Mpox
FDA's role in mpox preparedness and response, and information about mpox (formerly referred to as monkeypox)
On this page: What’s New | Fast Facts | Vaccines | Therapeutics | mpox and Medical Devices | Additional Resources | Contact the FDA
FDA’s Role
The U.S. Food and Drug Administration plays a critical role in protecting the U.S. from chemical, biological, radiological, nuclear (CBRN) attacks, and emerging infectious disease threats.
The FDA's roles in mpox preparedness and response include:
- The FDA facilitates development and availability of medical products that can be used to diagnose, prevent, or treat mpox.
- The FDA works closely with product sponsors to clarify regulatory and data requirements necessary to rapidly advance development and availability of medical products essential to supporting response efforts.
- The FDA uses appropriate regulatory mechanisms to expedite access to medical products, such as under Emergency Use Authorization (EUA) or expanded access when circumstances warrant.
- The FDA also works with product sponsors and the scientific community to design efficient, well controlled trials to support the regulatory evaluation of investigational products.
- The FDA monitors for fraudulent products and false product claims related to CBRN and emerging infectious disease threats and takes appropriate action to protect consumers.
Fast Facts
Mpox is a rare disease that is caused by infection with mpox virus. This virus can spread to anyone through close, personal, often skin-to-skin contact.
Please see the Centers for Disease Control and Prevention’s mpox outbreak page for the latest response information.
There are two approved vaccines and a cleared diagnostic test that can be used to help address the virus. For more information see: CDC Prevention Steps. In addition, certain vaccines and diagnostic tests are authorized for emergency use.
At this time, public health authorities have not recommended the general public needs to be vaccinated against mpox. Public health authorities have only recommended select individuals receive vaccination. For example, vaccination is recommended for those who have been exposed to mpox and for individuals with certain risk factors. For more information, go to this CDC page: Mpox Vaccination Basics.
Individuals who received a smallpox vaccine may have some protection against mpox. However, there are several factors that could affect whether immunity was actually present, including the “take” (the lesion that develops at the site of inoculation) of the vaccine when administered and the time since vaccination.
Yes. Moreover, since mpox was first detected in the U.S., the FDA is working closely with the CDC, commercial laboratories, and traditional manufacturers to make mpox tests more readily available to patients and providers. For information about tests authorized for emergency use, see: Monkeypox (mpox) Emergency Use Authorizations for Medical Devices.
There is only one FDA-cleared test, the CDC’s Non-variola Orthopoxvirus Real-time PCR Primer and Probe Set (K221834), for use in CDC-designated laboratories and it uses swab samples taken directly from a lesion (rash or growth). The FDA is not aware of clinical data supporting the use of other sample types, such as blood or saliva, for mpox virus testing. For information about tests authorized for emergency use, see: Monkeypox (mpox) Emergency Use Authorizations for Medical Devices.
There are no FDA-approved treatments for mpox.
The Study of Tecovirimat for Human Mpox Virus (STOMP) clinical trial was conducted by the National Institute of Allergy and Infectious Diseases (NIAID) to evaluate the safety and efficacy of tecovirimat for treatment of clade II mpox. In December 2024, an interim data analysis from STOMP found that tecovirimat did not reduce the time to lesion resolution or pain among adults with mild to moderate clade II mpox and a low risk of developing severe disease.
Expanded access is a pathway for a patient with a serious or immediately life-threatening disease or condition to gain access to an investigational medical product for treatment outside of clinical trials when no comparable or alternative therapy options are available. For more information, see: Expanded Access.
At this time, the CDC is not aware of any mpox cases in the current outbreak that have been associated with handling or eating food.
In general, you should wash your hands after handling food packaging, after removing food from the packaging, before you prepare food for eating, and before you eat. Consumers can follow the CDC guidelines on frequent hand washing with soap and water for at least 20 seconds; and frequently clean and disinfect surfaces.
- It is always important to follow the four steps of food safety—clean, separate, cook, and chill.
mpox can spread to anyone through close, personal, often skin-to-skin contact, including:
- Direct contact with mpox rash, scabs, or body fluids from a person with mpox.
