Inoculations with Pfizer's bivalent COVID-19 vaccine targeting the omicron subvariants BA.4 and BA.5 is set to begin on Monday.

The introduction of the vaccine increases the types of available bivalent booster shots to three, with the administration of Moderna and Pfizer’s vaccines for the BA.1 variant already underway since last week.

All people aged 18 and older can receive those booster shots as long as they were either last vaccinated or infected with the virus at least 120 days ago.

With authorities confirming the onset of a new round of the pandemic in the nation, health officials are recommending booster shots particularly for those vulnerable to the disease including the elderly, those with underlying conditions and those at nursing facilities.

While the inoculation of the additional vaccine to be gradually given to those making reservations from October 27, same-day vaccinations will be also available from Monday with leftover doses.