Name: ACAM2000

ACAM2000 Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common
  • Feeling unusually cold
  • shivering
  • swollen, painful, or tender lymph glands in the neck, armpit, or groin
Less common
  • Agitation
  • anxiety
  • back pain
  • blindness
  • blistering, peeling, or loosening of skin
  • blue or pale skin
  • blurred vision
  • changes in vision
  • chest discomfort
  • chest pain, possibly moving to the left arm, neck, or shoulder
  • confusion
  • convulsions (seizures)
  • cough
  • diarrhea
  • difficult or labored breathing
  • dizziness
  • drowsiness
  • fast heartbeat
  • fever and chills
  • hallucinations
  • headache
  • irritability
  • itching
  • joint or muscle pain
  • loss of consciousness
  • mood or mental changes
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • shortness of breath
  • skin rash that is encrusted, scaly, and oozing
  • sore throat
  • sores, ulcers, or white spots in the mouth or on the lips
  • stiff neck
  • tightness in the chest
  • trouble breathing
  • unusual tiredness or weakness
  • vomiting
  • wheezing

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
  • Decreased ability to exercise
  • difficulty having a bowel movement (stool)
  • difficulty with moving
  • flushing or redness of the skin
  • general feeling of discomfort or illness
  • itching, pain, redness, or swelling at the vaccine site
  • muscle aching or cramping
  • muscle stiffness
  • nausea
  • rash
  • swollen joints
  • unusually warm skin

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

ACAM2000 Medication Guide

Smallpox (Vaccinia) Vaccine, Live

Please read this Medication Guide before you receive a vaccination with ACAM2000. This Guide does not take the place of talking to your healthcare provider about ACAM2000 and the smallpox disease.

What is the most important information I should know about the ACAM2000 smallpox vaccine?

  • If you are at a high risk for being exposed to smallpox, you should be vaccinated even if you have health problems, unless you have certain problems with your immune system. People who have health problems may have a higher chance of getting serious side effects from vaccination but are also those who have a higher chance of dying from the smallpox disease.
  • ACAM2000 may cause serious heart problems called myocarditis and pericarditis, or swelling of the heart tissues. In studies, about 1 in every 175 persons who got the vaccine for the first time may have experienced myocarditis and/or pericarditis. On rare occasions these conditions can result in an irregular heart beat and death. Your chances of getting heart problems from the vaccine are lower if you have already had this vaccine before. You can have myocarditis and/or pericarditis even if you have no symptoms. Call your healthcare provider or get emergency help right away if you have:
    • chest pain or pressure
    • fast or irregular heartbeat
    • breathing problems
    See "What are the possible side effects of ACAM2000?"
  • Because the vaccine has a live virus, it can spread to other parts of your body or to other people if you touch the vaccination site and then touch other parts of your body or other people. The vaccine virus can spread until the vaccination scab falls off (2 to 4 weeks after vaccination). If the virus is spread to a person who should not get the vaccine, the side effects can be very serious and life-threatening.
    See "How do I care for the smallpox vaccination site?"

What is the ACAM2000 smallpox vaccine?

ACAM2000 is a prescription vaccine used to protect people against smallpox disease. It is for use in people who have a high chance of getting the disease.

ACAM2000 contains live vaccinia virus (a "pox"-type virus) to protect against smallpox disease.

How do I care for the ACAM2000 vaccination site?

It is important to ALWAYS:

