The mpox vaccine helps protect against mpox (formerly called monkeypox), which is a viral infection that causes a painful, blistering rash and cold-like symptoms. Because the mpox virus and the smallpox virus are similar, the vaccine can also provide immunity to smallpox (which is now eradicated worldwide).
Vaccine Type
There are 2 mpox vaccines available in the United States:
Replication-limited vaccine (also called modified vaccine Ankara or MVA)
Replication-competent vaccine
The replication-limited vaccine is a live, attenuated vaccine, which means it contains a weakened (attenuated) but still live version of the mpox virus. Because the virus in the vaccine is weakened, it cannot cause mpox infection, but it does trigger a strong response from a person's immune system (see Active immunization). It is the main vaccine used in the United States.
The replication-competent vaccine is a live vaccine made from a virus called vaccinia, which is a virus related to smallpox. Because this vaccine does not directly contain the smallpox virus, it cannot cause smallpox. However, because vaccinia is closely related to both smallpox and mpox, the vaccine can trigger a strong response to both from a person's immune system. Replication-competent vaccine is available for use against mpox in the United States under a special protocol. (See also Centers for Disease Control and Prevention [CDC]: About Smallpox Vaccines.)
Dose of and Recommendations for Mpox Vaccine
The replication-limited vaccine is given as an injection under the skin (preferably into the upper arm). Two doses are given 4 weeks apart.
The replication-competent vaccine is given by rapidly jabbing a small area 15 times with a needle that has been dipped in the vaccine vial. 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 fluid-filled spot containing pus develops between approximately 6 days and 11 days later. If it does not appear, people are given another dose.
People who should receive this vaccine
The replication-limited vaccine is recommended for adults age 18 years and older who are at high risk of mpox (or smallpox), including pregnant people. The CDC also recommends this vaccine for people who have or may have been exposed to mpox (see CDC: Mpox Vaccination).
The replication-competent vaccine is also indicated for people 1 year of age and older who are at high risk of mpox (or smallpox).
Risk factors for mpox (or smallpox) infection include the following:
People who have had more than one sex partner within the past 6 months
People who need to be evaluated or treated for a sexually transmitted infection
People who have had sex at a commercial sex venue or at a large commercial event or have had sex in exchange for money, goods, or illicit drugs
Men who have sex with men
People who work in professions where they may be exposed to blood or other potentially infectious body fluids, such as health care, custodial, or public safety workers
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
People who travel to areas where the infection is common or risk of exposure to the infection is high
Routine booster doses for either vaccine are not recommended 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.
People who should not receive this vaccine
People who have a weakened immune system or have had a serious, life-threatening allergic reaction (such as an anaphylactic reaction) to any component in the replication-limited vaccine or to a previous dose of replication-limited vaccine should not receive it.
People who have any of the following should not receive the replication-competent vaccine:
Severely weakened immune system (caused by, for example, advanced HIV infection or medications that suppress the immune system)
Skin disorders (particularly atopic dermatitis [eczema])
Eye inflammation
Heart condition
Age under 1 year
Pregnancy
Side Effects of Mpox Vaccine
Side effects are typically mild and most commonly include pain, redness, swelling, and skin thickening at the injection site.
Serious side effects occur in a few people. The heart problems myocarditis and pericarditis have rarely been reported after people have received either of the vaccines, which suggests there may be an increased risk of these problems after vaccination. Vaccine recipients should seek medical attention right away if they have chest pain, shortness of breath, or feelings of having a fast-beating, fluttering, or pounding heart after vaccination.
For more information about side effects, see the package inserts.
More Information
The following English-language resource may be useful. Please note that The Manual is not responsible for the content of this resource.
Centers for Disease Control and Prevention (CDC): Smallpox-Monkeypox vaccine information statement
