus.

The vaccination was so effective that in the early 1950s, scientists declared that smallpox had been eradicated. In 1972, doctors discontinued smallpox vaccinations in the United States, except among people at risk of exposure to the infection — in a lab, for example.

The smallpox vaccine left behind a scar at the injection site. Keep reading for more information about the smallpox vaccine scar.

a doctor putting a plaster over a smallpox vaccine scar.Share on Pinterest
The smallpox vaccine leaves behind a distinctive mark.

A smallpox vaccine scar is a distinctive mark that smallpox vaccination leaves behind.

The scar may be round or oblong, and it may appear deeper than the surrounding skin. Usually, the scar is smaller than the diameter of a pencil eraser, though it can be larger.

In some people, smallpox vaccination scars are itchy or uncomfortable. This is part of the body's normal response to scarring.

A scar forms in response to an injury, such as the puncture involved in smallpox vaccination. As the body repairs the damage, it forms scar tissue.

In most people, this scar tissue is small. However, some people experience an inflammatory response to the injection of the vaccine, which can lead to a larger, raised scar.

A smallpox vaccination scar occurs because the vaccination causes an injury at the injection site.

Other vaccinations typically involve injecting fluid with thin needles. However, smallpox vaccination requires a different method of injection.

When administering this type of vaccination, a healthcare provider dips a two pronged — or bifurcated — needle into the vaccine fluid, then jabs the needle forcefully into the person's arm.

The body's immune system reacts to the live virus in the vaccination by creating a defense that pushes the virus out. It is this reaction that leads to the scarring.

As the body fights the infection, a scab begins to form. The scab may ooze and feel itchy and tight. This is a normal reaction to scabbing.

As the injury at the injection site heals, the scab falls off and leaves behind an area of skin that looks like a pockmark.

Typically, a person received the smallpox vaccination in the upper part of their left arm, though doctors sometimes administered these vaccines in other areas, such as the buttocks.

While most people received smallpox vaccinations without any problems, complications sometimes occurred.

However, no one has been infected with smallpox from the vaccine because the vaccine contains a different virus.

After receiving this vaccine, a person may experience mild, flu-like symptoms, including:

  • enlarged lymph nodes
  • soreness
  • a slight fever

Unlike some other vaccines, the smallpox vaccine contains a live virus. This means that people who receive the vaccine need to take extra care of their injection sites to avoid spreading the virus.

In rare cases, people experience more serious complications, such as:

  • allergic reactions
  • eczema vaccinatum, an extensive skin infection that can develop in people who already have eczema
  • a large sore that does not heal, which is more common in people with weakened immune systems
  • postvaccinal encephalitis, which involves inflammation in the brain

A person can try various methods of removing or reducing the appearance of a smallpox scar, including:

  • using sunscreen, as sun exposure can make scars more noticeable
  • using skin softening ointments and creams
  • asking a doctor about dermabrasion or skin grafting

A widespread vaccine campaign in the middle of the 20th century eradicated smallpox. As a result, smallpox vaccination is no longer a common practice in the U.S.

Typically, only people at risk of exposure, such as those who work with the virus in labs, receive smallpox vaccination.

People who have received this vaccine may experience some itchiness at the site of injection, as well as a scab and, eventually, a scar. These are normal features of the healing process.