Fifteen people were hospitalized this week with swine flu, according to the National Hospital for Tropical Diseases in Hanoi.
These are the first swine flu patients to be recorded in the capital city in the past six months, Nguyen Hong Ha, vice director of the hospital, said Friday.
Only one of them showed symptoms of pneumonia, while others were admitted with mild ailments, he added.
Earlier this week, Ho Chi Minh City's Tropical Diseases Hospital reported the reemergence of the virus in the metro following a lull of several months.
Three women tested positive for the H1N1 virus.
Local health agencies have warned that the virus will affect more people from now until after Tet (Lunar New Year).
Swine flu was first detected in Vietnam in May, 2009.Since then, the Ministry of Health has logged more than 11,000 cases of the virus, including more than 50 deaths.
Officials say that the chances of an outbreak on the same scale seen in 2009 are very small.