An adviser of the National Task Force against COVID-19 said the BA.4 Omicron sub-variant whose presence was reported by the Department of Health (DOH) on Saturday is ''highly transmissible and could affect vulnerable persons like those with illness or senior citizens.''

''This is the problem,'' said Ted Herbosa in an interview at dzBB Sunday.

In an advisory Saturday, the DOH said the BA.4 Omicron sub-variant was detected from a Filipino who flew in from the Middle East last May 4.

''His positive test result for the subvariant was from a specimen collected on May 8. He was asymptomatic,'' the DOH said.

DOH said the European Centre for Disease Prevention and Control ''sees Omicron BA.4 as a variant of concern.'' ''A variant of concern is seen to either spread faster of cause worse illness,'' it added.

The DOH said all local government units '' are strongly advised to proactively seek the unvaccinated and those eligibile for boosters and to make it convenient to get a jab.''

Herbosa said authorities will monitor if COVID-19 cases will increase in the next few days.

''Since BA.4 is quickly transmitted, hospital patients may increase. That is why we are watching out for this,'' he added.

Herbosa said although there are few cases in COVID centers, they have received reports '' of small increases daily.'' DMS