Do you have that old vaccine scar on your hand? (Smallpox Vaccine Scar) Let's find out the details!

Have you ever noticed a small, round scar on the top of your hand, or perhaps on the hands of your parents or grandparents? Most of the time, it looks like a hole dug into the skin just below the surface. Some people even call it a "smallpox scar." What exactly is this scar? Why does it form? Let's talk about it in more detail today.

What is a Smallpox Vaccine Scar?

Simply put, a smallpox vaccine scar is a small mark left on your arm after you receive a shot that protects you from smallpox. This scar is usually round in shape, but sometimes the edges can be a little uneven. It also appears to be slightly raised than the surrounding skin.

Now look, there are several types of special vaccines that cause a scar like this:

• `ACAM2000™`: This is the vaccine currently used by health workers to protect people from smallpox. However, it is not given to everyone. It is given to laboratory workers who work with certain types of viruses, and to some people in the military. Did you know? Thanks to previous vaccination programs, the virus that causes smallpox has now been almost completely eradicated from the world. Therefore, it is no longer spread anywhere in the world.
• `Dryvax®`: This is the smallpox vaccine that was used before `ACAM2000™`, before it was approved by the US Food and Drug Administration (`US Food and Drug Administration - FDA`). This vaccine was given to many people in the United States in the mid-1900s. However, it was stopped being given routinely after 1972. After that, `Dryvax®` was only given to selected groups, such as health workers and military personnel. It was not until 2008 that `Dryvax®` was completely discontinued and `ACAM2000™` was given instead.

So the scar on your hand could be caused by one of these two vaccines, especially if you're a bit older.

Why does this smallpox vaccine leave a scar?

Good question! The main reason a smallpox vaccine leaves a scar is because it causes a small infection in your skin when you get the vaccine. Don't worry, this is a controlled, intentional infection. Your body will fight the infection and defeat it. However, where this fight took place, that is, where the infection and the associated inflammation were, a small scar will remain.

The `ACAM2000™` vaccine (and the previous `Dryvax®` vaccine) is given with a special needle with a bifurcated tip. The healthcare provider dips this needle in the injection fluid and pricks the skin on your upper arm several times. This causes, as mentioned, a small `localized infection` that is limited to the injection site. This is a normal, expected effect of the vaccine. This small infection stimulates your `immune system` to build up a defense against the disease.

The most important thing is that this vaccine will not give you smallpox. This is because this vaccine is not made using the virus that causes smallpox (the `variola virus`). Instead, it uses a virus called `vaccinia virus`. This vaccinia virus is a virus that is related to the smallpox virus. So when your body builds up immunity against the vaccinia virus, it is also ready to fight the smallpox virus. Isn't it amazing?

Within three to four days after the injection, the injection site will become red, swollen, and itchy. This is called a "take." It's a sign that the injection is working. After a few days, this area will turn into a pus-filled blister, which will get bigger after about 10 days. Then it will start to dry out. As the blister heals, a scab will form over it. This is part of your skin's natural healing process. This scab will fall off between 14 and 21 days after the injection. That's where the small, pitted scar will be left.

This scar is a good sign that the vaccine was successful, that it gave you immunity against smallpox. But remember, this full immunity does not last a lifetime. Research has shown that immunity starts to wane after three to five years of vaccination. That is why some people (like laboratory workers) have to get the vaccine again and again for years to maintain full protection.

Why don't I have a smallpox vaccine scar?

If you recently got a smallpox vaccine and haven't developed a rash, it's possible that the vaccine didn't "take" as well. That is, the vaccine didn't work as expected. However, health workers usually detect this early (before you even realize you don't have a rash).

Doctors will check for "reaction" signs within the first week after the shot. That is, whether a rash develops and whether your body is responding properly. If these signs don't appear, you may need to get the shot again. Your doctor will advise you on what is best for you at that time.

Scars may still be present in people who received the smallpox vaccine years ago. Sometimes they can fade a little over time. Some people even undergo `scar revision` treatments to reduce the appearance of scars, if they wish.

Does the Mpox vaccine cause scarring?

