Drug information

What is Jynneos? What is Jynneos?

What is Jynneos?

Jynneos is a vaccine approved by the U.S. Food and Drug Administration (FDA) to prevent smallpox and mpox in adults who are at high risk for smallpox or mpox. (Smallpox and mpox are related viral infections that can cause similar symptoms, but mpox symptoms are generally milder than smallpox symptoms.)

Although Jynneos is FDA-approved for use in adults only, it may also be used to prevent mpox in people younger than 18 years of age who are at high risk for mpox. (This use is allowed through an Emergency Use Authorization [EUA]. An EUA allows FDA to speed up access to medical products during a public health emergency.)

Mpox can be an opportunistic infection (OI) of HIV. An OI is an infection that occurs more frequently or is more severe in people with weakened immune systems—such as people with HIV—than in people with healthy immune systems. To learn more about OIs, read the HIVinfo What is an Opportunistic Infection? fact sheet.

The Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents With HIV and/or the Guidelines for the Prevention and Treatment of Opportunistic Infections in Children With and Exposed to HIV include recommendations on the use of Jynneos in people with HIV.

What should I tell my health care provider before receiving Jynneos? What should I tell my health care provider before receiving Jynneos?

What should I tell my health care provider before receiving Jynneos?

Before receiving Jynneos, tell your health care provider:

  • If you are allergic to any ingredients in Jynneos or any medicines. Tell your health care provider if you have ever had any reactions to a previous dose of Jynneos or to any other vaccines, including a smallpox vaccine.
  • About any medical conditions you have or have had, including:
    • Severe or life-threatening allergies
    • A weakened immune system
    • History of fainting while receiving a vaccine
  • About any health conditions that may prevent you from receiving medicine by injection.
  • If you are pregnant or plan to become pregnant. Talk to your health care provider about the risks and benefits of receiving Jynneos during pregnancy.
  • If you are breastfeeding or plan to breastfeed. For mothers with HIV in the United States, the Guideline recommends speaking with your health care provider to discuss options for feeding your baby. Mothers with suppressed viral load have a less than 1% chance of transmitting HIV to their baby via their own milk. Although most medicines are safe to use while breastfeeding, some medicines should be avoided. Always let your health care provider know about all the medicines and supplements you are taking before you start breastfeeding.
  • About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Jynneos may interact with other medicines or supplements. For a list of medicines and supplements that may interact with Jynneos, see the drug label or ask your health care provider or pharmacist.

How is Jynneos given? How is Jynneos given?

How is Jynneos given?

A health care provider gives the Jynneos vaccine. Vaccination with Jynneos is usually given as a series of two injections, with a 4-week interval between each dose. Read any printed information that your health care provider gives you about the Jynneos vaccine.

What side effects can Jynneos cause? What side effects can Jynneos cause?

What side effects can Jynneos cause?

Jynneos may cause side effects that can be mild or serious. To learn about possible side effects of Jynneos, see the FDA drug label or talk to your health care provider or pharmacist. Tell your health care professional if you have any side effect that bothers you or that does not go away. Your health care professional may be able to tell you about ways to prevent or reduce some side effects.

You may report vaccine side effects using the Vaccine Adverse Event Reporting System online.

Where can I find more information about Jynneos vaccine? Where can I find more information about Jynneos vaccine?

Where can I find more information about Jynneos vaccine?

Last Reviewed: August 25, 2026