'Stealth' Omicron sublineage also dominant in Hanoi

Vu Cao Cuong, deputy director of the Hanoi Department of Health, on Thursday said among 109 coronavirus samples taken from Dec. 4 last year to Mar. 1, 93 of them were Omicron (80 percent). Among the Omicron samples, 86 belonged to the BA.2 sublineage, dubbed a "stealth" sublineage because while it still registers as positive on a PCR test, it is not immediately discernible as Omicron due to the lack of a particular gene.

The BA.2 sublineage is also around 1.5 times more contagious than the original Omicron strain (BA.1) and may evade immune responses triggered by vaccines better than the original.

In Ho Chi Minh City, the "stealth" Omicron sublineage is also the currently dominant strain.

Tran Thi Nhi Ha, director of the Hanoi health department, said the BA.2 sublineage is spreading quickly, but the number of hospitalized, severe Covid-19 cases has been dropping in the last few days.

"The percentage of Covid-19 cases being hospitalized is only 1-1.5 percent," she said.

Hanoi has recorded over 520,000 Covid-19 cases in the fourth coronavirus wave. Within the past two weeks, the number of cases has jumped by 343 percent, with peak periods recording around 32,650 cases in a single day.

Around 95 percent of cases in the capital are either mild or asymptomatic, with a death rate at 0.4 percent.