In 2022, during the first declared global health emergency for mpox, the European Union, United States, Canada, and other countries approved the use of the MVA-BN vaccine.

What Are Mpox Vaccines?

Vaccines that offer protection against mpox infection do exist, though no vaccines specifically target the monkeypox virus itself. How is this possible?

The monkeypox virus belongs to a group of viruses known as Orthopoxvirus, which are complex DNA viruses. This group also includes the variola virus (responsible for smallpox), the cowpox virus, and the vaccinia virus.

Due to the genetic similarities among these viruses, vaccines developed against one can also be used to protect against mpox.

How Do Mpox Vaccines Work?

The protection offered by mpox vaccines relies on a concept known as cross-reactivity. Cross-reactivity occurs when different antigens—like different virus species—appear similar to the immune system.

Because viruses in the Orthopoxvirus genus share structural similarities, antibodies produced against one virus, such as the variola virus, can also help protect against a monkeypox virus infection.

This cross-reactivity allows a vaccine developed for smallpox, for example, to also be effective against mpox infections.

Can I Avoid Mpox If I've Been Vaccinated Against Smallpox?

There is no guarantee of complete protection.

Smallpox was declared eradicated in 1980 following a global vaccination campaign. After the 1980s, mass immunization against smallpox ceased, which some researchers believe might have increased people's susceptibility to other Orthopoxvirus forms, including monkeypox.

People born after the end of the universal smallpox vaccination program generally have lower levels of antibodies against the monkeypox virus. This could explain why men aged 18-44 made up the majority of cases in the 2022-2023 mpox global outbreak.

However, prior smallpox vaccination doesn't mean someone is fully protected from mpox. Studies suggest that the smallpox vaccine is about 85% effective in preventing monkeypox virus infection, and those vaccinated for smallpox tend to experience milder mpox cases.

What Vaccines Are Currently Available?

As of August 2024, the MVA-BN vaccine (Modified Vaccinia Ankara-Bavarian Nordic) is the only one approved for use against mpox across the EU/EEA, UK, US, Switzerland, and Canada.

This vaccine uses a weakened strain of the vaccinia virus, part of the same Orthopoxvirus genus as the monkeypox virus. Originally developed in the 1950s and '60s in Germany to protect against smallpox, its current form, MVA-BN, was developed by the Danish biotech company Bavarian Nordic and has been in production since 2010. It is administered in two doses, typically 28 days apart.

The World Health Organization also lists two other vaccines approved by different regulatory bodies for mpox prevention. During the 2022 mpox outbreak, Japan approved the smallpox vaccine LC16, and Russia licensed OrthopoxVac for immunization against smallpox, mpox, and other orthopoxviruses. In the US and Australia, ACAM2000, a vaccine containing a live vaccinia virus, is recommended for people at risk of Orthopoxvirus exposure.

Are There Vaccines in Development?

Yes, one example is BNT166, a new mRNA vaccine specifically targeting monkeypox virus antigens, currently under clinical evaluation. You may be familiar with mRNA vaccines from the COVID-19 pandemic and the subsequent global vaccination efforts.

The World Health Organization continues to monitor and support the development of new vaccines for mpox.