ACAM2000 Vaccine

General Information

  • ACAM2000 vaccine is approved to help protect against smallpox and has been made available to prevent monkeypox. ACAM2000 is an alternative to the JYNNEOS vaccine.
  • ACAM2000 vaccine is recommended as a single dose given by multiple pricks to the skin using a special needle.
  • You are considered vaccinated against monkeypox 28 days after getting the single vaccine dose.
  • CDC will work with jurisdictions that request ACAM2000 vaccine to help decide who is eligible to receive it, and to make sure people who are considering getting the vaccine are fully informed of its benefits and risks before they receive it.
  • ACAM2000 vaccine contains a live virus called Vaccinia virus that can be spread to others. Vaccinia virus is in the same family of viruses as the viruses that cause monkeypox or smallpox, which is why it can help protect against monkeypox.
  • Following vaccination, a lesion or sore (known as a “take”) will form at the site of the vaccination. The lesion may take up to several weeks or more to heal. If you get ACAM2000, you need to take special care of the lesion site to prevent spread of the Vaccinia virus to others or to other parts of your body during this time.
  • Learn more about how vaccines work and get more technical information on ACAM2000.

Vaccine Effectiveness

  • While we expect the vaccines currently being used to help protect against monkeypox will be effective, we have not previously had an outbreak of monkeypox like the current outbreak before.
  • To better understand the benefits and risks of these vaccines in the current monkeypox outbreak, CDC is working with its partners to collect data on vaccine safety and vaccine effectiveness.
  • Learn more about how vaccines work.

Long-Term Protection

  • We do not know how long protection might last, or if protection might decrease over time.

People Who Should Not Get Vaccinated

  • You should not get the ACAM2000 vaccine if:
    • You have a weakened immune system from any cause, including HIV infection, due to the increased risk of severe side effects. Learn more about monkeypox and people with HIV.
    • You are pregnant or breastfeeding.
    • You have a heart condition, skin conditions like eczema, psoriasis, or dermatitis, or if you have an eye disease treated with topical steroids.
    • You have a history of a severe allergic reaction after a previous dose or component of ACAM2000 vaccine.
    • You should also not get it if you cannot safely isolate from others who live in your home who have these same medical conditions.
  • Infants under 12 months of age should not get the ACAM2000 vaccine.

What to Expect When You Get the Vaccine

  • Like any vaccination, you will likely have to fill out paperwork before you get your vaccine.
  • ACAM2000 vaccine is given by pricking the skin surface multiple times, usually on the upper arm. A lesion (sore), called a “take,” should develop at the site of the skin prick. This is normal. The virus growing in the lesion is not monkeypox or smallpox, but it is a virus called Vaccinia. To avoid spreading the Vaccinia virus to other parts of the body or to other people, you should take special care of the lesion.

Simultaneous Immunizations

  • If you get ACAM2000 vaccine then you should not get a live injectable vaccine (such as measles, mumps, and rubella vaccine (MMR) or varicella vaccine (chickenpox)) on the same day. They should be separated by at least 28 days.
  • Consider delaying other vaccinations when getting an ACAM2000 vaccine.
  • COVID-19 vaccines may be delayed by 4 weeks if the ACAM2000 vaccine is given first.

Side Effects

  • ACAM2000 vaccine has been shown to have more frequent side effects than JYNNEOS vaccine.
  • Side effects of ACAM2000 vaccine can include redness and itching at the spot where the vaccine is given, swollen glands, headache, tiredness, fever, and muscle aches. Skin rashes may also occur following vaccination.

Adverse Events