Questions & Answers
Smallpox - Vaccine Description
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  1. What is smallpox vaccine?

    Smallpox vaccine contains live vaccinia virus (not smallpox virus) to protect against smallpox. This same vaccine has been given to millions of Americans, including Service members during World War I, World War II, and until the 1980s. Between December 2002 and January 2008, more than 1.4 Million Service members received smallpox vaccination.

    The vaccine is made from a virus called vaccinia, which is another "pox"-type virus related to smallpox. The vaccine helps the body develop immunity to smallpox. The vaccine does not contain the smallpox virus and cannot spread smallpox. The vaccine was successfully used to eradicate smallpox from the human population.

    The vaccine virus (vaccinia) is similar to the smallpox virus (variola). Edward Jenner reported in 1796 that people given vaccinia (smallpox) vaccine become protected from smallpox. Smallpox vaccine was the very first vaccine and has been used successfully for over 200 years.

    Getting smallpox vaccine before exposure will protect about 95 percent of people from getting smallpox. Vaccination within 3 days after exposure will prevent or significantly lessen the severity of smallpox symptoms in the vast majority of people. Vaccination 4 to 7 days after exposure likely offers some protection from disease or may modify the severity of disease. Vaccination after this time may not offer any benefit.

  2. Is ACAM2000 the same smallpox vaccine that was used in the past?

    Both Dryvax and ACAM2000 are derived from the New York City Board of Health strain using a pox virus called vaccinia, but Dryvax was grown on the skin of calves and essentially freeze-dried for storage. Dryvax was licensed and approved by the FDA, in 1931 and is now in limited supply because it is no longer manufactured.

    ACAM2000, Smallpox (Vaccinia) Vaccine, Live, approved by FDA in 2007, is a live vaccinia virus derived from plaque purification cloning from Dryvax®, grown in African Green Monkey kidney (Vero) cells, and tested to be free of adventitious agents.

  3. How long has smallpox vaccine been around?
    Smallpox vaccination was the very first vaccination. Edward Jenner first developed it in 1796. Smallpox vaccines were first licensed in the United States in 1903. The original license for Dryvax® has been continuously in effect since 1931. FDA recently licensed a supply of smallpox vaccine made by Acambis Laboratories called ACAM2000. Smallpox vaccine used for Service members passes all tests required by the FDA.


  1. Is ACAM2000 an effective vaccine?
    Based on historical evidence, vaccinated individuals are considered protected against smallpox after a major cutaneous reaction is observed following primary vaccination. From a clinical perspective, ACAM2000 elicited a strong immune response in all study populations. ACAM2000 induced positive cutaneous responses in >96% of vaccinia-naïve subjects and in >84% of previously vaccinated subjects in pre-licensure studies.

  2. Who is the manufacturer of ACAM2000?

    Peterhouse Technology Park
    100 Fulbourn Road
    Cambridge CB1 9PT, UK

  3. What are Acambis's responsibilities to CDC and DoD?
    Acambis developed ACAM2000 under contracts with the US Centers for Disease Control and Prevention (CDC) as part of its preparations for a public health emergency. ACAM2000 is the primary smallpox vaccine for use in an emergency and forms the majority of the US Government's smallpox vaccine Strategic National Stockpile (SNS). Acambis is currently in negotiations with the CDC to provide the US Government with a long-term ACAM2000 production capability that is located entirely in the US.

  4. How will it be supplied?

    ACAM2000, Smallpox (Vaccinia) Vaccine, Live is supplied in multiple-dose 3 mL clear glass vials containing lyophilized powder (freeze-dried vaccine). After reconstitution with 0.3 mL of diluent, the vial contains approximately 100 nominal doses of 0.0025 mL of vaccinia virus (live,) 1.0 - 5.0x108 PFU/mL or 2.5-12.5x105 PFU/dose.

    Diluent for ACAM2000 is supplied in 3 mL clear glass vials containing 0.6 mL of diluent.

    Bifurcated needles are supplied in boxes (5 x 5 x 1 in) containing 100 needles.

    1 mL tuberculin syringes with 25 gauge x 5/8" needles are supplied for vaccine reconstitution.

  5. How is ACAM2000 stored and handled?

    Prior to reconstitution, ACAM2000 vaccine retains a potency of 1.0x108 PFU or higher per dose for at least 18 months when stored at refrigerated temperatures of 2-8°C (36-46°F).

