Image for smallpox vaccine article Routine vaccination of Americans against smallpox stopped in 1972 after the disease was eradicated in the United States. However, in response to threats of biological warfare, the US government ordered enough smallpox vaccine to immunize the American public in the event of a smallpox outbreak. The smallpox vaccine is the most effective way to prevent smallpox, but the vaccine is not without its risks.

What Is Smallpox?

Smallpox is a serious, contagious, and sometimes fatal infectious disease that begins with a high fever, malaise, head and body aches, and sometimes vomiting. These symptoms are quickly followed by a specific rash, which spreads and progresses to raised bumps and pus-filled blisters that crust, scab, and fall off after about three weeks, leaving a pitted scar.

Smallpox is caused by the variola virus and is generally transmitted by direct contact with an infected person. It can also be spread through direct contact with infected bodily fluids or contaminated objects such as bedding or clothing.

A person with smallpox is sometimes contagious with the onset of fever, but the person becomes most contagious and very sick with the onset of rash. The infected person is contagious until the last smallpox scab falls off.

At the present time, there is no proven treatment for smallpox.

Vaccine: The Most Effective Way to Prevent Smallpox

Smallpox was eradicated from the human population in 1980 following worldwide vaccination. If another outbreak of smallpox occurred, vaccination would be used to prevent it from spreading to other people. If vaccination takes place within three days of exposure to the smallpox virus, it can prevent or significantly decrease the severity of smallpox symptoms in most people.

The smallpox vaccine is made from a virus called vaccinia , a “pox”-type virus related to smallpox, which helps the body develop immunity to smallpox. It provides high-level immunity for 3-5 years and is effective in preventing smallpox in 95% of people vaccinated.

Receiving the Smallpox Vaccine

The smallpox vaccine is given using a two-pronged needle. The needle is used to prick the skin a number of times in a few seconds. The pricking is not deep, but it causes slight bleeding and a sore spot. The vaccine is usually given in the upper arm.

Normal Reactions

If the vaccination was successful, the following signs occur:

  • In 3-4 days, a red, itchy bump develops at the vaccine site.
  • In the first week, the bump becomes a large blister, fills with pus, and begins to drain.
  • During the second week, the blister begins to dry up and a scab forms.
  • In the third week, the scab falls off and leaves a small scar.

These are normal reactions that usually go away without treatment. They tend to be stronger in those vaccinated for the first time.

Serious Reactions

In the past, about 1,000 people out of every one million people vaccinated for the first time experienced serious, but not life-threatening reactions. These reactions may require medical attention and include:

  • A vaccine rash or outbreak of sores limited to one area
  • A widespread vaccine rash
  • A toxic or allergic rash that can take various forms

Life-threatening Reactions

In the past, 14-52 people per one million people vaccinated for the first time experienced potentially life-threatening reactions. These reactions require immediate medical attention and include:

  • Eczema vaccinatum—serious skin rashes caused by widespread infection of the skin in people with skin conditions such as eczema (atopic dermatitis)
  • Progressive vaccinia (or vaccinia necrosum)—ongoing infection of skin with tissue destruction, frequently leading to death
  • Postvaccinal encephalitis—inflammation of the brain
  • Post-vaccine heart disorders

People with certain medical conditions, such as those with weakened immune systems or certain skin and heart conditions, are more likely to have reactions that are serious. The US Centers for Disease Control and Prevention (CDC) says they should not get the smallpox vaccine unless they have been exposed to smallpox.

Post-vaccine Care

After vaccination, it’s very important to follow skin care instructions for the vaccine site. Because the smallpox vaccine contains “live” vaccinia virus (not dead virus, like many other vaccines), it can spread to other parts of the body, or to other people. The vaccinia virus in the vaccine may cause rash, fever, and head and body aches. It can spread to other people by touching the vaccination site before it has healed or by touching bandages and clothing that have become contaminated with live virus from the vaccine site.

CDC Recommendations

The Centers for Disease Control and Prevention recommend the following precautions after receiving the smallpox vaccination:

  • Cover the vaccination site loosely with a gauze bandage and keep it covered until the scab falls off on its own. Change the bandage every 1-3 days.
  • Don’t put salves or ointments on the vaccination site.
  • Don’t scratch or pick at the scab.
  • Wear a shirt that covers the vaccination site as an extra precaution to prevent spread of the vaccinia virus. This is particularly important in situations of close physical contact.
  • Wash hands with soap and warm water or with alcohol-based hand rubs after direct contact with the vaccination site; the bandage; or clothes, towels, or sheets that might be contaminated with virus from the vaccination site.
  • Keep the vaccination site dry. Cover the vaccination site with a waterproof bandage when you bathe. Remember to change back to the loose gauze bandage after bathing.
  • Put the contaminated bandages in a sealed plastic bag and throw them away in the trash.
  • Keep a separate laundry hamper for clothing, towels, bedding, or other items that may have come in direct contact with the vaccine site or drainage from the site.
  • Wash clothing or any other material that comes in contact with the vaccination site, using hot water with detergent and/or bleach. Wash your hands afterwards.
  • When the scab falls off, throw it away in a sealed plastic bag and wash your hands afterwards.

People Who Should Not Get the Smallpox Vaccine

According to the CDC, people who have any of the following conditions, or live with someone who does, should NOT get the smallpox vaccine unless they have been exposed to the smallpox virus :

  • Eczema or atopic dermatitis (even if the condition is not currently active, mild, or was experienced during childhood)
  • Skin conditions such as burns , chickenpox , shingles , impetigo , herpes , severe acne , or psoriasis (until they have completely healed)
  • Weakened immune system (cancer treatment, an organ transplant, HIV , primary immune deficiency disorders, some severe autoimmune disorders and medications to treat autoimmune disorders, and other illnesses can weaken the immune system)
  • Pregnancy or plans to become pregnant within one month of vaccination

In addition, individuals should not get the smallpox vaccine if they:

  • Are allergic to the vaccine or any of its ingredients (polymyxin B, streptomycin, chlortetracycline, neomycin)
  • Are younger than 12 months of age
  • Are in a non-emergency situation and younger than 18 years of age or are 65 years of age or older
  • Have a moderate or severe short-term illness (until they are completely recovered)
  • Are currently breastfeeding
  • Are using steroid drops in their eyes (until they are no longer using the medication)

The CDC recommends that in the event of a bioterrorist event or other exposure to the smallpox virus, every exposed person should get the vaccine, regardless of their health status. Consult your physician if you have any questions about this recommendation.

Current Status of the Smallpox Vaccination

In the wake of terrorist threats of biological warfare, many healthcare and public health workers are being vaccinated so that they can protect others, in the event of a smallpox outbreak. At the moment, however, the smallpox vaccine is not available to the general public. If an outbreak occurs, there is enough smallpox vaccine to vaccinate everyone in the US. Production of new vaccine is underway, but hopefully there will never again be a need to use it.