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Smallpox and Mpox

What are they?

Smallpox is a serious, life-threatening disease caused by variola virus. Smallpox spreads through close contact with an infected person and can cause symptoms like headaches and fevers. In addition, it causes a rash over the whole body, which starts out as flat red spots that turn into blisters and then finally become scabs.


This disease was eradicated in 1980, meaning that no one has had smallpox since then. Before eradication, smallpox likely killed more people than all other infectious diseases combined. Because no one has gotten smallpox in more than 40 years, vaccination against it is no longer routine, but the US maintains a stockpile of smallpox vaccines in case of bioterrorism. Vaccination against smallpox may also be recommended for people who are at high risk of exposure to related viruses. 

Mpox (previously caused monkeypox) is caused by a virus that is closely related to smallpox. Mpox spreads through close contact with infected people or animals (or with contaminated materials). The symptoms of Mpox are very similar to smallpox symptoms. Because smallpox and Mpox are so closely related, smallpox vaccination can provide protection against Mpox. 

Vaccine Options:

What's the difference between them?

ACAM2000 is approved for any age to prevent smallpox. This vaccine is given in a unique way that involves putting a drop of the vaccine on the skin and inserting it into the skin with a two-pronged needle called a bifurcated needle. To learn more about how this vaccine is administered, click here.

Jynneos is approved for ages 18 and up to prevent smallpox and Mpox. Two doses of this vaccine are recommended for protection. Jynneos is given subcutaneously (in the fatty tissue under the skin) in the arm.

Smallpox Facts:

The first vaccine in history was given to protect against smallpox. The word vaccine comes from the latin word vacca, which means cow, because cowpox virus (vaccinia) was used to protect against smallpox.

In addition, smallpox was the first disease to be eradicated (only one other disease has been eradicated, which is called rinderpest, or cattle plague).

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