  1. Wear bandages or Band-Aids to cover the entire vaccination site.
  2. Wear sleeves to cover the site.
  3. Wash your hands, wash your hands, wash your hands.
  • When changing bandages or caring for your vaccination site, wear gloves. Use an absorbent bandage or Band-Aid to completely cover your vaccination site.
    • Change your bandage when it begins to soak through (at least every 1 to 3 days).
    • Throw away gloves and used bandages in sealed or double plastic bags. A small amount of bleach can be added to the bag to kill the virus.
  • Wear clothes with sleeves to cover the site and prevent scratching the vaccination site. It is especially important to wear a bandage and sleeves to bed to avoid scratching.
  • Wash your hands frequently with alcohol-based cleansers or soap and water.
    • Be sure to wash your hands each time you change your bandage or if you touch the vaccination site.
  • Do not use creams or ointments on the vaccination site because they will delay healing and can spread the virus.
  • Do not scratch or pick at the vaccination site.
  • You can take a bath or shower, but don't touch or scrub the vaccination site.
    • It is best to cover the vaccination site with a waterproof bandage.
    • If the vaccination site gets wet, dry the site with toilet paper and flush it. (Do not use a cloth towel because it can spread the virus.)
    • Cover the vaccination site with a loose gauze bandage after bathing to allow it to dry out.
  • Do not use a bandage that blocks air from the vaccination site. This could cause the skin at the vaccination site to soften and wear away.
  • If you exercise enough to cause sweat to drip, use a waterproof bandage on the vaccination site when exercising.
  • Wash clothing, towels, bedding or other items that may have come in contact with the vaccination site separately from other wash. Use hot water with detergent and bleach.
  • When the scab falls off, throw it away in a sealed plastic bag with a small amount of bleach. Wash your hands afterwards.

What should I avoid?

  • For 4 weeks after vaccination AND until the vaccination site has healed, you should avoid:
    • getting pregnant. Smallpox vaccine may rarely cause infection in an unborn baby if the mother is vaccinated during pregnancy. This infection usually results in stillbirth or death.
    • handling babies or breastfeeding.
    • swimming or hot tub use.
    • donating blood
    • Tuberculin (TB) testing. Smallpox vaccine may cause the TB test to give the wrong result.
  • Avoid rubbing, scratching or touching the vaccination site.
  • Until the vaccination scab falls off, do NOT:
    • have contact with people who cannot get the vaccine to prevent accidental spread of the vaccine virus. This includes physical contact and household contact. If there is someone in your household who should not get the vaccine, such as a pregnant woman, an infant, or someone who has an illness, you should not stay in the house until the vaccination scab falls off.
    • share a bed, clothes, towels, linen, or toiletries with unvaccinated people
  • We don't know if the vaccine virus can be spread to cats, dogs, or other household pets, or whether pets can spread the virus to other people in the household. Try to keep the vaccine virus from reaching your pet. See "How do I care for the smallpox vaccination site?"

General information about the safe and effective use of ACAM2000

This Medication Guide provides a summary of the most important information about ACAM2000. Medicines are sometimes prescribed for purposes other than those listed in the Medication Guide. If you would like more information or have any questions, talk to your healthcare provider. You can ask your healthcare provider for information about ACAM2000 that is written for healthcare professionals. The vaccine should not be used for a condition other than that for which it is prescribed.

What are the ingredients in ACAM2000?

ACAM2000: 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

This Medication Guide has been approved by the U.S. Food and Drug Administration.

Acambis, Inc., 38 Sidney Street, Cambridge, MA 02139

For Healthcare Professionals

Applies to smallpox vaccine: percutaneous powder for injection


Regional lymphadenopathy, myalgia, fever, nausea, and malaise occur at the height of the major reaction after vaccination, indicating the vaccination was successful. Fever commonly occurs in children after vaccination but is less common in adults. From 4 to 14 days after primary vaccination at least 70% of children have had 1 or more days of temperature greater than 100 degrees F. Fifteen to twenty percent have had temperatures greater than 102 degrees F.[Ref]


The most frequent complication is inadvertent inoculation of other sites, usually due of autoinoculation of the virus transferred from the vaccination site to other parts of the body. The face, eyelids, nose, mouth, genitalia, and rectum are most commonly involved. Autoinoculation of the eyes may cause blindness.[Ref]

Postvaccinial encephalitis, encephalomyelitis, encephalopathy, progressive vaccinia (vaccinia necrosum) and eczema vaccinatum are more severe complications that may occur following primary vaccination or revaccination. Severe disability, permanent neurological sequelae, and/or death may occur. Approximately 1 death per million primary vaccinations and 1 death per 4 million revaccinations have been reported, most often due to encephalitis or progressive vaccinia. Death has also occurred in unvaccinated contacts of vaccinated persons. Vaccinia viremia has been rarely reported after vaccination.

