Yellow fever vaccine

A shot helps keep you safe.

It stops a bad sickness. This sickness is in Africa and South America. The shot uses a weak germ to help you. It helps your body stay strong.

Most people stay safe for their whole life. You may get the shot when you are a baby. It is good for people who travel to far lands. This shot is a great way to stay well.

A yellow fever vaccine helps keep you safe. Yellow fever is a viral infection. It is common in Africa and South America.

The vaccine is made from a weakened virus. This means the germ is too weak to cause the disease. It is given by an injection into a muscle or under the skin. Most people become immune within ten days. They are 99% protected within one month. This protection often lasts a lifetime. Most people do not need another dose later.

Doctors say the vaccine is generally safe. Some people might get a headache or a fever. Very few people have serious problems.

Many people use the vaccine to stay well. The World Health Organization recommends it for babies. They suggest it between nine and twelve months of age. People traveling to risk areas should get it too. Some countries ask for a certificate to prove you had the shot. This helps stop outbreaks of the disease.

The yellow fever vaccine is a way to stay safe from a viral infection. This disease is common in parts of Africa and South America.

The vaccine is very important for stopping outbreaks of the sickness. It is on the World Health Organization's List of Essential Medicines. Most people get protection within ten days of the shot. They are 99% protected after just one month. This protection seems to last for a person's whole life.

This vaccine works by using a weakened version of the virus. Scientists call this an attenuated virus. It is strong enough to teach the body how to fight, but too weak to cause the disease. The vaccine is given as an injection into a muscle or under the skin. Most people find it safe, though some might have a mild fever or a headache. Very few people have serious reactions. For example, severe allergies happen in about eight per million doses.

Finding the right vaccine took many years of hard work. In the early 1900s, scientists like Hideyo Noguchi tried to make one. He thought the disease was caused by a bacterium, but he was wrong. Later, researchers used human serum to make a vaccine. This worked, but it was hard to make enough for everyone. In 1937, Max Theiler discovered a much better way. He found a special version of the virus called 17D. This discovery helped him win the Nobel Prize in 1951.

Today, the 17D vaccine is the only one used around the world. It is grown using chicken eggs to help the virus multiply. More than 400 million doses of this vaccine have been given. Since the 1930s, only 12 cases of yellow fever have happened after 600 million doses. These few cases all happened within five years of the shot. This shows that the vaccine stays strong as time goes by. Even though it is old, it is still very effective.

Many people use the vaccine when they travel to new places. Some countries even require a certificate to prove you had the shot.

The World Health Organization says babies should get it between nine and twelve months old. People traveling to places where the disease is common should get it too. You should get the shot ten days before you travel. This gives your body enough time to build up its defenses. It is a simple way to stay healthy while exploring the world.

The yellow fever vaccine is a medical tool used to prevent a viral infection called yellow fever. This disease occurs primarily in tropical regions of Africa and South America.

Because the virus can cause serious illness, the vaccine is included on the World Health Organization's List of Essential Medicines. It is used globally to control outbreaks and protect people living in or traveling to endemic areas. Most people develop immunity within ten days of receiving the shot. Within one month, they are 99% protected. This protection appears to be lifelong for most individuals.

The vaccine works by using an attenuated virus. An attenuated virus is a version of the virus that has been weakened in a laboratory. It is still alive, but it is not strong enough to cause the actual disease in a healthy person. Instead, it teaches the immune system to recognize and fight the virus. The current version, known as the 17D vaccine, is grown using chicken eggs to help the virus multiply. The vaccine is administered as an injection into a muscle or just under the skin.

While the vaccine is generally safe, it is not suitable for everyone. It is contraindicated, or medically advised against, for certain groups. This includes infants between zero and six months old. It should also not be given to people with primary immunodeficiencies or thymus disorders. These conditions affect how the body's immune cells function. People taking immunosuppressant drugs should also avoid the vaccine. However, it is considered safe for people with HIV infection if they do not have active symptoms. It is also considered safe for use during pregnancy for those at risk of exposure.

Most side effects are mild, such as a headache, muscle pains, or a fever. However, more serious reactions can occur in very rare cases. Severe allergic reactions happen in about eight per million doses. Serious neurological problems occur in about four per million doses. Organ failure occurs in about three per million doses. There are also two specific rare conditions: YEL-AVD and YEL-AND. YEL-AVD, or yellow fever vaccine-associated acute viscerotropic disease, causes a severe illness that looks like the actual disease. YEL-AND is a neurotropic reaction involving the nervous system. Many adverse reactions are actually caused by allergies to the eggs used to grow the virus.

The history of the vaccine is a long journey of trial and error. In the early 20th century, Hideyo Noguchi mistakenly believed the disease was caused by a bacterium. Later, scientists used human serum to create vaccines, but this was difficult to produce in large amounts. In 1937, Max Theiler, working with Hugh Smith and Eugen Haagen, discovered a breakthrough. They found a mutation in the virus that created a highly effective, weakened strain called 17D. This discovery earned Theiler the Nobel Prize in Physiology or Medicine in 1951. Since the 1930s, only 12 known cases of yellow fever have occurred after 600 million doses were given.

Global supply and demand for the vaccine are managed by organizations like the WHO and Gavi. In the mid-2000s, the WHO Yellow Fever Initiative was launched to address rising cases in Africa and South America. As of 2013, there were four WHO-qualified manufacturers in Brazil, Senegal, Russia, and France. Demand has grown significantly, with projections reaching 62 million doses per year by 2014. However, in 2013, UNICEF reported that supplies were insufficient to meet this need. Manufacturers were producing about 35 million of the 64 million doses required annually.

Vaccination is a key part of a larger strategy to manage the disease. Medical experts recommend using insecticides, protective clothing, and house screening to control mosquitoes. However, these methods are not always enough. People in endemic areas are encouraged to use personal insecticide spray. For travelers, timing is critical. They should receive the vaccine at least ten days before entering an endemic area. This ensures the body has enough time to build full immunity. Some countries even require a vaccination certificate for entry to prevent the spread of the virus.