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Carrington College Blog

Smallpox and Smallpox Vaccine

February 23, 2015

As you might have glanced from the “History of Vaccines” section, smallpox was one of the deadliest diseases known to mankind. It is a very serious, highly contagious and occasionally fatal disease. Smallpox is also the only disease so far to have been completely eradicated across the world by vaccination. The term smallpox is derived from the Latin word for “spotted” and refers to the raised bumps that appear on the face and body of an infected person.

What is smallpox?

Smallpox is an infectious disease caused by either the Variola major or the Variola minor virus. The former is the severe and most common form of smallpox, with a more extensive rash and higher fever. There are four types of variola major smallpox: ordinary (the most frequent type, accounting for 90% or more of cases); modified (mild and occurring in previously vaccinated persons); flat; and hemorrhagic (both rare and very severe). Variola major has a fatality rate of 30% (though the flat and hemorrhagic type is usually fatal). Variola minor is a less common form of smallpox, which is also much less severe, with death rates of 1% or less. Most survivors had some degree of (sometimes extensive) permanent scarring. Other deformities could include loss of lip, nose, and ear tissue. Blindness could occur as a result of corneal scarring. There is no specific treatment for smallpox disease, and the only prevention is vaccination.

Where does smallpox come from?

The beginnings of smallpox history are not exactly clear. The earliest evidence of smallpox was found in medical writings from ancient India (as early as 1500 BC), Egypt (1145 BC), and China (1122 BC), which described smallpox-like symptoms. The disease became rampant in Europe by the 16th century and the smallpox virus was spread throughout the rest of the word via exploration and colonization, until the smallpox eradication in 1977. After the eradication of natural smallpox, routine vaccination against smallpox among the general U.S. public was stopped. However, some scientists and medical professionals, as well as military personnel and first responders still receive the vaccine. In the event of bioterrorism, the U.S. government has enough vaccine to vaccinate every person in the United States in the event of a smallpox emergency.

How is smallpox transmitted?

Smallpox transmission normally occurs via direct and fairly prolonged face-to-face contact to spread the disease from one person to another. It can sometimes also can be transmitted through direct contact with infected bodily fluids or contaminated objects such as bedding or clothing. In very few cases, the disease has also been spread by the smallpox virus carried in the air in enclosed settings such as buildings or public transportation. A person with smallpox is sometimes contagious with onset of fever (prodrome phase), but the person becomes most contagious with the onset of rash. The infected person is contagious until the last smallpox scab falls off. Humans are the only natural hosts of the variola virus. Smallpox is not known to be transmitted by insects or animals

What are smallpox symptoms?

Once exposed to the virus, the incubation period lasts anywhere from 7 to 17 days. During this phase, the infected person is not contagious and usually feels fine and doesn’t have any symptoms. The first symptoms include high fever, malaise, head and body aches, and sometimes vomiting. This is called the (prodrome phase) and may last for 2 to 4 days. After that, a rash emerges first as small red spots on the tongue and in the mouth. These spots develop into sores that break open and spread the virus into mouth and throat, while the rash starts to cover all parts of the body within 24 hours. This is when the infected person is most contagious. By the third to fourth day, the rash becomes raised bumps which fill with a thick, opaque liquid with a depression in the center. The bumps turn into pustules over the course of 5 days. The pustules eventually form a scab. By the end of the second week after the rash appears, most of the sores have scabbed over. The scabs begin to fall off over the next 6 days. Most scabs will have fallen off three weeks after the rash appears. Once all scabs have fallen off, the person is no longer contagious.

What is the smallpox vaccine?

The smallpox vaccine is made from a virus called vaccinia (cowpox virus), which is related to smallpox. The smallpox vaccine history goes back to 1796 when Edward Jenner demonstrated the effectiveness of cowpox to protect humans from smallpox. The vaccine contains the live, attenuated vaccinia virus – not dead virus like many other vaccines. It’s important to note that the vaccine for smallpox does not contain the smallpox virus and cannot give you smallpox. Smallpox vaccination provides high level immunity for 3 to 5 years and decreasing immunity afterwards (immunity lasts longer if person is vaccinated again). Historically, the vaccine has been effective in preventing smallpox infection in 95% of those vaccinated. It may also substantially lessen the disease in the rare case of infection. The vaccine is given using a bifurcated (two-pronged) needle that is dipped into the vaccine solution, which then pricks the skin of the upper arm. If the vaccination is successful, a red and itchy bump develops at the vaccine site in three or four days, which becomes a blister filled with pus in the first week. The blister the drains and forms a scab in the second week, and finally the scab falls of in the third week.

What are the smallpox vaccine side effects?

There are side effects and risks associated with the smallpox vaccine. Most people experience normal, usually mild reactions that include a sore arm, fever, and body aches. In the past, about 1,000 people for every 1 million people vaccinated for the first time experienced reactions that, while not life-threatening, were serious. These reactions included toxic/allergic reaction at the site of vaccination, spread of the vaccinia virus to other parts of the body or to other people, and spread of the vaccinia virus to other parts of the body through blood. These reactions might require medical attention. Historically, between 14 and 52 people out of every 1 million people vaccinated for the first time experienced potentially life-threatening reactions to the vaccine. Based on past experience, it is estimated that 1 or 2 people in 1 million who receive the vaccine may die as a result.

Who should not get the smallpox vaccine?

People most likely to have serious side effects include people who have had, even once, skin conditions (especially eczema or atopic dermatitis), and people with weakened immune systems (such as those who have received a transplant, are HIV positive, are receiving treatment for cancer, or are currently taking medications, like steroids, that suppress the immune system). Other people who shouldn’t receive the vaccine are pregnant or breastfeeding women, children younger than 12 months of age, those allergic to the vaccine or any of its components, and those with a heart condition. Additionally, the Advisory Committee on Immunization Practices (ACIP) advises against non-emergency use of smallpox vaccine in children younger than 18 years of age and the vaccine manufacturer’s package insert states that the vaccine is not recommended for use in geriatric populations in non-emergency situations. Other risk factors include people with high blood pressure, high cholesterol, diabetes (or high blood sugar), and those who smoke cigarettes.