The UK Foreign Office has a very good website with plenty of useful advice on travelling abroad and it also offers up to date information on the safety & security situation in each country.
It is therefore a good idea to get up to speed with your chosen destination/s by visiting the FCO website before you set off: https://travelaware.campaign.gov.uk/
You may also wish to follow the FCO on Twitter so as to get updates whilst you are abroad @FCOtravel. This service aims to help travellers have a trouble free trip by providing advice and information before, and during, their trip abroad. It will also provide assistance in the case of an emergency.
For up to date travel advice in Vietnam please visit: https://www.gov.uk/foreign-travel-advice/vietnam