Vaccinia Immune Globulin may be indicated for certain vaccine complications such as eczema vaccinatum, progressive vaccinia, severe generalized vaccinia, or severe ocular vaccinia and may be obtained from the Centers for Disease Control (CDC). Physicians may contact the CDC for assistance with diagnosis and treatment of smallpox vaccine complications. Telephone: (404) 639-3670 (Monday-Friday, 8 AM-4:30 PM EST) or (404) 639-2888 (at other times).[Ref]


Healthy persons may develop generalized vaccinia with a generally self-limited vesicular or maculopapular rash within 6 to 9 days after vaccination. This condition is more serious in immunocompromised individuals.

Eczema vaccinatum appears shortly after the vaccinial lesion appears and is characterized by a high fever, malaise, generalized lymphadenopathy, and extensive vesicular and pustular eruptions. Patients with a history of atopic dermatitis have the highest risk of developing EV. The prognosis is poor and the mortality rate is high.

Progressive vaccinia (i.e., vaccinia necrosum, vaccinia gangrenosa, prolonged vaccinia, disseminated vaccinia), is characterized by a nonhealing vaccination site, painless progressive necrosis at the vaccination site, and occasionally metastasis to other parts of the skin, bones, and viscera. The distant lesions contain live vaccinia virus. Immunocompromised patients are at a greater risk. The prognosis is poor.

Vaccinia Immune Globulin (VIG) may be indicated for eczema vaccinatum or progressive vaccinia and may be obtained from the Centers for Disease Control (CDC). Physicians may contact the CDC for assistance with diagnosis and treatment of smallpox vaccine (the active ingredient contained in ACAM2000) complications. Telephone: (404) 639-3670 (Monday-Friday, 8 AM-4:30 PM EST) or (404) 639-2888 (at other times).

Hypersensitivity reactions including Stevens-Johnson syndrome and erythema multiforme have rarely been reported. The onset of symptoms (bulls-eye lesions and pruritus) is generally 10 days after vaccination.

Dermatofibrosarcoma protuberans, malignant fibrous histiocytoma, malignant melanoma, squamous cell carcinoma, basal cell carcinoma, and benign dermatofibroma have been reported in smallpox vaccination scars.

Contact spread of vaccinia from recently vaccinated military personnel has been reported.[Ref]

Dermatologic side effects have included pruritus, rash, generalized vaccinia (GV), eczema vaccinatum (EV), progressive vaccinia (PV), erythema multiforme, folliculitis, Stevens-Johnson syndrome, bacterial infections, and contact spread. In addition, precipitation of erythema nodosum in patients with leprosy, malignant tumors at the vaccination scar, discoid lupus, and localized myxedema have been reported; however, causality has not been established.[Ref]


Local side effects have included secondary pyogenic infections at the site of vaccine application. occurring approximately 5 days after vaccination. Swelling, warmth, and pain at the injection site, with peak symptoms occurring 8 to 10 days after vaccination and resolving within 24 to 72 hours, are indicative of a normal vaccination reaction.[Ref]


Hypersensitivity reactions may include persistent allergic sensitization to viral proteins even after immunity has waned. The allergy is manifested by the appearance of a papule and a small area of redness appearing within the first 24 hours after revaccination. Vesicles may appear in 24 to 48 hours, followed by scabbing. Stevens-Johnson syndrome, and erythema multiforme have also been reported.[Ref]


Ocular side effects have included mild to severe ocular vaccinia resulting from inadvertent autoinoculation and manifested by keratitis (epithelial and stromal), iritis, conjunctivitis (hyperemia, edema, membranes, focal lesions), and/or blepharitis (lid pustules, edema, hyperemia, cellulitis). Corneal scarring, disciform edema, and loss of vision have occurred in patients with vaccinial keratitis. Lymphadenopathy and fever have also been associated with ocular vaccinia. Ocular vaccinia has been reported in contacts of vaccinees.[Ref]

Trifluridine or vidarabine ophthalmic ointment have been recommended for conjunctival or corneal vaccinia infections. In addition, vaccinia immune globulin (VIG) may be considered for severe blepharitis, blepharoconjunctivitis, or keratitis (if there is a risk of vision loss). When using of VIG for keratitis, the possibility of an increased risk of corneal scar formation (associated with large doses over multiple days in animal models) should be taken into consideration. VIG is not recommended for isolated keratitis.

