Hoang Minh Trung, a 12th grader at the Lam Son High School for the Gifted in Thanh Hoa Province in central Vietnam, won the silver.
The bronze medal winners were 12th graders Duong Tung Lam from the central Nghe An Province, Hoang Thi Huyen Trang from the northern Phu Tho Province, and 11th grader Ha Vu Huyen Linh from Hanoi.
In both 2017 and 2018 Vietnam had won gold medals. In 2018 a Vietnamese contestant got the highest score in the entire competition.
The eight-day contest received over 285 contestants from 75 countries and territories.
Vietnamese students have been doing well at international contests recently.
A six-member Vietnamese team came seventh out of 110 teams at the International Mathematics Olympiad in the U.K. last week after winning two gold and four silver medals.
Five other students at the International Physics Olympiad bagged three golds and two silvers earlier this month.
A 2018 World Bank report said Vietnamese students are among the best academic performers in developing East Asia and the Asia-Pacific.