Yellow fever is a serious disease. You should be immunised against yellow fever before you travel to certain countries. 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 at least two weeks before you travel to see if you need this immunisation.
What is yellow fever?
Yellow fever is a serious disease caused by the yellow fever virus which is carried by mosquitoes and which infects humans and other primates (eg, monkeys). For some people it can cause a flu-like illness from which they recover completely. However, for other people it causes symptoms of fever, being sick (vomiting), yellowing of the skin and 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 bites from infected mosquitoes of 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.)
Yellow fever occurs in certain countries of Africa and South 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 immunisation offers high protection against yellow fever infection, taking steps to avoid being bitten is also an important part of avoiding the disease.
Who should be immunised against yellow fever?
- 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 immunisation:
- In some countries, immunisation is compulsory for all incoming visitors.
- In some countries, immunisation is compulsory for those who have travelled from a 'yellow fever' area or country.
- Your doctor or practice nurse can advise if you should be immunised for your travel destination and whether you need this certificate of immunisation.
- 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 immunisation for travellers is twofold:
- Firstly it is to protect you against 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.
The vaccine and where it can be obtained
You should have an injection of vaccine at least ten days before the date of travel 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.
Yellow fever vaccine can only be given at accredited centres. Many GP practices are accredited. If your local GP practice is not accredited you can find a list of the nearest available centres from the National Travel Health Centre and Network - NaTHNaC (see below). You will then be issued with a vaccination certificate which gives the date your vaccine will become effective.
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.
What are the side effects of yellow fever vaccine?
Severe reactions after a yellow fever vaccine are very rare but mild reactions can last for up to 14 days. These include feeling generally unwell, headache, muscle aches, joint pain, mild fever or soreness at the injection site. Always contact a doctor if you have any concerns.
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. It is sometimes given after the sixth month of pregnancy if there is a high risk of catching yellow fever.
- This vaccine may be given if you are breast-feeding and cannot avoid being at high risk of catching yellow fever.
- 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.
- If you have had a severe reaction to the yellow fever vaccine in the past.
- If you have a thymus disorder.
Further reading and references
Yellow fever; World Health Organization, May 2016
Hayes EB; Is it time for a new yellow fever vaccine? Vaccine. 2010 Nov 2928(51):8073-6. Epub 2010 Nov 3.
Yellow fever: the green book, chapter 35; Public Health England (April 2014)
Lifelong Immunity from single dose of yellow fever vaccine; World Health Organization Media Release, May 2013
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