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Quick Facts about Smallpox Vaccination

Content adapted from the Center for Disease Control and Prevention December 23, 2002. More detailed information including vaccination instructions, video displays, photographs, and adverse reaction diagnosis and management can be found online.

The vaccine
Normal reactions
Adverse reactions
Preventing contact transmission

The vaccine

  • A live virus vaccine, vaccinia, related to the smallpox virus
  • 95% effectiveness in preventing smallpox
  • High level immunity lasting 3 to 5 years
  • Vaccination within 3 days of exposure will prevent or lessen symptom severity
  • Vaccination within 4 to 7 days may offer some protection or modify symptom severity
  • Following vaccination, live virus is present at the vaccination site until the lesion has scabbed over and fallen off
    • Vaccinia virus can be transmitted to other parts of the body or to other people


Contraindications to non-emergency smallpox vaccination

  • Because the vaccinia virus can be spread to others, persons who have the following conditions, or who live with persons that have the following conditions, should not get the smallpox vaccine
    • Persons with current or past diagnosis of eczema or atopic dermatitis
    • Persons with active acute or chronic disruptive skin conditions including burns, impetigo, chicken pox, contact dermatitis, shingles, herpes, severe acne, or psoriasis
    • Persons who are immunosuppressed with conditions such as HIV/AIDS, solid organ or stem cell transplants, malignancy, leukemia, lymphoma, agammaglobulinemia, autoimmune disease or receiving immunosuppressant drugs (including inhaled steroids)
    • Persons allergic to the vaccine or any of its ingredients (may contain polymyxin B sulfate, streptomycin sulfate, chlortetracycline hydrochloride, neomycin sulfate)
    • Persons with conjunctival inflammation
    • Infants younger than 12 months
    • Women who are pregnant or plan to get pregnant
    • Women who are breastfeeding
    • Persons with a moderate to severe short-term illness

Contraindications to emergency smallpox vaccination

  • People who have been directly exposed to the smallpox virus should get the vaccine regardless of their health status


Normal reactions to smallpox vaccine

  • Normal primary reaction
    • 3-4 days: papule
    • 5-6 days: vesicle with surrounding erythema evolving into vesicle with depressed center
    • 8-9 days: well-formed pustule
    • 12+ days: pustule crusts over
    • 17-21 days: scab detaches, revealing a scar
  • Systemic symptoms (usually occur about 1 week after vaccination)
    • Arm soreness and redness at vaccination site
    • Regional lymphadenopathy
    • Low grade fever
    • Malaise, myalgia, headache, chills, nausea, fatigue
    • About 30% of recipients will feel too ill participate in normal activities
  • Normal variant reactions
    • Local satellite lesions (that are normal in appearance)
    • Lymphangitis
    • Local edema
    • Viral cellulitis (intense inflammation surrounding papule)


Adverse reactions to the smallpox vaccine

  • Serious reactions (1000 reactions per 1,000,000 vaccinations)
    • A toxic or allergic rash such as erythema multiforme
    • Accidental self-inoculation of the virus at another body site
    • Bacterial infection of the vaccination site
    • Generalized vaccinia-a rare systemic spread of the virus from vaccination site
  • Life-threatening reactions (14 to 52 reactions per 1,000,000 vaccinations with 1 to 2 deaths)
    • Eczema vaccinatum-wide spread vaccinia infection of the skin in persons with skin conditions such as eczema
    • Progressive vaccinia-ongoing skin infection and necrosis, usually in immunosuppressed persons
    • Postvaccinal encephalitis


Preventing contact transmission

  • Advise vaccinees and/or guardians that until a scab has formed:
    • Keep the vaccination site covered
    • Do not touch, scratch, or rub the vaccination site
    • Avoid person-to-person contact with susceptible persons (see contraindications)
    • Avoid touching, rubbing, or otherwise performing any maneuvers that might transfer the vaccinia virus to the eye or surrounding skin
    • Discard the vaccination site covering carefully, enclosed in a sealed plastic bag
    • After handling the vaccination site covering, thoroughly wash hands


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