Yes, there is a vaccine for monkeypox (mpox). Two vaccines are approved in the United States for prevention: JYNNEOS and ACAM2000. In practice, JYNNEOS is the one that has been used during recent outbreaks and is the primary option offered to people at high risk.
JYNNEOS: The Primary Mpox Vaccine
JYNNEOS, manufactured by Bavarian Nordic, is fully licensed in the U.S. for adults 18 and older. It’s a two-dose series given four weeks (28 days) apart. If you miss the window for your second dose, you should still get it as soon as possible rather than restarting the series. The same vaccine is sold under different brand names internationally: Imvamune in Canada and Imvanex in Europe.
Unlike older smallpox vaccines, JYNNEOS uses a modified virus that cannot replicate in your body. That makes it significantly safer for people with weakened immune systems, skin conditions like eczema, or other health concerns that would rule out older vaccine options.
How Well JYNNEOS Works
A single dose of JYNNEOS provides roughly 58% overall effectiveness at least 14 days after vaccination. That number varies significantly depending on immune status. In people without HIV, one dose was about 84% effective. In people living with HIV, effectiveness dropped to around 35%.
Two doses appear to offer even stronger protection. In one study, no mpox cases occurred among the 211 people who received both doses, though that sample was too small to calculate a precise effectiveness number. The takeaway: completing the full two-dose series matters, especially if you have HIV or another condition that affects immune function.
How the Vaccine Is Given
JYNNEOS can be administered two ways. The standard method is a subcutaneous injection (into the fat layer beneath the skin) using a 0.5 mL dose. During the 2022 outbreak, when vaccine supply was limited, the FDA authorized an alternative: an intradermal injection (between the layers of skin, typically on the forearm) using just one-fifth the volume at 0.1 mL per dose. Studies from the National Institutes of Health found that this smaller intradermal dose produced a very similar immune response to the full subcutaneous dose, which allowed the existing supply to stretch five times further.
Both methods require two doses spaced 28 days apart.
Side Effects
JYNNEOS side effects are generally mild. The most common reactions are redness, soreness, swelling, and itching at the injection site. Some people also experience fatigue, headache, or muscle pain. These reactions are typical of many vaccines and tend to resolve on their own.
Who Should Get Vaccinated
The vaccine is recommended for people at high risk of mpox exposure. During the 2022 outbreak, this primarily included men who have sex with men and who had multiple or anonymous sexual partners, people with known exposure to someone with mpox, and laboratory workers who handle the virus. The vaccine can also be given after a known exposure. Getting vaccinated soon after contact with an infected person can help prevent or reduce the severity of illness.
Under an Emergency Use Authorization issued in August 2022, JYNNEOS can also be given to people younger than 18 who are at high risk, though the standard license covers adults only.
ACAM2000: The Older Alternative
ACAM2000 is technically approved for smallpox prevention and has been made available for mpox use under a special investigational protocol that requires informed consent and additional paperwork. It’s rarely used in practice, and for good reason: it carries substantially more risk than JYNNEOS.
ACAM2000 uses a live virus that can replicate, which means it can cause serious complications including heart inflammation (myocarditis and pericarditis), brain swelling, and severe skin infections. Fatal heart events have been reported. The live virus can also spread from the vaccinated person to close contacts through the vaccination site lesion, putting household members and intimate partners at risk of the same complications.
People with heart disease, weakened immune systems, eczema (even a past history of it), and pregnant individuals face the highest risk of serious reactions. For most people seeking mpox protection, JYNNEOS is the safer and more practical choice.
Availability Outside the U.S.
The same core vaccine used in JYNNEOS is available globally under different names. The World Health Organization has issued interim guidance on the MVA-BN vaccine platform, which covers all three licensed brands: JYNNEOS (U.S.), Imvamune (Canada), and Imvanex (Europe). All three are manufactured at the same Bavarian Nordic facility using the same process. Availability varies by country, and some regions have faced supply constraints, particularly during outbreak surges.