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What You Need To Know About Smallpox...

Dear Mr. Ferzola:
Can you please send me information about the current national concerns of smallpox. I am a healthcare worker and want to know all the facts.
Thank ...

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Dear Mr. Ferzola:

Can you please send me information about the current national concerns of smallpox. I am a healthcare worker and want to know all the facts.

Thank You,
Gail B. RN

To Request A Topic, See EXPERT INFO at end of this page.

The History of Smallpox

Smallpox is a serious disease caused by the variola virus. While the disease has made people sick off and on for thousands of years, the world has not seen a case of smallpox since 1978. Successful worldwide vaccination programs made it possible to eliminate the disease. In 1972, since there was no longer a threat of smallpox, the U.S. stopped routinely vaccinating the public. Samples of the smallpox virus still exist in some laboratories around the world. Unfortunately, we don't know if some of these samples have fallen into the wrong hands. With the increasing threat of terrorism, there is now concern that smallpox could make a comeback.

How Is Smallpox Spread?

When a person infected with smallpox coughs, sneezes, or talks, air droplets containing the virus are released. Generally, prolonged close contact is required to spread the virus from one person to another. To catch the disease it is likely you would have to spend hours with an infected person. It is easier to catch measles, chickenpox, or the flu from another person than it is to become infected with smallpox. Smallpox can also be spread by touching the objects (bed linens or clothes) of a person who has the disease. You cannot get smallpox from insects or animals.

A person exposed to smallpox will usually feel fine for the first 12 to 14 days (can range from 7 to 17 days) of the disease. The first symptoms of smallpox begin with a high fever, head and body aches, and sometimes vomiting. A rash follows, which will turn into raised bumps that crust, scab, and fall off after about 3 weeks, leaving a pitted scar. A person with smallpox is contagious (can spread the disease) once the rash appears, and until all of the scabs fall off.

Preventing Smallpox

At this time there is no treatment for smallpox.

Researchers are testing drugs that can kill viruses. Cidofovir (Vistide), a drug used to fight other viral infections, looks promising, but it is still too soon to know if it will be useful for treating smallpox. Smallpox vaccination is the only way to prevent the disease. Since 1990, the main group of people given the smallpox vaccine are those who work in labs where the virus is studied.

How Safe Is The Smallpox Vaccine?

The smallpox vaccine contains a virus which is related to smallpox. The vaccine can't give you smallpox, but it can have some side effects. Some common reactions to the vaccine include flu-like symptoms such as fever, headache, and muscle aches. Very bad reactions can also occur including severe skin reactions, brain inflammation (encephalitis), and infection from the virus in the vaccine. It is estimated that if 1 million people were vaccinated, about 39 would develop severe skin reactions, 12 would get encephalitis, and 1 or 2 would die.

How Long Does Smallpox Vaccination Last?

Most people over the age of 30 received a smallpox vaccination when they were young. It is not known if people vaccinated so long ago would be protected if exposed to smallpox today. It is possible that the first smallpox vaccination will provide protection for about 3 to 5 years. People who receive the smallpox vaccination a second time might be protected for a longer period.

Should I Get Vaccinated?

At this time smallpox vaccination is not available to the general public. As of Friday December 13, 2002 The military and health-care workers will be able to receive the vaccine. There is enough vaccine in case of an emergency, but the decision to allow voluntary vaccination has not been made. If you are exposed to smallpox, and you haven't been vaccinated, there will still be time to protect yourself. Vaccination within 3 days of exposure to smallpox can prevent or significantly reduce the harmful effects of the disease. Those who shouldn't receive the vaccine, unless they are exposed to smallpox, include people with skin conditions (e.g., eczema or atopic dermatitis) and people whose bodies can't fight off infections (e.g., HIV/AIDs patients, organ transplant patients, and certain cancer patients). These people have a greater chance of having a bad reaction to the vaccine. Pregnant women should avoid the vaccine because it might harm the unborn baby. Only during a smallpox outbreak will smallpox vaccination be recommended for EVERYONE. In this situation, catching smallpox would be more dangerous than any side effects from the vaccine.


Vaccinia (Smallpox) Vaccine

The following excerpts are reprinted from the Centers For Disease Control publications concerning the smallpox vaccine recommendations of the Advisory Committee on Immunization Practices.


Variola virus is the etiological agent of smallpox. During the smallpox era, the only known reservoir for the virus was humans; no known animal or insect reservoirs or vectors existed. The most frequent mode of transmission was person-to-person, spread through direct deposit of infective droplets onto the nasal, oral, or pharyngeal mucosal membranes, or the alveoli of the lungs from close, face-to-face contact with an infectious person. Indirect spread (i.e., not requiring face-to-face contact with an infectious person) through fine-particle aerosols or a fomite containing the virus was less common.

