What is Smallpox Vaccine: Uses, Dosage, Side Effects and More

The smallpox vaccine is a live virus vaccine that protects against smallpox, a serious and potentially deadly disease. While smallpox was officially eradicated worldwide in 1980, this vaccine remains important for certain groups of people, including laboratory workers, military personnel, and healthcare workers who might be exposed to the virus.

You might be wondering about this vaccine because of your work situation, travel plans, or simply curiosity about this piece of medical history. Understanding how it works and what to expect can help you make informed decisions about your health.

What is the Smallpox Vaccine?

The smallpox vaccine contains a live virus called vaccinia virus, which is closely related to smallpox but much safer. This vaccine trains your immune system to recognize and fight off the actual smallpox virus if you're ever exposed to it.

The vaccine has been around since the late 1700s and was instrumental in completely eliminating smallpox from the world. Today's version is highly effective, with studies showing it can prevent smallpox in about 95% of people who receive it when given before exposure.

What is the Smallpox Vaccine Used For?

The smallpox vaccine is primarily used to protect people who have a higher risk of exposure to smallpox virus. Since smallpox no longer exists naturally, this vaccine isn't part of routine childhood immunizations like other vaccines you might be familiar with.

Your doctor might recommend this vaccine if you work in a laboratory that handles smallpox or related viruses. Military personnel deployed to certain areas may also receive it as a precautionary measure. Additionally, some healthcare workers who might respond to a bioterrorism event could be candidates for vaccination.

The vaccine can also be given after exposure to smallpox, though it works best when given within the first few days. This approach, called post-exposure prophylaxis, can still provide significant protection even after contact with the virus.

How Does the Smallpox Vaccine Work?

The smallpox vaccine works by introducing a weakened but live virus into your body, which kickstarts your immune system into action. This virus, called vaccinia, is similar enough to smallpox that your body learns to fight both viruses effectively.

Once you receive the vaccine, your immune system creates antibodies and activates special cells that remember how to fight smallpox. This memory protection typically lasts for several years, though immunity may decrease over time.

This is considered a strong vaccine because it contains a live virus, which makes it very effective but also means it can cause more noticeable side effects compared to some other vaccines. The trade-off is robust, long-lasting protection against a serious disease.

How Should I Take the Smallpox Vaccine?

The smallpox vaccine is given through a unique method called scarification, not through a regular injection like most other vaccines. Your healthcare provider will use a special two-pronged needle to make small punctures in your skin, usually on your upper arm.

Before your vaccination, you don't need to avoid food or take any special precautions. However, you should let your doctor know about any medications you're taking or health conditions you have. It's also helpful to wear a short-sleeved shirt to make the vaccination site easily accessible.

The process itself takes just a few minutes. Your healthcare provider will clean the area, apply a small drop of vaccine, and then use the bifurcated needle to make about 15 quick punctures through the vaccine drop into your skin.

After vaccination, you'll need to keep the site clean and dry, and avoid scratching or picking at it. Your doctor will provide specific instructions on how to care for the vaccination site as it heals.

How Long Should I Take the Smallpox Vaccine For?

The smallpox vaccine is typically given as a single dose, not as an ongoing treatment like some medications. Once you receive the vaccine, you'll develop immunity that can last for many years.

However, if you continue to be at risk for smallpox exposure, your doctor might recommend a booster vaccination. This usually happens every 3 to 5 years for people who work with smallpox or related viruses in laboratory settings.

The decision about whether you need additional doses depends on your specific risk factors and how much time has passed since your last vaccination. Your healthcare provider will help determine the right schedule for your situation.

What Are the Side Effects of the Smallpox Vaccine?

Most people who receive the smallpox vaccine will experience some side effects at the vaccination site, and this is actually a normal sign that the vaccine is working. The most common reaction is the development of a small bump that eventually becomes a pustule and then scabs over.