- Touching objects, fabrics (clothing, bedding, or towels), and surfaces that have been used by someone with mpox.
- Contact with respiratory secretions.
For more information, see: How Mpox Spreads | CDC.
A person with mpox can spread it to others from the time symptoms start until the rash has fully healed and a fresh layer of skin has formed. The illness typically lasts 2-4 weeks. The CDC recommends that people with mpox remain isolated at home or at another location for the duration of illness.
mpox can be spread by touching objects, fabrics (clothing or towels), and surfaces that have been used by someone with mpox.
Anyone handling, preparing and serving food should always follow safe food handling procedures, such as washing hands and surfaces often.
For more information, see: How Mpox Spreads | CDC
Vaccines
There are two FDA-approved vaccines for the prevention of smallpox and mpox disease: JYNNEOS and ACAM2000. These two vaccines are the only FDA-approved vaccines for the prevention of mpox disease.
Both vaccines contain live viruses, but cannot cause smallpox or mpox disease.
- JYNNEOS is approved for individuals 18 years of age and older determined to be at high risk for smallpox or mpox infection. It is a live virus vaccine that contains Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN), a weakened, non-replicating orthopoxvirus. It is approved for administration subcutaneously (beneath the skin), as a two-dose series, 4 weeks apart. JYNNEOS may be safely used in significantly immunocompromised individuals for whom certain live vaccines are not indicated or recommended for use.
On August 9, 2022, FDA issued an Emergency Use Authorization (EUA) for JYNNEOS to allow healthcare providers to administer the vaccine intradermally (between the layers of the skin) for individuals 18 years of age and older who are determined to be at high risk for mpox infection. The EUA also allows for use of the vaccine in individuals younger than 18 years of age determined to be at high risk for mpox infection; in these individuals JYNNEOS is administered by subcutaneous injection. For all age groups, JYNNEOS is given as a two-dose series, 4 weeks apart.- For more information on JYNNEOS, see: FDA Fast Facts: JYNNEOS, Korean, Simplified Chinese, Spanish, Tagalog, Vietnamese
- For more information on the intradermal JYNNEOS vaccine, see: Intradermal JYNNEOS Monkeypox [mpox] Vaccine, Simplified Chinese, Korean, Tagalog, Vietnamese, Spanish
ACAM2000 is approved for the prevention of smallpox and mpox disease in individuals determined to be at high risk for smallpox or mpox infection. Live vaccine virus is shed from the vaccination site and can be spread to other parts of the body or to other people. Therefore, appropriate care of the vaccination site is required until it is completely healed, which may take up to six weeks.
The vaccine can cause serious complications in vaccinated individuals and their close contacts to whom the virus has spread – the risks for serious vaccine side effects are greater for certain people, including those who are immunocompromised.
ACAM2000 may cause myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of tissue surrounding the heart). In studies, about 1 in every 175 persons who got the vaccine for the first time may have experienced myocarditis and/or pericarditis. Other serious side effects of ACAM2000 include swelling of the brain or spinal cord, problems with the vaccination site becoming infected, and accidental infection of the eye with the vaccine virus.
Every person who receives ACAM2000 is required to receive the Medication Guide (PDF, 278 KB) approved by FDA. A Medication Guide is necessary for safe and effective use of the vaccine because it could help prevent serious adverse events and inform the vaccine recipient of serious risks relative to benefit that could affect their decisions to be vaccinated.
The vaccines are part of the Strategic National Stockpile, overseen by the Department of Health and Human Services’ Assistant Secretary for Preparedness and Response, which helps ensure that the vaccine is accessible in the U.S. if needed.
For more information on mpox vaccines available under Emergency Use Authorization, see: mpox Vaccine EUAs
Therapeutics
There are no FDA-approved treatments for human mpox.