Symptoms of smallpox begin 12-14 days (range: 7-17) after exposure, starting with a 2-3 day prodrome of high fever, malaise, and prostration with severe headache and backache. This preeruptive stage is followed by the appearance of a maculopapular rash (i.e., eruptive stage) that progresses to papules 1-2 days after the rash appears; vesicles appear on the fourth or fifth day; pustules appear by the seventh day; and scab lesions appear on the fourteenth day. The rash appears first on the oral mucosa, face, and forearms, then spreads to the trunk and legs. Lesions might erupt on the palms and soles as well. Smallpox skin lesions are deeply embedded in the dermis and feel like firm round objects embedded in the skin. As the skin lesions heal, the scabs separate and pitted scarring gradually develops. Smallpox patients are most infectious during the first week of the rash when the oral mucosa lesions ulcerate and release substantial amounts of virus into the saliva. A patient is no longer infectious after all scabs have separated (i.e., 3-4 weeks after the onset of the rash).

During the smallpox era, overall mortality rates were approximately 30%. Other less common but more severe forms of smallpox included: a) flat-type smallpox with a mortality rate >96% and characterized by severe toxemia and flat, velvety, confluent lesions that did not progress to the pustular stage; and b) hemorrhagic-type smallpox, characterized by severe prodromal symptoms, toxemia, and a hemorrhagic rash that was almost always fatal, with death occurring 5-6 days after rash onset.

Vaccine Efficacy

Neutralizing antibodies induced by vaccinia vaccine are genus-specific and cross-protective for other Orthopoxviruses (e.g., monkeypox, cowpox, and variola viruses). Although the efficacy of vaccinia vaccine has never been measured precisely during controlled trials, epidemiologic studies demonstrate that an increased level of protection against smallpox persists for <5 years after primary vaccination and substantial but waning immunity can persist for >10 years. Antibody levels after revaccination can remain high longer, conferring a greater period of immunity than occurs after primary vaccination alone. Administration of vaccinia vaccine within the first days after initial exposure to smallpox virus can reduce symptoms or prevent smallpox disease.

Side Effects And Adverse Reactions (Vaccine Recipients)

Side Effects and Less Severe Adverse Reactions. In a nonimmune person who is not immunosuppressed, the expected response to primary vaccination is the development of a papule at the site of vaccination 2-5 days after percutaneous administration of vaccinia vaccine. The papule becomes vesicular, then pustular, and reaches its maximum size in 8-10 days. The pustule dries and forms a scab, which separates within 14-21 days after vaccination, leaving a scar. Primary vaccination can produce swelling and tenderness of regional lymph nodes, beginning 3-10 days after vaccination and persisting for 2-4 weeks after the skin lesion has healed. Maximum viral shedding from the vaccination site occurs 4-14 days after vaccination, but vaccinia can be recovered from the site until the scab separates from the skin.

A fever is also common after the vaccine is administered. Approximately 70% of children experience >1 day of temperatures >100 F for 4-14 days after primary vaccination, and 15%-20% of children experience temperatures >102 F. After revaccination, 35% of children experience temperatures >100 F, and 5% experience temperatures of >102 F. Fever is less common among adults after vaccination or revaccination (CDC, unpublished data, undated).

Inadvertent inoculation at other sites is the most frequent complication of vaccinia vaccination and accounts for approximately half of all complications of primary vaccination and revaccination. Inadvertent inoculation usually results from autoinoculation of vaccinia virus transferred from the site of vaccination. The most common sites involved are the face, eyelid, nose, mouth, genitalia, and rectum. Most lesions heal without specific therapy, but vaccinia immunoglobulin (VIG) can be useful for cases of ocular implantation (see Treatment for Vaccinia Vaccine Complications). However, if vaccinial keratitis is present, VIG is contraindicated because it might increase corneal scarring.

Erythematous or urticarial rashes can occur approximately 10 days after primary vaccination and can be confused with generalized vaccinia. However, the vaccinee is usually afebrile with this reaction, and the rash resolves spontaneously within 2-4 days. Rarely, bullous erythema multiforme (i.e., Stevens-Johnson syndrome) occurs.

Moderate to Severe Adverse Reactions. Moderate and severe complications of vaccinia vaccination include eczema vaccinatum, generalized vaccinia, progressive vaccinia, and postvaccinial encephalitis. These complications are rare but occur >10 times more often among primary vaccinees than among revaccinees and are more frequent among infants than among older children and adults.

Eczema vaccinatum is a localized or systemic dissemination of vaccinia virus among persons who have eczema or a history of eczema or other chronic or exfoliative skin conditions (e.g., atopic dermatitis). Usually, illness is mild and self-limited but can be severe or fatal. The most serious cases among vaccine recipients occur among primary vaccinees and are independent of the activity of the underlying eczema. Severe cases have been observed also after contact of recently vaccinated persons with persons who have active eczema or a history of eczema.

