The passive voice is rarely used in Vietnamese language. As I know, the passive voice in Vietnamese is rarer than in most European languages. Use of passive voice in Vietnamese is rare not because Vietnamese speakers avoid the use of passive form nor because teachers teach them that it is not desirable but it seems to be a natural characteristic of Vietnamese expression.
The English passive voice is many times rendered in Vietnamese by use of the word "do" (which is pronounced something like /io/) and means "through the agency of". The Vietnamese word "do" stands right before the perpetrator of the verb’s action.
Quyển sách này do ông Nguyen Van Vinh viết (lit. classifier – book – this – through the agency of – grandfather – Nguyen Van Vinh – write) = This book was written by Mr. Nguyen Van Vinh.
I have met very few Vietnamese who were able to use correctly the passive voice in English. Usually, they avoid the use of passive voice and I found impossible to convince them that English passives entail no special difficulties. Vietnamese learners of English always associate Vietnamese "do" with the English word "by", which they are, in consequence, liable to misuse.