TPOXX (tecovirimat) and Tembexa (brincidofovir) are antivirals which were approved to treat smallpox based on the FDA’s Animal Rule regulations, which provide a pathway for approval of certain drugs and biological products when it is not ethical or feasible to conduct efficacy studies in humans, for example, in the case of smallpox where the disease has been eradicated (21 CFR 314.600-650 and 21 CFR 601.90-95). Under the Animal Rule, adequate and well-controlled animal studies can establish the drug or biological product is reasonably likely to produce clinical benefit in humans. The Animal Rule is not a viable regulatory pathway to approve drugs for the treatment of mpox as it has been both feasible and ethical to conduct clinical trials in humans since tecovirimat was first approved as a treatment for smallpox.
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TPOXX (tecovirimat):
In 2018, the FDA approved TPOXX for treatment of smallpox in adults and children under the Animal Rule. Approval was based on efficacy data obtained from animal studies, specifically non-human primates infected with mpox virus and rabbits infected with rabbitpox virus. Such studies were relevant since the viruses that cause smallpox, mpox, and rabbitpox are in the same family of viruses called “orthopoxviruses.” Safety data was obtained in healthy human volunteers administered TPOXX.
Before 2022, no therapeutics had been evaluated in randomized, controlled trials in people with mpox. Conducting randomized, controlled trials to assess TPOXX’s safety and efficacy in humans with mpox has been an important part of the mpox response.
An initial analysis of data from the PALM007 trial, an NIH-sponsored, randomized, placebo-controlled trial of TPOXX in the Democratic Republic of the Congo, a country where mpox is endemic, found the antiviral drug did not reduce the duration of mpox lesions among children and adults with clade I mpox.
The Study of Tecovirimat for Human Mpox (STOMP)External Link Disclaimer clinical trial was conducted by the National Institute of Allergy and Infectious Diseases (NIAID) to evaluate the safety and efficacy of tecovirimat for treatment of clade II mpox (i.e., the clade that has been detected in the U.S. since 2022). STOMP was opened in September 2022. In December 2024, an interim data analysis from STOMP found that tecovirimat did not reduce the time to lesion resolution or pain among adults with mild to moderate clade II mpox and a low risk of developing severe disease.
Use of tecovirimat under CDC’s expanded access protocol (EA-IND) should be consistent with CDC’s guidelines for tecovirimat use.
Viruses can change over time. Sometimes these changes make antiviral drugs less effective at combating the virus they are targeting, meaning those drugs won’t work as well or might not work at all.
TPOXX works by inhibiting a viral protein, called VP37, that all orthopoxviruses (e.g., smallpox virus, mpox virus, vaccinia virus) share. However, as noted in the drug label, TPOXX has a low barrier to viral resistance. This means small changes to the VP37 protein could have a large impact on the antiviral activity of TPOXX.
CDC scientists are actively monitoring for changes in the mpox virus that could make the virus less susceptible to TPOXX. Because of the potential for the virus to become resistant to TPOXX, it is important the drug be used in a judicious manner.
On September 12, 2022, the FDA released additional information in publicly posted reviews supporting approval of the new drug application for tecovirimat to describe specific changes in the VP37 proteins of orthopoxviruses (e.g., vaccinia virus and mpox virus) that are associated with tecovirimat drug resistance.
As described in the FDA reviews, multiple independent studies characterized tecovirimat resistance development in orthopoxviruses in cell culture studies, in animal studies, and in an anecdotal human case of progressive vaccinia. These studies identified several genetic pathways for orthopoxviruses to become resistant to tecovirimat, which involves the emergence of amino acid substitutions in the viral VP37 drug target (see Table below). Many of the resistance pathways require only a single amino acid change in VP37 to cause a substantial reduction in tecovirimat antiviral activity.
