National Think B'Fore You Go Day aims to encourage families, gap year students and travellers to distant places to obtain the vaccination at least six months before they travel abroad.

"We've planned this campaign to coincide with the first burst of holiday advertising for 2007," said Alison Rogers, the chief executive of the trust.. "We think travellers should be looking after their health as well as their luggage when they go on holiday. Accidents do happen and you could find yourself in a high-risk situation without realising it."

The hepatitis B virus is found in blood and body fluids, and it is transmitted through sexual contact, contaminated medical or dental instruments and blood transfusions. Any contact through an open cut, sharing contaminated needles or unprotected sex can infect others. It is 100 times more infectious than HIV, and potentially fatal. The virus causes inflammation of the liver, making it more susceptible to life-threatening cirrhosis and liver cancer.

Rogers said: "A common misconception is that hepatitis B is only a danger for people who are sexually active. This is not the case. Imagine you are on holiday, and you or someone you are travelling with gets in an accident and winds up in the hospital. Having the proper vaccination before you go on holiday is like having health insurance."

Sporting activities such as skiing, cycling, horse riding and football put travellers at potential risk, according to medical research from the Journal of Travel Medicine.

Travel destinations where hepatitis B is most common include Eastern and Southern Europe, South-East Asia, South America, Africa, and the Middle and Far East.

"Travel agent members have a duty to raise the subject of vaccinations for far and away destinations at the time of booking," said Dee Byrne, a spokesperson for the Association of British Travel Agents. "However, with increasing numbers of holiday-makers opting for late bookings and venturing farther afield than in previous years, travellers need to ensure that the necessary vaccinations are taken and existing vaccinations are up to date."

The vaccination for hepatitis B is 95 per cent effective and available at local GP and specialist travel clinics.