One of the smallpox vaccines available in the United States can also offer protection against mpox (aka monkeypox). But if you got a smallpox shot as a child, you’re probably no longer protected.

Mpox, formerly known as monkeypox, is transmitted through close contact with a person or animal with the virus. It causes a skin rash and flu-like symptoms, such as fever and chills.

The smallpox vaccine helps protect against mpox. Keep reading for an overview of frequently asked questions.

Monkeypox vs. smallpox

Mpox and smallpox both belong to a family of viruses known as orthopoxviruses. They have similar makeup and characteristics, and as a result, cause similar symptoms.

Smallpox was extremely deadly. Mpox is much milder than smallpox. It usually resolves on its own after a couple of weeks and is rarely fatal.

The World Health Organization declared smallpox eradicated in 1980 after a worldwide vaccination campaign.

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Smallpox vaccines stimulate the production of antibodies that can recognize other orthopoxviruses, including mpox. As a result, smallpox vaccines also offer protection against mpox.

There are currently two smallpox vaccines available in the United States:

  • JYNNEOS vaccine: The Food and Drug Administration (FDA) approved the JYNNEOS vaccine to protect against both smallpox and mpox in 2019. It’s currently the first line of protection against mpox in the United States.
  • ACAM2000 vaccine: Since 2007, the ACAM2000 vaccine has been FDA approved to protect against smallpox. But it is not FDA approved for use against mpox. Still, people in high risk populations may use it under the FDA’s expanded drug access program.

According to a 2022 review, both vaccines provide significant protection against mpox infection. But JYNNEOS is less likely to cause side effects than ACAM2000.

If you’re at risk of mpox, ask a healthcare professional about the risks and benefits of vaccination.

If you were born before 1972, you might have received the smallpox vaccine. Protection against smallpox lasts around 3 to 5 years, according to the Centers for Disease Control and Prevention (CDC).

It’s not clear how much protection a previous smallpox vaccine offers against mpox in the context of the current outbreak. In general, childhood vaccinations are not likely to provide lifelong protection, with effectiveness decreasing over time.

The 2022 review cited above indicates that although people who received the smallpox vaccine as children can still contract mpox, they may be less likely to experience severe symptoms than unvaccinated individuals.

But this may not be true for everyone who received the smallpox vaccine as a child. The authors of a 2020 study that included women who received the smallpox vaccine as children found that subsequent HIV infection decreased smallpox immunity later in life.

Protection against mpox is highest 2 weeks after the second dose of the smallpox vaccine. It’s not clear how long protection lasts, with research currently in progress.

The vaccine is effective both before and after exposure to mpox. It’s most effective if you get it within 4 days of exposure. If you get it within 2 weeks of exposure, it can still reduce the severity of symptoms.

The JYNNEOS vaccine has been FDA approved for the prevention of mpox since 2019.

You need two doses of the vaccine for adequate protection against mpox. You’ll receive the second dose 1 month after the first dose. JYNNEOS is most effective around 2 weeks after the second dose.

Who’s at risk of monkeypox?

Anyone exposed to the virus can get mpox. In the current outbreak, men who have sex with men have the highest risk of contracting it.

You contract mpox through close contact with someone who has it. This can include activities such as:

  • touching, hugging, and kissing
  • oral, anal, or vaginal sex
  • prolonged face-to-face contact

The risk of contracting mpox from touching objects or surfaces touched by someone with mpox is low.

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The CDC recommends avoiding close or intimate contact with someone who has a confirmed case of mpox or an mpox rash.

Try to also avoid sharing utensils or handling objects that belong to someone who has mpox. Finally, wash your hands often.

It’s best to take the same precautions against mpox whether you receive the vaccine or not.

Mpox is a virus that causes a skin rash, fever, chills, and other symptoms. It’s similar to smallpox but tends to be milder.

Because smallpox and mpox share similar characteristics, smallpox vaccines can also protect against mpox. The FDA currently recommends them for people exposed to mpox or at risk of future exposure.