Table: Orthopoxvirus VP37 Amino Acid Substitutions Associated with Tecovirimat Resistance
| Resistance Analysis Study | Amino Acid Substitutions |
|---|---|
| VP37 amino acid substitutions associated with high-level phenotypic resistance to tecovirimat in cell culture (defined as ≥10-fold increase in EC50 value) in vaccinia virus, cowpox virus or camelpox virus | Single amino acid substitutions: H238Q, N267D/S, G277C, D283G/Y, A290V, D294V, A295E, L302P/Q Combinations of amino acid substitutions: F25V+I372N, L178S+Y258C, N179H+D283G, H194N +303insSVK, N267D+I309T, N267S+I317V, G277C+I372N, D280G+D294G, A290V+L315M, K68N+Y258C+T308S, W2C+D225A+Y258C+D280G |
| VP37 amino acid substitutions detected in mpox virus infected, tecovirimat-treated nonhuman primates that succumbed to disease | H238Q, N267del/I/D/S/K, R268G, D280Y, A290V, A295E, L297ins, I372N/ILKIKNRK (mutation of stop codon and extension of reading frame) |
| VP37 amino acid substitutions detected in a tecovirimat-treated individual with progressive vaccinia virus infection | A290V, L315M |
| 1 Due to the conserved nature of VP37, tecovirimat resistance-associated substitutions in one orthopoxvirus are expected to apply to other orthopoxviruses. | |
Collectively, these studies indicate tecovirimat has a low barrier to resistance, and this must be considered in the context of the current mpox public health emergency because there is a risk that tecovirimat resistant virus could emerge and possibly spread.
The FDA is releasing this information to aid the scientific community’s genomic sequencing efforts to support national surveillance of the current mpox virus outbreak in the U.S. The FDA believes releasing this additional information will further facilitate the ability to monitor for the development and spread of tecovirimat-resistant virus and therefore is important in promoting public health.
Tembexa (brincidofovir)
In 2021, the FDA approved Tembexa for treatment of smallpox in adults and children, including neonates, under the Animal Rule. Approval was based on efficacy data obtained from animal studies, specifically rabbits infected with rabbitpox virus and mice infected with ectromelia virus. These viruses are in the same family of viruses, called “orthopoxviruses,” as smallpox and mpox. Safety data was obtained from clinical trials of Tembexa for a non-smallpox indication, primarily from patients who received bone marrow transplants.
The safety and efficacy of Tembexa to treat mpox in humans has not been established. In a trial evaluating Tembexa versus placebo for the prevention of cytomegalovirus infection in bone marrow transplant recipients, an increased risk of death was seen in patients treated with Tembexa for a longer duration than that recommended in the US product labeling for the treatment of smallpox. Other safety issues include liver toxicity, risk of birth defects, risk of cancer, and risk of male infertility. The most common side effects when using Tembexa are diarrhea, nausea, vomiting, and abdominal pain. Please refer to the US prescribing information for Tembexa for additional information on Tembexa’s safety profile.
Brincidofovir can be accessed by submitting a single-patient emergency use IND (EIND) request to the FDA. Brincidofovir can be considered for use under an EIND for treatment of human mpox disease in adults and pediatric patients (including neonates) with positive results of human mpox viral testing who:
- have severe disease OR are at high risk for progression to severe disease,
- AND meet any of the following:
- experience clinically significant disease progression while receiving tecovirimat, OR
- who develop recrudescence (initial improvement followed by worsening) of disease after an initial period of improvement on tecovirimat, OR
- are otherwise ineligible or have a contraindication† for oral or intravenous (IV) tecovirimat, OR
- are enrolled in, or eligible for, the open-label tecovirimat arm (Arm C) of the STOMP trialExternal Link Disclaimer‡, OR
- are severely immunodeficient (e.g., uncontrolled HIV infection – CD4 <200) without prior tecovirimat use can simultaneously initiate combination therapy with brincidofovir and tecovirimat [Note: for these cases, FDA encourages enrollment into the STOMP trial (Arm C)External Link Disclaimer.]
Clinicians with mpox patients for whom brincidofovir may be appropriate need to submit an EIND request to FDA. This can be done multiple ways. An electronic application that can be completed on a phone or computer allows for submission of an EIND to FDA at any time. This eRequest application can be found on the Reagan-Udall Foundation for the FDA websiteExternal Link Disclaimer. EIND requests may also be submitted by email (DDI.EIND@fda.hhs.gov) or by phone 301-796-3400 or 1-855-543-3784 during normal business hours (8 am-4:30 pm ET M-F). After 4:30 p.m. ET weekdays and all day on weekends/holidays, call the FDA Emergency Coordinator at 1-866-300-4374 or 301-796-8240 or email CDER-EIND@fda.hhs.gov and call the CDER Emergency Coordinator at 301-796-9900.
