Yellow fever vaccine

You may need an International Certificate of Vaccination to prove you have been immunised, as some countries will not allow you entry unless you can produce one. Check with your practice nurse several months before you travel to see if you need the yellow fever vaccine. You will only be able to get it from your GP if they are a designated yellow fever centre - if not then you will have to see a private travel clinic. Since 2020 there have been some shortages of this vaccine, so allow plenty of time before you travel to get it sorted out.

What is yellow fever?

Yellow fever is a serious disease caused by the yellow fever virus which is transmitted by infected mosquitoes and which infects humans and other primates (for example, monkeys).

For some people it can cause a flu-like illness from which they recover completely. However, for other people it causes symptoms of high temperature (fever), being sick (vomiting), yellowing of the skin or the whites of the eyes (jaundice) and bleeding. This is fatal in about 1 in 12 cases. There is no medicine that can destroy the virus, so treatment is to support the person medically whilst they fight the infection themself.

Yellow fever is passed to humans and other primates such as monkeys by mosquitoe bites from a type which tend to bite during daylight hours. (These are different to the type of mosquitoes which carry malaria, which tend to bite from dusk to dawn.)

What country requires the yellow fever vaccine?

Yellow fever occurs in certain countries of Africa and South and Central America. In the distant past it has been present in Europe and Asia but these parts of the world are currently free of yellow fever.

Yellow fever is not transmitted directly from person to person; the mosquito is needed to carry the infection from one human to another. Therefore, whilst vaccination offers high protection against yellow fever infection, taking steps to avoid being bitten is also an important part of avoiding the disease.

Who should have the yellow fever vaccine?

• Travellers over the age of 9 months to countries where yellow fever is a risk. Some countries require an International Certificate of Vaccination against yellow fever before they will let you into the country. Yellow fever is the only disease which routinely requires proof of vaccination:

  • In some countries, vaccination is compulsory for all incoming visitors.

  • In some countries, vaccination is compulsory for those who have travelled from a 'yellow fever' area or country.

  • Your doctor or practice nurse may be able to advise if you should be immunised for your travel destination and whether you need this certificate of vaccination. Not all practices have the resources to do this - if yours doesn't then you'll need to go to a private travel clinic.

• Workers who handle material that may be infected by the yellow fever virus - for example, laboratory workers.

• People who are resident in areas where yellow fever is present.

The purpose of vaccination for travellers is two-fold:

• Firstly it is to protect you from catching yellow fever.

• Secondly it is to protect local populations from catching yellow fever from you, leading to an epidemic. Some countries are theoretically in danger of epidemics, as they have the right mosquitoes to transmit the virus, and have the kinds of monkeys who could become infected and act as a store or reservoir for the virus. They therefore require visitors to be immunised.

Where can I get the yellow fever vaccine?

Yellow fever vaccine can only be given at accredited centres. Many GP practices (but not all) are accredited. If your local GP practice is not accredited you can find a list of the nearest available centres from NaTHNaC (see 'Further Reading and References', below). You will then be issued with a vaccination certificate which gives the date your vaccine will become effective.

How does the yellow fever vaccine work?

The vaccine stimulates your body to make antibodies against the yellow fever virus. These antibodies protect you from illness should you become infected with this virus. The yellow fever vaccine is a live vaccine which can be given at the same time as other vaccines.

When should you get the yellow fever vaccine?

You should have an injection of vaccine at least ten days before the date of travel to countries with yellow fever to allow immunity to develop.

A single dose of vaccine was previously considered to provide immunity for at least 10 years. In 2013 the World Health Organization (WHO) declared that a single injection can be considered to give lifelong immunity. The International Health Regulations have not yet been altered to reflect this and so the certificate is only valid for 10 years, after which a booster is needed.

Some countries now accept it as being valid for life, so it is important to check the regulations for the countries you are visiting. You can do this on the WHO or National Travel Health Network and Centre (NatHNaC) websites or at your GP surgery.

What are the side-effects of yellow fever vaccine?

Severe reactions after receiving the yellow fever vaccine are very rare but mild reactions can last for up to 14 days. Common side-effects of the vaccine may include feeling generally unwell, headaches, muscle aches, joint pain, mild fever or soreness at the injection site. Always contact a doctor if you have any concerns. A more serious, but rare, side-effect is encephalitis or infection in the brain. Most people recover fully from this side-effect which presents between 2 and 56 days after the vaccine with a fever or headache which may progress to confusion and a coma. This serious side-effect is more common in those aged over 60, who should therefore only have the vaccine if there is a serious and unavoidable risk of catching yellow fever.

Who should not receive the yellow fever vaccine?

The yellow fever vaccine is not usually given under the following circumstances, although advice should be taken from your doctor or practice nurse:

• If you have reduced immunity (immunosuppression) - for example, people with HIV, people taking high-dose long-term steroids, people receiving chemotherapy, etc.

• If you are ill with a fever you should ideally postpone the injection until you are better.

• As a rule, pregnant women should not be immunised with this vaccine, although if travel is unavoidable then the woman and her doctor will need to make an assessment of the risks versus the benefits of having the vaccine - a private travel specialist would need to be approached for this, rather than your GP.

• This vaccine may be given if you are breastfeeding and cannot avoid being at high risk of catching yellow fever, but expert advice should be sought before doing so.

• You should not have the yellow fever vaccine if you have had a severe (anaphylactic) reaction in the past to egg. (This is because the vaccine contains small amounts of egg. A severe reaction to egg is very rare and it does not mean an upset stomach eating eggs or disliking eggs.)

• Children under 9 months old should not receive the yellow fever vaccine. (Babies aged 6-9 months may occasionally receive the vaccine if the risk of yellow fever during travel is unavoidable.)

• Older travellers (those aged over 60 years) who have not previously been vaccinated against yellow fever are at a higher risk of side-effects with the yellow fever vaccine and should therefore only have it if there is a serious and unavoidable risk of catching yellow fever. .

• If you have had a severe reaction to the yellow fever vaccine in the past.

• If you have a thymus disorder.

Dr Mary Lowth is an author or the original author of this leaflet.