Generalized vaccinia is characterized by a vesicular rash of varying extent that can occur among persons without underlying illnesses. The rash is generally self-limited and requires minor or no therapy except among patients whose conditions might be toxic or who have serious underlying immunosuppressive illnesses (e.g., acquired immunodeficiency syndrome [AIDS]).

Progressive vaccinia (vaccinia necrosum) is a severe, potentially fatal illness characterized by progressive necrosis in the area of vaccination, often with metastatic lesions. It has occurred almost exclusively among persons with cellular immunodeficiency. The most serious complication is postvaccinial encephalitis. In the majority of cases, it affects primary vaccinees aged <1 year or adolescents and adults receiving a primary vaccination. Occurrence of this complication was influenced by the strain of vaccine virus and was higher in Europe than in the United States. The principle strain of vaccinia virus used in the United States, NYCBOH, was associated with the lowest incidence of postvaccinial encephalitis. Approximately 15%-25% of affected vaccinees with this complication die, and 25% have permanent neurological sequelae. Fatal complications caused by vaccinia vaccination are rare, with approximately 1 death/million primary vaccinations and 0.25 deaths/million revaccinations. Death is most often the result of postvaccinial encephalitis or progressive vaccinia.

Precautions And Contraindications

Before administering vaccinia vaccine, the physician should complete a thorough patient history to document the absence of vaccination contraindications among both vaccinees and their household contacts. Efforts should be made to identify vaccinees and their household contacts who have eczema, a history of eczema, or immunodeficiencies. Vaccinia vaccine should not be administered for routine nonemergency indications if these conditions are present among either recipients or their household contacts.

Screening for atopic dermatitis as a contraindication for vaccination.2 Atopic dermatitis, irrespective of disease severity or activity, is a risk factor for developing eczema vaccinatum following smallpox vaccination in either vaccinees or in their close contacts. The majority of providers do not routinely make the distinction between eczema and atopic dermatitis, particularly when describing chronic exfoliative skin conditions in infants and young children. Due to the increased risk for eczema vaccinatum, smallpox (vaccinia) vaccine should not be administered to persons with a history of eczema or atopic dermatitis, irrespective of disease severity or activity. Additionally, persons with household contacts that have a history of eczema or atopic dermatitis, irrespective of disease severity or activity, are not eligible for smallpox (vaccinia) vaccination because of the increased risk that their household contacts may develop eczema vaccinatum.

Persons with other acute, chronic, or exfoliative conditions (e.g., burns, impetigo, varicella zoster, herpes, severe acne, or psoriasis) are at higher risk for inadvertent inoculation and should not be vaccinated until the condition resolves. The literature also reports that persons with Darier's disease can develop eczema vaccinatum and therefore should not be vaccinated.

Screening for pregnancy as a contraindication for vaccination.2 Fetal vaccinia is a very rare, but serious, complication of smallpox vaccination during pregnancy or shortly before conception. Therefore, vaccinia vaccine should not be administered in a pre-event setting to pregnant women or to women who are trying to become pregnant. Before vaccination, women of child-bearing age should be asked if they are pregnant or intend to become pregnant in the next 4 weeks; women who respond positively should not be vaccinated. In addition, the potential risk to the fetus should be explained and women who are vaccinated counseled not to become pregnant during the 4 weeks after vaccination. Routine pregnancy testing of women of child-bearing age is not recommended.

Altered immunocompetence.1 Replication of vaccinia virus can be enhanced among persons with immunodeficiency diseases and among those with immunosuppression (e.g., as occurs with leukemia, lymphoma, generalized malignancy, solid organ transplantation, cellular or humoral immunity disorders, or therapy with alkylating agents, antimetabolites, radiation, or high-dose corticosteroid therapy [i.e., >2 mg/kg body weight or 20 mg/day of prednisone for >2 weeks]). Persons with immunosuppression also include hematopoietic stem cell transplant recipients who are <24 months posttransplant, and hematopoietic stem cell transplant recipients who are >24 months posttransplant but who have graft-versus-host disease or disease relapse. Persons with such conditions or whose household contacts have such conditions should not be administered vaccinia vaccine.

Screening for HIV infection as a contraindication for vaccination.2 Persons with HIV infection or AIDS are at increased risk of progressive vaccinia (vaccinia necrosum) following vaccinia vaccination. Therefore, vaccinia vaccine should not be administered to persons with HIV infection or AIDS. Before vaccination, potential vaccinees should be educated about the risk of severe vaccinial complications among persons with HIV infection or other immunosuppressive conditions; persons who think they may have one of these conditions should not be vaccinated.