Notes:
†IV tecovirimat has a labeled contraindication in patients with severe renal impairment (defined as creatinine clearance below 30 mL/min); while there are no contraindications to oral tecovirimat, there are no available data to support oral tecovirimat administration via enteral tubing, so an intubated patient with creatinine clearance below 30 mL/min could be an example where brincidofovir may be considered.
‡If considering use in pregnant, breastfeeding, or pediatric patients, please be aware of the embryo-fetal toxicity and carcinogenicity findings as outlined in the USPI and patient labeling and ensure these were considered and discussed with each patient.
For more information: FDA Fast Facts: TPoxx, Korean, Simplified Chinese, Spanish, Tagalog, Vietnamese
Also see: Smallpox therapeutic information from the FDA.
For FDA Center for Drug Evaluation and Research (CDER) therapeutic product development questions, please contact: CDERPublicHealthEmergencyProductDevelopment@fda.hhs.gov.
Mpox and medical devices
Mpox virus diagnostic tests are used to determine if a person is infected with the virus that causes mpox. They may detect the mpox virus specifically or more generally detect non-variola orthopoxviruses, which includes mpox virus.
Information on Emergency Use Authorizations (EUAs) for in vitro diagnostics that the FDA has issued related to mpox to address the public health emergency is available on the mpox EUAs web page.
Additional information on mpox devices, including FDA-cleared and EUA-authorized tests, as well as more detailed information for test developers and health care providers, can be found at mpox and Medical Devices and FAQs on Testing for mpox.
If you suspect you had an adverse event or other problem with a medical device, please report it using the FDA’s MedWatch Online Voluntary Reporting Form.
Fraud and Misinformation
Unfortunately, during emergency situations, fraudulent products claiming to prevent, treat or cure conditions associated with the emergency almost always appear for sale. The FDA monitors for fraudulent products and false product claims related to emerging infectious disease threats and takes appropriate action to protect consumers.
You can report a fraudulent mpox product to the FDA. The page includes options for phone and online reporting in English or en Español.
You can find a list of fraudulent mpox products at the FDA’s Illegally Sold Mpox Products webpage.
Moreover, the FDA has taken significant steps to combat misinformation about FDA-regulated products being communicated online, in the news, and by high-profile public officials, celebrities, and other outlets. We continue to look for opportunities to combat misinformation head-on in ways easy for consumers to understand and communicate the potential for real harm. Find trusted health information from the FDA and our government partners. See the resources below.
Additional Resources
- U.S. Monkeypox [mpox] 2022: Situation Summary (CDC)
- Fact sheet: Biden-Harris Administration’s Monkeypox [mpox] Outbreak Response (White House, June 28, 2022)
- JYNNEOS Monkeypox [mpox] Vaccine Distribution by Jurisdiction (HHS/ASPR)
- Information for health care professionals (CDC)
- Information for laboratory personnel (CDC)
- Information for veterinarians (CDC)
- Use of JYNNEOS (Smallpox and Monkeypox [mpox] Vaccine, Live, Nonreplicating) for Preexposure Vaccination of Persons at Risk for Occupational Exposure to Orthopoxviruses: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022 (CDC MMWR)
- Monkeypox [mpox]External Link Disclaimer (WHO)
- What are Medical Countermeasures (FDA)
Contact the FDA
Consumers and general information: contact FDA
You may also call 1-888-INFO-FDA / (1-888-463-6332)
For CDER therapeutic product development questions, please contact: CDERPublicHealthEmergencyProductDevelopment@fda.hhs.gov
- 11Due to the conserved nature of VP37, tecovirimat resistance-associated substitutions in one orthopoxvirus are expected to apply to other orthopoxviruses.