Vaccino contro il tifo

You should be immunised against typhoid before you travel to certain parts of the world where the risk of typhoid is high - in particular, countries in the Indian subcontinent and the Middle East. There are two typhoid vaccines available in the UK - an oral and an injectable vaccine.

Why get the typhoid vaccine?

The typhoid vaccine provides immunisation against typhoid fever. Typhoid fever is caused by a germ (bacterium) called Salmonella typhi (S. typhi). This bacterium may contaminate food or drinking water in areas of poor sanitation. Typhoid ranges from being a mild illness to a fatal one. Symptoms include sudden onset of:

• Alta temperatura (febbre).

• Forte mal di testa.

• Sensazione di malessere (nausea).

• Dolore addominale.

• Perdita di appetito.

• Costipazione oppure diarrea.

These symptoms can be very severe.

(Nota: there are many types of salmonella bacteria which can infect people. Most remain in the gut and cause diarrhoea. S. typhi is more invasive - it can get from the gut into other parts of the body and it causes the more serious illness of typhoid fever.)

Travellers to areas where typhoid is a problem should be immunised, particularly where hygiene and sanitation are poor. The worst affected areas are Asia, Africa and Central and South America, so you should be immunised if visiting these countries, especially if you are visiting friends and relatives.

Vaccination may not be needed for short stays if you stay in good accommodation (including most package holidays). Your GP or practice nurse can advise if you should be immunised against typhoid for your travel destination.

People who handle specimens which may contain typhoid bacteria should also be immunised.

There are two typhoid fever vaccines available in the UK - an oral vaccine and an injectable vaccine. Both vaccines stimulate your body to make antibodies against typhoid germs (bacteria). These antibodies protect you from illness should you become infected with typhoid bacteria. It is important to remember that not everyone who is vaccinated will be totally protected against typhoid fever. No vaccine is 100% effective and the oral typhoid vaccination is somewhat less effective than the injectable one.

The oral vaccine

The oral vaccine is given as three capsules, one taken every other day. The capsules should be kept refrigerated. Each capsule should be taken with cold or lukewarm liquid (no warmer than 37°C), approximately one hour before a meal. It should be swallowed whole as soon as possible after being placed in the mouth, and not chewed.

The oral vaccine should be completed one week before you travel, as protection takes at least seven days to begin. This oral vaccine should only be given to children over 5 years of age. Antibiotics and some malaria tablets can stop the oral vaccine working. Most malaria tablets should not be taken for at least three days after receiving the oral vaccine. Your nurse will be able to advise you further about this.

The injectable vaccine

The injectable vaccine is given as a single injection into your upper arm or thigh. It should be given at least two weeks before you travel, ideally one month before.

Re-vaccination is needed eventually as the protective effect of the vaccines fades over time. A booster dose is recommended every three years for the injectable or the oral vaccine if you are still at risk - eg, due to still travelling to high-risk areas. It is important to keep a record of which vaccinations you have, and when and where you have them.

A combined vaccine against typhoid fever and hepatitis A is also available. This may be useful if you require protection against both illnesses. The hepatitis A component gives protection for one year and the typhoid component gives protection for three years.

Mild local soreness and redness may occur after the injection for a few days. High temperature (fever) can occur in about 1 in 100 people. Following oral vaccine, the most common side effects are feeling sick (nausea), diarrhoea, fever and headache. Serious reactions are very rare for both vaccines.

Very few people cannot be given the injectable typhoid vaccine. It should not be given to:

• People with an illness with high temperature (fever). It is best to wait until the illness has subsided before being immunised.

• People who have had a severe (anaphylactic) reaction to the vaccine in the past.

• Young children - when children are too young to be vaccinated, very careful attention to food and water hygiene is essential if taking children to an at-risk area.

There are currently no data on the safety of these vaccines in pregnant or breast-feeding women. However, if the risk of typhoid is high then you may be advised to have the vaccine if you are breast-feeding or pregnant.

There are some additional restrictions that apply differently to the oral vaccine and to the injectable vaccine.

The oral vaccine should not be given to:

• People who have had an allergy to gelatin.

• Children under the age of 6 years.

• People who have reduced immunity (people with test HIV, those taking high-dose long-term steroids, those receiving chemotherapy, etc).

The injectable vaccine should not be given to:

• Children under 2 years of age, as it is not licensed for them. This means that the manufacturer cannot offer guarantees about its effects or effectiveness in that age group.

• Children under the age of 2 years, who may not acquire the same level of immunity from the vaccine, due to the immaturity of their immune systems.

Nota: doctors may occasionally recommend injectable vaccine use in children aged 12-24 months if the risk of typhoid is very high.

People with typhoid fever pass out the bacteria with their stools (faeces), and sometimes in their urine. Even when symptoms have gone, about 1 in 10 people who have had typhoid fever remain carriers for some time. This means that some bacteria continue to live inside the gut and you continue to pass out bacteria with your stools.

If hygiene is not good then the bacteria can be passed to others who may then get typhoid fever. About half of carriers become free of the typhoid bacteria within three months. However, others continue to pass out typhoid bacteria with their stools long-term.

Periodo di incubazione

The incubation period for the disease is usually 1-3 weeks. This means that you do not get symptoms for 1-3 weeks after becoming infected. Around 200 cases are notified in the UK each year. About 8 in 10 of these cases are in people who caught the infection abroad, and most of these were visiting friends or relatives in South Asia. Typhoid infection can be successfully treated with antibiotic medicines, which reduce the chances of serious illness.

Remember - vaccination for travellers is only one to prevent typhoid fever. Both typhoid vaccines are only about 75% effective, particularly if you are exposed to large numbers of typhoid germs (bacteria).

Safety in pregnancy is not known but there is no reason to believe the vaccine risks harm to the mother or baby, so it is used if travel is essential and the risk of typhoid is high.

So, when you travel to high-risk areas you should:

• Have good personal hygiene.

• Only drink water or other drinks that are known to be safe (bottled water, sterilised water, etc).

• Only eat foods that have been cleaned and/or prepared properly.

La Dott.ssa Mary Lowth è un'autrice o l'autrice originale di questo opuscolo.