The storm made landfall in Quang Binh and Ha Tinh provinces at around 7 p.m., packing winds of more than 80 miles per hour, disaster officials said.
A 13-year-old boy drowned in Quang Ngai while trying to anchor his family's boat, and another death was reported in Quang Binh province, said provincial disaster official Truong Ngoc Hung.
Hundreds of houses collapsed and the typhoon tore the roofs off scores more, said Nguyen Duc Tien, a provincial disaster official.
The typhoon knocked down telephone and power lines in Ha Tinh Province, causing widespread blackouts.
Lekima, named after a Vietnamese fruit, destroyed thousands of hectares of rice crops in Nghe An Province, according to officials there.
As the storm approached Wednesday morning, disaster officials evacuated about 400,000 people from the region, moving them to schools and public buildings further inland.
Lekima was upgraded from a tropical storm to a typhoon as it approached the coast Wednesday afternoon.
Earlier, Lekima appeared to be heading toward southern China, where officials evacuated 100,000 people and called 20,000 fishing boats back to harbor.
It shifted course early Wednesday and began heading to Vietnam, which is prone to floods and storms that kill hundreds of people each year.