It depends on the vaccine you get. Think about it, the viruses that cause smallpox (`smallpox`) and mumps (`mpox`) are very similar, like relatives. That's why health workers have been able to use the smallpox vaccine to protect people from mumps as well.

So, those who get the `ACAM2000™` vaccine will develop a scar as mentioned. However, healthcare workers in countries like the United States prefer to use the `JYNNEOS®` vaccine to protect against smallpox because it has a lower risk of serious side effects.

Whether or not people who receive the `JYNNEOS®` vaccine develop a rash depends on the method of administration. There are two main methods for administering the `JYNNEOS®` vaccine:

• Intradermal vaccination: This is usually given on the inside of your forehead. The doctor uses a small needle to inject the vaccine between the top two layers of your skin (the epidermis and dermis). Because your skin has many immune cells, even a small dose of the vaccine can easily stimulate those cells and help your body build up its defenses. When there is a sudden outbreak of a disease like smallpox, using small doses can help vaccinate more people.
• Subcutaneous vaccination: This is usually given in the upper arm. The doctor uses a needle to inject the vaccine into the deepest layer of your skin (the hypodermis).

Both methods are safe and effective. However, when the vaccine is given through the `intradermal` method, it can sometimes cause skin irritation and discoloration. These are usually temporary. However, some people may develop long-term scarring from this vaccine. The following people are at particular risk:

• People who have a history of severe scarring from the past.
• People with a history of developing scars called `Keloid scars`. These are raised, thickened scars that appear above the surface of the skin. They can appear red or pink. They can be the same color as your skin or a darker color.

People of black, Latino, or Asian descent, meaning those with darker skin, are at higher risk of developing keloid scars.

So, anyone who is at risk of scarring will not be vaccinated with the `intradermal` method. Instead, they will be given the `subcutaneous` method. Your doctor will talk to you about your medical history (including any history of scarring) before giving you the vaccine. They will definitely choose the method that is best for you.

Does having a smallpox vaccine scar mean you are protected from Mpox?

Your doctor is the best person to tell you whether you are protected from measles or any other infectious disease. Did you know? There are many factors that can affect your level of protection. For example:

• What vaccine did you receive (such as `ACAM2000™` or `JYNNEOS®`).
• When did you buy it?
• How long does that particular vaccine provide protection?

Your doctor can assess your immunity based on your vaccination history and the latest research on the durability of vaccines.

Another thing to remember is that just because you have a smallpox scar on your hand, it does not mean you have been vaccinated against smallpox. It is possible that some people, especially those born outside Sri Lanka, have been given the Bacille Calmette-Guérin (BCG) vaccine, which is given against tuberculosis. The BCG vaccine also leaves a scar on your hand, which is very similar to the smallpox vaccine scar.

However, these are two completely different vaccines, given against two very different viruses. You will only be protected from smallpox if you get a vaccine specifically designed and approved for it.

Many people, when they look at their smallpox vaccine scar, remember the exact day they got it. For some, it may have been decades ago, as part of a massive vaccination program to eradicate smallpox from the world. For others, it may have been something they got recently, due to the nature of their job.

No matter the time, place, or reason, a rash is a good sign that your body has built up immune defenses to protect you and others. If you have any questions about your rash or which vaccines you should get, don't hesitate to ask a healthcare provider.

The most important things to remember (Take-Home Message)

• A smallpox vaccine scar is a mark left on the hand after receiving a smallpox vaccine (ACAM2000™ or the older Dryvax®).
• This rash occurs because the body is responding to a small, controlled infection in the skin caused by the vaccine. This is a sign that the vaccine was successful.
• The smallpox vaccine does not contain the smallpox virus, but the similar `vaccinia virus`.
• If there is no scar, the vaccine may not have been "taken." Seek medical advice about this.
• Scarring from mpox vaccines (such as JYNNEOS®) depends on the method of administration (intradermal or subcutaneous) and individual factors.
• Although the BCG scar is similar to the smallpox scar, they are two different things. Just having a smallpox scar does not mean you are protected from smallpox.
• Your doctor is the best person to know the most about your immunity and vaccinations.

So, I hope you now have a better understanding of that little scar on your hand. It's not just a scar, it's also a good example of how science has advanced in protecting us from disease!

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