Here's what you can expect to happen at the vaccination site over the next few weeks:

• Days 1-3: A small red bump appears
• Days 4-6: The bump fills with fluid and may become itchy
• Days 7-14: The bump develops into a pustule with a depressed center
• Days 14-21: The pustule dries up and forms a scab
• Days 21-28: The scab falls off, leaving a small scar

This process is completely normal and shows that your immune system is responding appropriately to the vaccine.

You might also experience some general symptoms as your body builds immunity. These can include mild fever, tiredness, muscle aches, and swollen lymph nodes near the vaccination site. These symptoms usually appear within the first week and resolve on their own.

More serious side effects are rare but can occur. These include severe skin reactions, eye infections if the vaccine accidentally gets transferred to your eyes, and in very rare cases, inflammation of the heart or brain. People with compromised immune systems face higher risks of complications.

Who Should Not Take the Smallpox Vaccine?

Several groups of people should not receive the smallpox vaccine because they face higher risks of serious complications. If you have a weakened immune system due to HIV, cancer treatment, or certain medications, this vaccine is not recommended for you.

People with certain skin conditions should also avoid this vaccine. If you have eczema, dermatitis, or other chronic skin problems, the live virus in the vaccine could cause severe skin reactions that spread beyond the vaccination site.

The following conditions and situations typically exclude you from getting the smallpox vaccine:

• Pregnancy or plans to become pregnant within 4 weeks
• Breastfeeding
• Weakened immune system from any cause
• Current or recent skin conditions like eczema
• Heart disease, especially conditions affecting blood flow
• Eye problems involving the cornea
• Severe allergies to vaccine components

Additionally, if you live with someone who has any of these conditions, you might need to delay vaccination since the vaccine site can be contagious until it fully heals.

Your doctor will carefully review your medical history and current health status before determining if this vaccine is safe for you.

Smallpox Vaccine Brand Names

The smallpox vaccine currently available in the United States is called ACAM2000, which is manufactured by Emergent BioSolutions. This is the primary vaccine used for both pre-exposure and post-exposure prevention of smallpox.

ACAM2000 replaced an older vaccine called Dryvax, which was used for many years but is no longer produced. The newer vaccine has similar effectiveness but is manufactured using more modern methods and quality controls.

Another vaccine called JYNNEOS (also known as Imvamune or Imvanex in other countries) is also approved for smallpox prevention. This vaccine is different because it contains a modified virus that doesn't reproduce in human cells, making it safer for people with compromised immune systems.

Smallpox Vaccine Alternatives

If you cannot receive the traditional smallpox vaccine due to health concerns, JYNNEOS might be an alternative option. This vaccine uses a modified vaccinia virus that's been engineered to be safer for people with immune system problems or skin conditions.

JYNNEOS is given as two injections under the skin, spaced about 4 weeks apart. It doesn't cause the same dramatic skin reaction as the traditional vaccine and is considered safer for people who typically can't receive live virus vaccines.

However, JYNNEOS may not provide the same level of long-lasting immunity as the traditional vaccine, and it's primarily reserved for people who are at high risk but cannot safely receive ACAM2000.

For most people at risk of smallpox exposure, there isn't really a substitute for vaccination. Other measures like avoiding exposure and following safety protocols are important but cannot replace the protection that vaccination provides.

Is the Smallpox Vaccine Better Than Antiviral Medications?

The smallpox vaccine provides much stronger and longer-lasting protection compared to antiviral medications. While there are some antiviral drugs that might help treat smallpox if someone becomes infected, prevention through vaccination is far more effective.

Antiviral medications like tecovirimat (TPOXX) exist as potential treatments for smallpox, but they haven't been tested in actual smallpox cases since the disease no longer exists naturally. These medications would only be used if someone actually developed smallpox.

Vaccination works by preventing the disease entirely, while antiviral medications would only help reduce symptoms and complications after infection has already occurred. The vaccine essentially trains your immune system to stop smallpox before it can make you sick.

For people at risk of exposure, vaccination remains the gold standard for protection. Antiviral medications serve as a backup option for treatment rather than a replacement for prevention.