Smallpox vaccine Side Effects

It is possible that some side effects of smallpox vaccine may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to smallpox vaccine: injection powder for solution, injection powder for suspension

As well as its needed effects, smallpox vaccine may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking smallpox vaccine, check with your doctor immediately:

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 smallpox vaccine side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned 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

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.


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.

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).


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 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.

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.


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.


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.


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.

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).

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.

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%.


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.

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.


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


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


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


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

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