The JYNNEOS vaccine is a two-dose mpox vaccine recommended for people at increased risk of exposure, with the second dose given 28 days after the first CDC vaccines. It can also be used after a known exposure (post-exposure prophylaxis), and the sooner you get it, the better. It's the main way to prevent mpox.
with the right treatment
testing, not symptoms, decides
| Item | Value |
|---|---|
| Curable? | yes — with the right treatment |
| Tested by | exam + lab |
| If you may have it | get tested — testing, not symptoms, decides |
How to prevent mpox
Mpox is caused by the monkeypox virus, a relative of smallpox. The clade II strain drove the outbreak that began in 2022, spreading mainly through close skin-to-skin contact, including intimate and sexual contact, and affecting mostly men who have sex with men CDC about mpox. Because it spreads through close physical contact rather than a single fluid, prevention layers several things together.
The most effective tools, in rough order of how much they lower your risk:
- Vaccination with JYNNEOS, which trains your immune system before exposure and is the cornerstone of prevention for anyone at increased risk.
- Avoiding skin-to-skin contact with anyone who has a new or unexplained rash. The rash itself is highly infectious and is the most common way the virus passes between people CDC prevention.
- Limiting close contact with materials a person with mpox has used — bedding, towels, clothing — because the virus survives on contaminated surfaces.
- Talking with partners about recent rashes or exposures before intimate contact, which catches the cases that have visible warning signs.
No single measure is perfect on its own. Vaccination matters so much because mpox can spread before someone realizes they have it, and a rash in a hidden spot — inside the mouth, in the rectum, on the genitals — is easy to miss.
Condoms and their limits
Condoms used every time lower risk for the classic sexually transmitted infections, and they offer some protection here too, but for mpox they're probably not enough on their own. The rash can appear on parts of the body a condom doesn't cover, like the thighs, buttocks, hands, or mouth, and infectious respiratory secretions may be present during close face-to-face contact.
Think of condoms as one useful layer. They reduce but don't eliminate mpox risk, so CDC pairs the advice to avoid skin-to-skin contact with a rash alongside condom use rather than instead of it.
Testing as prevention
Testing works differently for mpox than for infections you can carry silently. Mpox is confirmed by detecting the virus's DNA by PCR from a swab of a suspected lesion CDC clinical overview. There's no routine screening swab to catch it when you feel fine, because the test needs an actual lesion to sample.
What testing does do is confirm a diagnosis quickly once a rash appears, which lets you isolate, get evaluated for treatment, and warn recent partners before they spread it further. If you've had a possible exposure or a new rash, get evaluated promptly. For the silent infections that share symptoms or risk, a full screen still matters — you can get tested for the rest of the panel, and if you're timing it around a specific encounter, check when to test after exposure so you don't test too early.
The JYNNEOS vaccine: who should get it
JYNNEOS is a non-replicating vaccine, meaning it can't cause mpox or smallpox, which makes it suitable even for people with weakened immune systems. The full series is two doses, with the second given 28 days after the first. Protection builds in the weeks after the second dose, so plan ahead rather than expecting same-day coverage.
CDC recommends it for people at increased risk of exposure. That includes:
- Gay, bisexual, and other men who have sex with men, and transgender or gender-diverse people, who have had a new diagnosis of a sexually transmitted infection or more than one sexual partner.
- People who have had sex at a commercial venue or at an event tied to mpox transmission.
- Sexual partners of anyone in those groups.
- People whose work exposes them to orthopoxviruses, such as certain lab and healthcare staff.
Both doses count. Getting only the first dose leaves you with partial protection, so the second dose at the 28-day mark completes the series. If it's been longer than 28 days since your first dose, you don't restart — just get the second dose whenever you can.
Vaccine as post-exposure prophylaxis (PEP)
JYNNEOS can also be given after a known or suspected exposure to prevent disease or make it milder, and timing is everything. The sooner you get the first dose after exposure, the better the chance of preventing illness; given later in the window, it's more likely to reduce severity than to stop infection outright. If you think you've been exposed — a partner was diagnosed, or you had close contact with someone who had a rash — contact a clinician or health department right away rather than waiting to see if symptoms appear.
Vaccination vs. PEP at a glance
| Pre-exposure vaccination | Post-exposure (PEP) | |
|---|---|---|
| Who | People at ongoing increased risk | People with a recent known or suspected exposure |
| Goal | Build protection before any contact | Prevent or lessen illness after contact |
| Timing | Two doses, second 28 days after the first | First dose as soon as possible after exposure |
| What to do | Schedule both doses; complete the series | Call a clinic or health department immediately |
Putting it together
The strongest plan layers prevention rather than betting on one tool. If you're in a recommended group, complete both JYNNEOS doses. Around that, avoid skin-to-skin contact with anyone who has a rash, treat condoms as a helpful add-on rather than full coverage, and keep up with routine STI screening so the silent infections don't go unchecked. Routine testing catches what has no symptoms, while for mpox, prompt evaluation of any new rash is what finds it.
A quick note on differentiating lesions: a single firm, painless genital ulcer is more typical of syphilis, while mpox tends to produce multiple lesions that evolve through stages. The two can look alike early on, so don't self-diagnose — see our comparison of mpox vs syphilis sore and get any new sore swabbed.
When to see a clinician
Get evaluated promptly if you develop a new, unexplained rash or sores, especially on the genitals, anus, or mouth, or if you've had close contact with someone diagnosed with mpox. Reach out the same day after a known exposure, because the PEP vaccine window favors early action. Most people recover fully, but seek care sooner if you're immunocompromised, pregnant, or your symptoms are severe, since these are the situations where mpox is more likely to be serious.
For people who do get infected, antiviral options and supportive care exist; our page on mpox treatment covers what that looks like, including tecovirimat (TPOXX) CDC treatment. A diagnosis here is common and treatable, and clinics handle it daily.