The monkeypox virus is closely related to the virus that causes smallpox, which is why medical experts say the vaccine can help to protect people.
The head of the World Health Organization has said that the monkeypox outbreak is one of the major problems facing the world right now.
The outbreak of the virus which has seen 20 cases in the UK with more expected to be reported today. There have been around 80 cases in Europe, the United States, Australia, Canada and Israel. Read more about what the WHO chief had to say here.
The virus is usually found in central and west Africa and does not spread easily to people. The risk to the public is said to be low and it usually causes only mild illness in people.
In the UK, authorities have offered a smallpox vaccine to some healthcare workers and others who may have been exposed
The Centers for Disease Control and Prevention (CDC) in America says that past data from Africa suggests that the smallpox vaccine is at least 85% effective in preventing monkeypox.
Experts also believe that vaccination after a monkeypox exposure may help prevent the disease or make it less severe.
Vaccination after exposure to monkeypox virus is still possible. However, the sooner an exposed person gets the vaccine, the better.
CDC recommends that the vaccine be given within four days from the date of exposure in order to prevent onset of the disease. If given between four and 14 days after the date of exposure, vaccination may reduce the symptoms of disease, but may not prevent the disease.
It says: "For most people who have been exposed to monkeypox, the risks from monkeypox disease are greater than the risks from the smallpox or monkeypox vaccine."
Monkeypox causes fever, headache, muscle aches, backache, swollen lymph nodes, a general feeling of discomfort, exhaustion, and severe rash.
Studies of monkeypox in Central Africa, where cases often go untreated, showed that the disease killed 1–10% of people infected.
In contrast, most people who get the smallpox or monkeypox vaccine have only minor reactions, like mild fever, tiredness, swollen glands, and redness and itching at the place where the vaccine is given. However, these vaccines do have more serious risks, too.
Based on past experience, it is estimated that between one and two people out of every one million people vaccinated will die as a result of life-threatening complications from the vaccine.
Routine smallpox vaccination ended in in 1971 after it was successfully eradicated in the UK. The Vaccination Act 1853 had made it compulsory for all children born after 1 August 1853 to be vaccinated against smallpox during their first three months of life.
The chief reason for the end of smallpox vaccination was that it had ceased to be endemic in the United Kingdom since the 1930s.