VIG may be obtained from the Centers for Disease Control (CDC). Physicians may contact the CDC for assistance with diagnosis and treatment of smallpox vaccine complications. Telephone: (404) 639-3670 (Monday-Friday, 8 AM-4:30 PM EST) or (404) 639-2888 (at other times).[Ref]

Nervous system

Nervous system side effects have rarely included headache, dizziness, paresthesia, vertigo, transient global amnesia, anoxic encephalopathy, polyneuropathy, cerebrovascular accident, CNS tumor, precipitation of neuritis in leprosy patients, transverse myelitis, seizures, paralysis, polyneuritis, brachial neuritis, and one case of ptosis, diplopia, slurred speech, and paresis, although causality has not been clearly established in all cases. The vaccine has also been associated with encephalitis (PVE) and encephalomyelitis (PVEM). PVE is has a sudden onset (6 to 10 days after vaccination) and is characterized by seizures, hemiplegia, aphasia, transient amnesia, generalized cerebral edema, mild lymphocytic meningeal infiltration, ganglion degenerative changes, and perivascular hemorrhages. Cerebrospinal fluid examination may demonstrate increased opening CSF pressure, monocytosis, lymphocytosis, or elevated CSF protein. PVEM is characterized by sudden onset (11 to 15 days after vaccination) of fever, headache, malaise, lethargy, vomiting, and anorexia. Symptoms may progress to unconsciousness, amnesia, confusion, disorientation, restlessness, delirium, drowsiness, seizures, urinary incontinence, urinary retention, constipation, meningismus and/or coma. Increased CSF pressure is present, but chemistry and cell count may be normal. Histopathological changes include perivenous demyelination, microglial proliferation in demyelinated areas with lymphocytic infiltration.[Ref]

PVE occurs more commonly in children less than 2 years old. The incidence in 1968 was reported as 2.9 cases per million vaccinees. The mortality rate is 25%, complete recovery occurs in 50%, and neurologic sequelae remain in 25%.[Ref]


Cardiovascular side effects have rarely included myocarditis, pericarditis, myocardial infarction, hypertension, atypical chest pain, angina, palpitations, supraventricular tachycardia, atrial dysrhythmias, symptomatic trigeminy, premature ventricular contractions, coronary artery disease, dilated cardiomyopathy, sudden death due to atherosclerotic coronary artery disease 60 days after vaccination, and chest tightness with ECG changes, although causality has not been clearly established in all cases.[Ref]

Symptoms of myopericarditis include chest pain, ECG changes, increased cardiac enzymes, and sometimes abnormal echocardiograms, and usually occur 4 to 30 days after vaccination.

Pulmonary edema and eosinophilic myopericarditis developed in a 29-year-old male 3 weeks after multiple vaccinations including smallpox vaccine.[Ref]


Musculoskeletal side effects have included osteomyelitis, arthritis, shoulder pain, and noncardiac chest pain; however, causality has not been established in all cases.[Ref]


Respiratory side effects have rarely included asthma, pneumonia, respiratory distress, and pseudomediastinum associated with scuba diving, although causality has not been clearly established.[Ref]


Genitourinary side effects have rarely included prostatitis, although causality has not been clearly established.[Ref]


Gastrointestinal side effects have rarely included cholecystitis and gastroesophageal reflux disease, although causality has not been clearly established in all cases.[Ref]

Some side effects of ACAM2000 may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

Smallpox vaccine Breastfeeding Warnings

There are no data on the excretion of smallpox vaccine antigens or antibodies into human milk. The vaccine is not recommended for lactating mothers in nonemergency situations.

Tertiary contact vaccinia has been reported in a breast-feeding infant of a wife of a vaccinee (the father). The vaccinee had a normal primary reaction on days 6 to 8 after vaccination. The mother developed vesicles on both areolas approximately 2 weeks after her husband was vaccinated, but continued to breast-feed. The infant started developing lesions 25 days after the father's vaccination, which were confirmed to be contact vaccinia. The Centers for Disease Control and Prevention have stated that it is safe for a mother to breast-feed after a close household contact is vaccinated, as long as standard precautions to prevent contact spread (handwashing, vaccination site care) are followed.