Monkeypox: we have vaccines and drugs to treat it

Medicines are not normally needed to treat monkeypox. The disease is usually mild and most infected people recover without treatment within a few weeks. But there are vaccines that can be used to fight monkeypox outbreaks, which some countries are already using. And there are treatments for those who get quite sick from the virus.

Monkeypox belongs to the Orthopox virus genus of viruses, including smallpox. Fortunately, because of something called cross-protection, smallpox vaccines also work for monkeypox.

Although the world was declared smallpox-free in 1980, many countries keep stocks of smallpox vaccines for emergencies. For example, the smallpox vaccine is used to protect laboratory workers who accidentally come into contact with smallpox viruses (such as monkey pox or vaccinia – a smallpox virus similar to smallpox but less harmful). They are also kept in the event of a terrorist attacks who could use smallpox as a biological weapon

Vaccination against smallpox can go up to: 85% is effective at stopping monkeypox virus infection if given before people are exposed to the virus.

There are two types of smallpox vaccine. Both types are based on the vaccinia virus. An older type of smallpox vaccine contains the “live” vaccinia virus. The most important in this group are: ACAM2000which is approved in the US for protecting people from smallpox.

Although ACAM2000 cannot cause smallpox, the vaccinia virus it contains can replicate after the vaccine is administered, send from the vaccinated person to an unvaccinated person who comes into close contact with the injection site or leaking fluid for up to 21 days afterwards.

This also means that ACAM2000 is much side effects and should not be given to high-risk groups, such as pregnant or breastfeeding women, and people with weakened immune systems. People with weakened immune systems, including those with a hivcan get very sick from the vaccine.

The smallpox virus belongs to the same genus as monkey pox.
Phanie / Alamy Stock Photo

The other “live” vaccinia virus is the Aventis Pasteur Smallpox Vaccine† It has not been formally approved, but may be made available if other supplies run out.

A newer type of smallpox vaccine called Imvanex contains a live but modified form of the vaccinia virus called vaccinia Ankara. Imvanex, made by the Danish biotechnology company Bavarian Nordic, is licensed in the European Union for the prevention of smallpox.

In the US, the vaccine goes under the brand name Jynneos and is licensed to prevent both smallpox and monkeypox in adults at risk for these diseases. Jynneos has been used in the United Kingdom in previous cases of monkeypox.

Because Bavarian Nordic vaccines are made from a modified form of the vaccinia virus, they are considered safe for people in high-risk groups.

It usually takes between five and 21 days for someone who comes in close contact with an infected person to show symptoms from monkeypox (and most likely seven to 14 days), so it’s hard to say if giving the vaccine after someone has been exposed to monkeypox will fully protect them. However, the recommendation in the US and the UK is that, following a risk assessment, people exposed to the monkeypox virus will be offered a modified vaccinia Ankara vaccine dose as soon as possible, ideally within four days, but a maximum of 14 days thereafter.

Antivirals

In addition to vaccines, there are some medicines that could be used to treat monkey pox.

One such drug is tecovirimat which stops the spread of infection by interfering with a protein found on the surface of Orthopox viruses

Tecovirimat is approved in the US only for the treatment of smallpox. It has been tested in healthy people and has been shown to stop the smallpox virus in the lab. However, it has not been tested in people with smallpox or other Orthopox viruses† Yet in Europe tecovitimat is approved for the treatment of smallpox, monkeypox and cowpox under exceptional circumstances.

Another antiviral drug that could be used is cidofovir – an injectable drug that is licensed in the UK treat a serious viral eye infection in people with AIDS.

In the body, cidofovir is converted to the antiviral compound cidofovir diphosphate. Because cidofovir stops smallpox in the lab, it may be approved for emergency use in: smallpox or monkeypox outbreaks.

However, cidofovir is quite a potent drug and can injury the kidneys, so a better alternative could be the closely related drug brincidofovirwhat has been approved in the US for the treatment of smallpox.

Brincidofovir (brand name Tembexa) is given by mouth and can be prescribed to people of any age. The special design helps to get the right amount of the drug into the cells to release the cidofovir component and also makes it less harmful to the kidneys.

Brincidofovir is tested in humans for other viral conditions. The approval for use in smallpox in the US comes from: laboratory studies showing that it works against Orthopox viruses† For this reason, brincidofovir is also listed as a potential drug for the treatment of monkeypox

However, what we are still missing is data on how effective cidofovir, brincidofovir and tecovitimat will be in treating monkeypox infections in humans. A recent article, published in The Lancet Infectious Diseases examined the efficacy of brincidofovir (three patients) and tecovirimat (one patient) in monkeypox cases between 2018 and 2021 in the UK. The researchers reported poor efficacy of brincidofovir and called for more research on tecovirimat in human monkeypox infection.

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