Vaccines for Monkeypox Prevention: Jynneos and ACAM2000

The Food and Drug Administration (FDA) has licensed 2 vaccines for the prevention of monkeypox infection: ACAM2000 (smallpox [vaccinia] vaccine, live) and Jynneos (smallpox and monkeypox vaccine, live, nonreplicating). 

In order to mitigate the spread of monkeypox, the US Department of Health and Human Services has expanded access to Jynneos for adults 18 years of age and older determined to be at high risk for monkeypox infection. 

While in ample supply, the ACAM2000 vaccine should not be used in patients who have certain health conditions including: cardiac disease or a history of cardiac disease; eye disease treated with topical steroids; congenital or acquired immune deficiency disorders, including those taking immunosuppressive medications; eczema and persons with a history of eczema or other acute or chronic exfoliative skin conditions; infants less than 12 months of age; and pregnant individuals. These patients may be at greater risk of adverse events including severe disability, permanent neurological sequelae and/or death. 

Patients who are at risk for severe adverse events with ACAM2000 or severe disease from monkeypox should be prioritized to receive Jynneos. 

An individual is considered fully vaccinated about 2 weeks after the second dose of Jynneos and 4 weeks after receiving ACAM2000. According to the CDC, there are currently no data available on the effectiveness of these vaccines during the 2022 monkeypox outbreak. 

Jynneos ACAM2000
Company Bavarian Nordic, Inc. Emergent BioSolutions Inc.
Generic Name and Formulation Smallpox and monkeypox vaccine, live, non-replicating; contains 0.5–3.95×108 infectious units of MVA-BN live virus; per 0.5mL dose; suspension for subcutaneous (SC) injection; preservative-free. Smallpox (vaccinia) vaccine, live; contains 2.5–12.5×105 plaque forming units; per 0.0025mL dose; lyophilized powder for percutaneous scarification after reconstitution; contains trace amounts of neomycin, polymyxin B.
Pharmacological Class Vaccine. Vaccine.
Indication Prevention of smallpox and monkeypox disease in adults determined to be at high risk for smallpox or monkeypox infection.

Active immunization against smallpox disease for persons determined to be at high risk for smallpox infection.


Allowed for use against monkeypox under an Expanded Access IND.


≥18yrs: Give by SC injection, preferably into the upper arm (deltoid).


Administer 2 doses (0.5mL each) 4 weeks apart.


Immune response takes 2 weeks after the second dose for maximum development.


<18yrs: not established.

See full labeling for instructions on vaccine preparation, administration, site care, and interpretation of response to vaccination.


≥17yrs: Give by percutaneous route (scarification) into the upper arm (deltoid) only after proper training.


Clean the injection site area using an alcohol swab(s), if necessary. Allow skin to dry thoroughly to prevent inactivation of the live vaccine virus by the alcohol.


Pick up a droplet (0.0025mL) of reconstituted vaccine solution using a bifurcated needle and deposit onto the vaccination site. Rapidly make 15 jabs of the needle perpendicular to the skin through the droplet to puncture skin, within a diameter of about 5mm.


Vaccination site may be covered with loose gauze bandage or semipermeable dressing.


Immune response takes 4 weeks for maximum development.


Repeat vaccination every 3 years in those at continued high risk of exposure.


<17yrs: not established.

Contraindications None. Severe immunodeficiency, including those who are undergoing bone marrow transplantation or those with primary or acquired immunodeficiency who require isolation.
Boxed Warning None.

Risk for serious complications including: myocarditis and/or pericarditis in healthy adults; encephalitis, encephalomyelitis, encephalopathy, progressive vaccinia, generalized vaccinia, severe vaccinial skin infections, erythema multiforme major (including Stevens-Johnson Syndrome), eczema vaccinatum resulting in permanent sequelae or death, ocular complications, blindness, and fetal death following either primary vaccination or revaccination.


Increased risk of these complications, which may result in severe disability, permanent neurological sequelae and/or death, with the following conditions: cardiac disease or history of, eye disease treated with topical steroids, congenital or acquired immune deficiency disorders (including those taking immunosuppressants), eczema or history of, other exfoliative skin conditions, infants <12mos of age, pregnancy.


Risk of transmitting live vaccinia virus to persons who have close contact with the recipient; the risks in close contacts are the same as the recipient. Weigh risk of serious vaccination complications against the risk of a potentially fatal smallpox infection

Warnings and Precautions

Have appropriate medical treatment available to manage possible anaphylactic reactions.


Immunocompromised: may have diminished immune response.


Vaccination may not protect all recipients.

Pregnancy: available data insufficient to inform vaccine-associated risks.


Nursing mothers: data not available to assess effects in breastfed infant or on milk production; consider clinical need vs potential adverse effects.


Elderly: studies did not include sufficient number to determine difference in response compared with younger patients.

See Boxed Warning.


Known cardiac disease (eg, previous MI, angina, CHF, cardiomyopathy, chest pain, shortness of breath with activity, stroke or TIA, other heart conditions).


Diagnosed with ≥3 risk factors for ischemic coronary disease (eg, high BP, elevated blood cholesterol, diabetes, family history of heart condition <50yrs of age, smokers).


Accidental infection of the eye may result in ocular complications (eg, keratitis, corneal scarring, blindness).


Do not inject by the intradermal, SC, IM, or IV route.


Avoid contact with skin, eyes, or mucous membranes.


Avoid blood and organ donation for at least 30 days after vaccination.


Vaccination may not protect all recipients.


Children: may be associated with increased risk of serious complications, especially in infants <12 months old.


Elderly (>65yrs): not studied.


Pregnancy: may cause fetal infection, resulting in stillbirth or death.


Nursing mothers: can be transmitted to infants.

Drug Interactions None.

Concomitant use with corticosteroid eye drops may increase risk of ocular complications.


May induce false (+) tests for syphilis.


May induce false (–) results for tuberculin skin test, and possibly, blood tests for tuberculosis; if possible, delay tuberculin test for 1 month after vaccination.


Do not put salves or ointments on the vaccination site.

Adverse Reactions

Most common in vaccine-naïve healthy adults: Injection site reactions (eg, pain, swelling, redness, induration, itching), muscle pain, headache, fatigue, nausea, and chills.


Most common in previously vaccinated healthy adults: Injection site reactions (eg, redness, pain, induration, swelling, itching), fatigue, headache, and muscle pain.

Common: Inoculation site signs/symptoms, lymphadenitis, and constitutional symptoms (eg, malaise, fatigue, fever, myalgia, headache).


Inadvertent inoculation at other sites is the most frequent complication. Most common sites: face, nose, mouth, lips, genitalia and anus.


Self-limited skin rashes not associated with vaccinia replication: urticaria and folliculitis.

How Supplied Single-dose vials—20.

Multiple-dose vial (3mL)—1 (w. bifurcated needles, tuberculin syringes).


After reconstitution with 0.3mL of diluent, the vial contains approximately 100 nominal doses of 0.20025mL of vaccinia virus (live).


  1. Monkeypox: Vaccines. Centers for Disease Control and Prevention. Accessed July 26, 2022.
  2. Jynneos. Package insert. Bavarian Nordic, Inc.; 2022. Accessed July 26, 2022.
  3. ACAM2000. Package insert. Emergent BioSolutions Inc.; 2022. Accessed July 26, 2022.