If I got the smallpox vaccine as a kid, am I protected against monkeypox?

Infectious Diseases Vaccines

Short answer: Probably to some degree, but just how much is up in the air.

Because the virus that causes monkeypox is similar to the smallpox virus, smallpox vaccines are effective at preventing people from getting monkeypox. Prior studies using the Dryvax vaccine (the first-generation smallpox vaccine that was used during smallpox eradication), showed that smallpox vaccine is about 85% effective at preventing monkeypox. Good news!

Why don’t we know how much protection someone has if they got the vaccine as a kid?

Because smallpox was eradicated! The US stopped giving the smallpox vaccine routinely in 1972 and the last naturally occurring case of smallpox in the world was in 1977. We know that immunity from the smallpox vaccine can wane over time, but just how much is unclear. There are antibody studies, some of which show waning after about 5-10 years, but antibodies do not tell the whole picture of immunity and protection against a disease and its complications. Without any more disease or new cases, it was not possible to correlate antibody levels with disease susceptibility. Before eradication, the World Health Organization recommended revaccination every 3-10 years depending on the circumstance.

In this current outbreak, some people who had received smallpox vaccination as a child did catch monkeypox. In a study in Spain, for example, 32 of the 181 patients with monkeypox had received childhood smallpox vaccine. Other factors, like HIV and other immunocompromising conditions, may increase waning over time. It is too early in the outbreak to tell how much protection one gets from smallpox childhood vaccination against monkeypox.

It is certainly possible that smallpox vaccination more than 40 years ago offers some protection against monkeypox, but it is not a good idea to bank on it! If you are eligible for a vaccine and one is available to you, go for it. There are two vaccines currently available under emergency use authorization for monkeypox: JYNNEOS and ACAM2000.
Unfortunately, there are limited supplies of the vaccines and only some people are eligible. This includes:

➡People who have had contact with someone who has monkeypox

➡People who are aware that one of their sexual partners in the past 2 weeks has been diagnosed with monkeypox

➡People who have had multiple sexual partners in the past 2 weeks in an area when monkeypox transmission is occurring

➡People whose jobs expose them to monkeypox

As supply increases, it is expected that more folks will become eligible for vaccination. Talk with your healthcare provider if you have questions about the vaccines and eligibility.

Stay safe. Stay well.
Those Nerdy Girls


CDC Monkeypox and Smallpox Vaccine Guidance

WHO Monkeypox Outbreak 2022

ACAM2000 Vaccine


Smallpox Vaccine Basics

History of Smallpox

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