'Stealth' Omicron sublineage dominant in HCMC: health department

Among 67 coronavirus samples sequenced in HCMC, 24 belonged to the BA.1 sublineage and 43 to the BA.2 sublineage, also known as the "stealth variant", said Tang Chi Thuong, director of the HCMC Department of Health. It is also the first time the stealth version of Omicron has been detected in Vietnam, he added.

"HCMC now has both Omicron sublineages, but the BA.2 one has proven dominant. It explains why the coronavirus is spreading so quickly," Thuong said.

The BA.2 sublineage is dubbed the "stealth variant" 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.

Citing the WHO, Thuong said current Covid-19 vaccines can still provide protection against the sublineage but would not be enough to make someone impervious to infection. As such, vaccinations must continue, he added.

Global studies state while the BA.2 sublineage doesn't cause more severe symptoms than the BA.1, it is more transmissible.

HCMC has recorded over 554,500 Covid-19 cases in the fourth coronavirus wave since late April.

Within a week from March 1 to 7, the southern city has recorded around 37,500 cases at schools, doubling that from the previous week. The number is rising more rapidly among primary school grades compared to others.

Phan Van Mai, chairman of HCMC People's Committee, said experts predict it might experience another Covid-19 wave in future. Therefore, the local health department needs to analyze and evaluate current coronavirus situations to bring forth viable solutions.

Random screening in HCMC in mid-February revealed Omicron was already the dominant variant in the city at the time. Twenty out of 30 Hanoi districts have also detected the variant through sample screening.