"We appreciate your understanding as we continue to operate in a safe and secure manner for our customers and staff," the embassy wrote on Facebook.
Visa application centers in Ho Chi Minh City and Da Nang remain open.
The U.K. visa application center in Hanoi resumed operation on Aug. 30 last year after prolonged closure due to strict social distancing measures.
Hanoi has topped the nation's daily infection tally for over a month, with cases climbing to nearly 7,000 a day. It has recorded over 210,000 cases and 864 deaths during the fourth coronavirus wave that hit the country in April last year.
Vietnam has resumed commercial flights to 20 of 28 countries and territories that it operated direct flights to before the pandemic, including the U.K.