Mpox Vaccine

There are 2 mpox vaccines available in the United States:

• Replication-limited vaccinia virus vaccine (also called modified vaccine Ankara, MVA)

• Replication-competent vaccinia virus vaccine

The MVA vaccine contains live, attenuated vaccinia virus that does not reproduce in the person who receives it. It is the main vaccine used in the United States in the current outbreak.

The replication-competent vaccinia virus vaccine contains live vaccinia virus, which is related to the smallpox virus and provides cross-immunity to the mpox and smallpox viruses. It is available for use against mpox in the United States under an Expanded Access Investigational New Drug protocol.

The MVA vaccine is the first-line vaccine indicated for the prevention of mpox (and smallpox) in adults ≥ 18 years of age who are at high risk of mpox (or smallpox). The Centers for Disease Control and Prevention (CDC) recommends this vaccine for people, including pregnant patients, at high risk of exposure to mpox or after a recent known or presumed exposure to mpox.

The replication-competent vaccinia virus vaccine is also indicated for people ≥ 1 year of age who are at high risk of mpox (or smallpox). However, it is not the first-line vaccine recommendation for either prevention or postexposure prophylaxis.

Risk factors include the following:

• Sexually active people who are not in a long-term, mutually monogamous relationship (eg, > 1 sex partner during the previous 6 months)

• Need for evaluation or treatment of a sexually transmitted infection (eg, chlamydia, gonorrhea, syphilis)

• Sex at a commercial sex venue or at a large commercial event; sex in exchange for money, goods, or illicit drugs

• Men who have sex with men

• Occupational exposure to blood or other potentially infectious body fluids (eg, health care workers, laboratory personnel)

• Household contact and/or sexual contact with a person who has mpox

• Known or suspected exposure a person who has mpox or who has any of the above risk factors

• Travel to endemic areas

Vaccination is recommended for people who have sexual risk factors for mpox provided they have not been diagnosed with the disease during the current outbreak and have not already received 2 doses of vaccine.

Vaccination is also recommended for people traveling to Central and East Africa, where the prevalence of disease and presumed risk of exposure is high.

Contraindications for the MVA vaccine include the following:

• Immunocompromise (as with any live vaccine)

• A severe allergic reaction (eg, anaphylaxis) after a previous dose or to a vaccine component

Severe allergic reactions (ie, anaphylaxis) to the vaccine components are theoretically possible but rare. Those with a previous anaphylactic reaction to the vaccine should in general avoid receiving further doses of the vaccine; however, repeating the dose may be considered on a case-by-case basis in those with high risk of exposure after carefully weighing the risks and benefits (1).

Contraindications for the replication-competent vaccinia virus vaccine include the following:

• Immunocompromise (such as those who have advanced HIV infection or who take immunosuppressants)

• Skin disorders (particularly atopic dermatitis)

• Eye inflammation

• Cardiac disease

• Age under 1 year

• Pregnancy

The MVA vaccine dose is 0.5 mL subcutaneous (preferably into the upper arm).

A 2-dose series is administered 4 weeks apart. A completed series is required to produce adequate immunity.

An alternative 0.1 mL intradermal regimen may be considered under an Emergency Use Authorization (EUA); however, this is not the preferred route of administration.

Although in most cases mpox vaccination is performed as a preventative measure, post-exposure prophylaxis (PEP) is also suggested when appropriate. If used as PEP, MVA ideally should be administered within 4 days of the exposure but may have benefit up to 14 days after exposure (see CDC: Mpox Vaccination).

The replication-competent vaccinia virus vaccine is administered by rapidly jabbing (holding the needle between the thumb and first finger, perpendicular to the skin, and making rapid, vigorous punctures through a droplet of the vaccine placed on the skin) a small area 15 times with a bifurcated needle. This is considered 1 dose. Then the vaccine site is covered with a dressing to prevent the vaccinia virus from spreading to other body sites or to other people. Vaccination is considered successful if a pustule develops between approximately 6 and 11 days later. If it does not appear, people are given another dose.

Routine booster vaccinations are not recommended for either vaccine at this time. However, in certain high-risk groups, such as health care workers and laboratory personnel in whom the risk of exposure is high, booster vaccination is recommended 2 to 10 years after the initial vaccination.

Adverse effects are generally mild and commonly include pain, erythema, localized swelling, and induration surrounding the site of administration.

Serious reactions may occur in < 6% of people after vaccination (1). A few cases of myocarditis and pericarditis have been reported, and post-marketing surveillance is in place to identify potential long-term sequelae.

For more information about adverse effects of these vaccines, refer to the prescribing information.

The following English-language resources may be useful. Please note that The Manual is not responsible for the content of these resources.

1. World Health Organization (WHO): Vaccines and immunization for monkeypox: Interim guidance, 16 November 2022

2. Centers for Disease Control and Prevention (CDC): Clinical Overview of Mpox