    After reconstitution, ACAM2000 vaccine may be administered during a 6 to 8 hour workday at room temperature (20-25°C, 68-77°F). Do not expose ACAM2000 to room temperature conditions for more than 48 hours. Reconstituted ACAM2000 vaccine may be stored in a refrigerator (2-8°C, 36-46°F) no longer than 30 days, after which it should be discarded.

    Diluent for Smallpox Vaccine, (Vero Cells) Lyophilized, ACAM2000 should be stored in a refrigerator (2-8°C, 36-46°F). ACAM2000 contains live vaccinia virus that is transmissible, and should be handled as an infectious agent once vials are opened.

  6. Do vaccinees need signed consent to receive this vaccine?
    No, since it is FDA approved, there is no requirement for signed consent.

  7. Is there a change in the process to administer ACAM2000?
    Yes, all personnel (primary vaccinees and re-vaccinees) who receive ACAM2000 will receive 15 jabs with a bifurcated needle.

  8. If a vaccinee has a question about ACAM2000, what DoD resources are available to them?
    Immunization Healthcare Branch:
    DoD Vaccine Clinical Call Center:
    • Toll Free: 1-877-GET-VACC or (877) 438-8222

  9. Do those vaccinated with Dryvax need to be revaccinated with ACAM2000 sooner than 10 years?
    No. Personnel previously vaccinated with Dryvax have an increased level of protection against smallpox and should only be re-vaccinated IAW DoD policy. Most people will require re-vaccination after 10 years.

  10. What education information will a vaccinee receive?
    Anyone vaccinated with the smallpox vaccine will receive a DoD Smallpox Information Brochure, a Medication Guide, and additional information as requested.

  11. Is this smallpox vaccine diluted?
    The smallpox vaccine is stored as a powder and then a diluent (liquid) is added to reconstitute the powder shortly before use. The reconstituted vaccine is the same as the original full-strength concentration.

  12. Is smallpox vaccine live or synthetic?
    Smallpox vaccine is "live". It contains natural, live vaccinia viruses.

  13. How is smallpox vaccine given?
    The smallpox vaccine is not given with a typical needle. It is not a "shot" like many vaccinations. The vaccine is given using a bifurcated (two-pronged) needle that is dipped into the vaccine solution. A bifurcated needle looks like a little pitchfork or tuning fork. When dipped into the vaccine vial, the needle retains a droplet of the vaccine between the two prongs. The needle is then used to prick the skin 15 times in a few seconds. The pricking is not deep, but it will cause a sore spot and a very small drop of blood to form. The vaccine usually is given on the upper arm.

  14. Who will administer smallpox vaccine?
    Trained healthcare workers will administer the vaccine. Typically this would be a nurse or a medic.

Vaccine Ingredients

  1. What are the ingredients of smallpox vaccine?

    The vaccine contains live vaccinia virus derived from plaque purification cloning from Dryvax (Wyeth Laboratories, Marietta, PA, calf lymph vaccine, New York City Board of Health Strain) and grown in African Green Monkey kidney (Vero) cells.

    Inactive ingredients: 6-8 mM HEPES (pH 6.5-7.5), 2% human serum albumin USP, 0.5 - 0.7% sodium chloride USP, 5% mannitol USP, and trace amounts of the antibiotics neomycin and polymyxin B.

    Diluent for ACAM2000: 50% (v/v) Glycerin USP, 0.25% (v/v) Phenol USP in Water for Injection USP, 0.3 mLs.

  2. How do I obtain a PCR (polymerase chain reaction assay) for Vaccinia?
    1. PCR (polymerase chain reaction assay for vaccinia) is available through military or state regional laboratories participating in Emergency Response Lab Network. If unable to obtain prompt local support for PCR and culture, contact the Vaccine Healthcare Centers Network by email or telephone. After hours, Call DOD Vaccine Call Center: 1-866-210-6469.
    2. Information on obtaining viral PCR and culture specimens is available on the CDC website:

Vaccinations Over Time

  1. Who received smallpox vaccination in the past?

    Smallpox vaccination of US military forces dates back to 1812. Smallpox vaccine has been given to millions of Americans, including Service members during World War I, World War II, and into the 1980s.

    In the United States, routine vaccination against smallpox ended around 1972 in most places. Military smallpox vaccination programs continued longer. In 1984, routine military vaccinations were limited to recruits entering basic training. Between 1984 and 1989, some service members were immunized but not others. In 1990, the Department of Defense discontinued routine vaccination of recruits.

    Between December 2002 and January 2008 more than 1.4 M Service members received smallpox vaccination.