Their are loads of websites about the health risks of visiting other countries, but there's only one OFFICIAL site (funded by the Foreign & Commonwealth Office).
Quote from that site:
"Travellers should practice strict food, water and personal hygiene precautions even if vaccinated.
Most travellers are at low risk and do not need vaccination".
Source:
http://www.nathnac.or...s/country_page_DO.htm
It's worth noting (from the information on that site) that vaccination is only 50% to 80% effective against one type of typhoid and totally ineffective against another. So practising good food hygiene (rather than vaccination) really is the key to avoiding infection.
Chris