Infants and children.1 Before the eradication of smallpox, vaccinia vaccination was administered routinely during childhood. However, smallpox vaccination is no longer indicated for infants or children for routine nonemergency indications.

Persons with allergies to vaccine components.1 The currently available vaccinia vaccine (i.e., Dryvax) contains trace amounts of polymyxin B sulfate, streptomycin sulfate, chlortetracycline hydrochloride, and neomycin sulfate. Persons who experience anaphylactic reactions (i.e., hives, swelling of the mouth and throat, difficulty breathing, hypotension, and shock) to any of these antibiotics should not be vaccinated. Vaccinia vaccine does not contain penicillin. Future supplies of vaccinia vaccine will be reformulated and might contain other preservatives or stabilizers. Refer to the manufacturer's package insert for additional information.

Treatment For Vaccinia Vaccine Complications

The only product currently available for treatment of complications of vaccinia vaccination is VIG, which is an isotonic sterile solution of the immunoglobulin fraction of plasma from persons vaccinated with vaccinia vaccine. It is effective for treatment of eczema vaccinatum and certain cases of progressive vaccinia; it might be useful also in the treatment of ocular vaccinia resulting from inadvertent implantation. However, VIG is contraindicated for the treatment of vaccinial keratitis. VIG is recommended for severe generalized vaccinia if the patient is extremely ill or has a serious underlying disease. VIG provides no benefit in the treatment of postvaccinial encephalitis and has no role in the treatment of smallpox. Current supplies of VIG are limited, and its use should be reserved for treatment of vaccine complications with serious clinical manifestations (e.g., eczema vaccinatum, progressive vaccinia, severe generalized vaccinia, and severe ocular viral implantation).

Contraindications To Vaccination During A Smallpox Emergency

No absolute contraindications exist regarding vaccination of a person with a high-risk exposure to smallpox. Persons at greatest risk for experiencing serious vaccination complications are also at greatest risk for death from smallpox. If a relative contraindication to vaccination exists, the risk for experiencing serious vaccination complications must be weighed against the risk for experiencing a potentially fatal smallpox infection. When the level of exposure risk is undetermined, the decision to vaccinate should be made after prudent assessment by the clinician and the patient of the potential risks versus the benefits of smallpox vaccination.


Currently, cases of febrile rash illnesses, for which smallpox is considered in the differential diagnosis, should be immediately reported to local and/or state health departments. Following evaluation by local/state health departments, if smallpox laboratory diagnostics are considered necessary, the CDC Rash Illness Evaluation Team should be consulted at 770-488-7100 or 404-639-2888. As smallpox was eradicated in 1980 and no longer occurs naturally, an initial case of smallpox must be laboratory confirmed. At this time, laboratory confirmation for smallpox is available only at CDC. Clinical consultation and a preliminary laboratory diagnosis can be completed within 8-24 hours.

To assist medical and public health personnel in evaluating the likelihood of smallpox in patients with febrile rash illnesses, CDC has developed a rash illness assessment algorithm. Poster copies of this algorithm are available from state health departments and on this website (see Orders for copies of the poster can be made at

Surveillance activities, including notification procedures and laboratory confirmation of cases, would change if smallpox is confirmed. Additional information regarding surveillance activities following laboratory confirmation of a smallpox outbreak can be found in the CDC Smallpox Response Plan and Guidelines.


Centers for Disease Control and Prevention. Vaccinia (smallpox) vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2001. MMWR 2001;50(No. RR-10):1-25.
Centers for Disease Control and Prevention. Summary of October 2002 ACIP Smallpox Vaccination Recommendations. (Accesssed November 13, 2002).
Centers for Disease Control and Prevention. Draft Supplemental Recommendations of the ACIP: Use of Smallpox (Vaccinia) Vaccine, June 2002. (Accessed November 20, 2002).
Sources (Patient Handout)

Centers for Disease Control and Prevention. Smallpox Fact Sheets.
Centers for Disease Control and Prevention. Smallpox Vaccination Clinic Guide.
Cowley G. The plan to fight smallpox. Newsweek. October 14, 2002.
Begley S. New bioterror models limit threat from smallpox attack. The Wall Street Journal. November 8, 2002.
The Mayo Clinic. Smallpox. (Accessed November 21, 2002).
Henderson DA, Inglesby TV, Bartlett JG, et al. Smallpox as a biological weapon. JAMA 1999;281:2127-37.
Frey SE, Couch RB, Tacket CO, et al. Clinical responses to undiluted and diluted smallpox vaccine. N Engl J Med 2002;346:1265-74.
Breman JG, Henderson DA. Diagnosis and management of smallpox. N Engl J Med 2002;346:1300-8.
December, 2002