Are there vaccines against mpox? How effective are they?

Mpox has gained worldwide attention since it was declared a global health emergency by the World Health Organisation (WHO) last week. A new and possibly more transmissible strain – Clade 1b – of the disease has been spreading in the Democratic Republic of Congo (DRC).

The viral infection, formerly known as monkeypox, has been reported in five African countries, Sweden, Pakistan and the Philippines this year. As the surging cases trigger a cause of concern globally, there are questions among the COVID-weary populations about vaccines to protect against the disease.

Let’s take a closer look.

What is mpox?

Mpox is a viral infection caused by the monkeypox virus, which belongs to a genus of viruses called Orthopoxvirus.

The Orthopoxvirus family consists of the variola virus, which causes smallpox, the cowpox virus, and the vaccinia virus.

The common symptoms of mpox include skin lesions, fever, headache, muscle and back pain, low energy, and swollen lymph nodes.

The disease spreads through physical contact with an infected person, materials or animals.

The WHO sounded its highest level of alert for mpox last week, noting the 14,000 cases and 524 deaths have been reported in Africa this year.

The United Nations health agency last declared mpox a global health emergency in 2022 when a milder strain called Clade 2 caused the outbreak.

Is there a vaccine for mpox?

There are vaccines against mpox but no specific ones that target the monkeypox virus.

As viruses from the Orthopoxvirus genus are genetically similar, the vaccines developed to protect from other viruses can be used for mpox, too, reported DW.

Speaking to India Today, Dr Rajeev Jayadevan, infectious diseases expert and member of IMA Kochi, said, “There is no vaccine created specifically for the mpox virus. When the global mpox outbreak occurred in 2022, we were hoping that the smallpox vaccine could cross-protect against mpox.”

Vaccines protecting against mpox follow cross-reactivity. For example, there are viruses M, V and C from the Orthopoxvirus genus which are structurally similar. A vaccine that protects against virus C will also be able to tackle viruses M and V.

Antibodies produced by someone infected by the variola virus will also keep them safe against a mpox infection.

The European Centre for Disease Prevention and Control (ECDC) has recommended travellers get vaccinated against mpox if they are visiting affected areas in Africa.

Which vaccines are there?

Currently, there are a few vaccines against mpox , including Jynneos (MVA-BN) and Acam2000.

The MVA-BN vaccine, or the Modified Vaccinia Ankara-Bavarian Nordic, has been approved by the United Kingdom, the United States, the European Union/European Economic Area (EEA), Switzerland and Canada.

Developed around the 1950s, the Modified Vaccinia Ankara vaccine was used to protect against smallpox. Its current form, MVA-BN, is reportedly marketed as Jynneos, Imvamune and Imvanex.

The US Food and Drugs Administration (FDA) has green-lit ACAM2000 for protection against smallpox and mpox.

In 2022, Japan gave a nod to the smallpox vaccine LC16 for use against mpox. Russia licensed OrthopoxVac the same year for vaccination against smallpox, mpox and other Orthopoxviruses.

A new mRNA vaccine — BNT166 — is being developed to particularly target antigens on the monkeypox virus, reported DW. 

Are these vaccines effective?

Yes. According to the WHO, vaccination can help in preventing mpox.

The US Centers for Disease Control and Prevention (CDC) suggests getting two doses of the vaccine for “maximum” protection against mpox.

Previous research has shown that the smallpox vaccine is about 85 per cent effective against mpox. However, people who have got a smallpox jab seem to contract milder cases of mpox, reported DW.

“Regarding the vaccines for mpox, smallpox vaccines do provide significant protection due to the close genetic relationship between the two viruses. Two vaccines are currently used. The smallpox vaccine (vaccinia virus vaccine) has been shown to offer cross-protection against mpox due to the genetic similarities between the two viruses. This vaccine was originally developed to eradicate smallpox, and since the two viruses belong to the same family, the immunity provided by the smallpox vaccine can indeed reduce the severity of mpox or prevent it altogether,” Dr Giridhar Babu, epidemiologist, physician scientist, author on global health and infectious diseases, told India Today.

The antiviral drug tecovirimat, also known as TPOXX, is also commonly used to treat mpox. However, the US National Institutes of Health (NIH) said last week that the medicine did not speed up healing for people in a clinical trial in DRC infected with the new strain of mpox.

With inputs from agencies