Local hospitals in Vietnam are mostly public and heavily subsidized by the government. The low cost and quality treatment mean that they are running over capacity and some of them in quite bad conditions. You may end up catching another flu before being seen by a doctor.
In main cities, there are plenty of private clinics, including those that offer international quality medical care. You will have to pay double or triple the amount you would pay in public hospitals but for the sake of your health, it is worth the insurance’s money.
In rural area, medical care is scanty and you will have a hard time finding a decent clinics, let alone hospitals. Fortunately, there have been hardly any cases of tourists reported to be in critical condition while they are trekking on the mountain or visiting a rural community.
Take extra precaution when you travel, however, in each city’s pages there will be a list of suggested medical services. Take note of them, including their phone number and address should anything happen on the road and you don’t have access to the Internet.