PHNOM PENH, Cambodia (AP) — Cambodia began vaccinating 3- and 4-year-olds with Chinese-made Sinovac shots Wednesday after finding young children accounting for many new infections.

Prime Minister Hun Sen appealed for parents to get their children vaccinated as soon as they can and said five of his 21 grandchildren and one of his daughters have tested positive for the omicron variant of the coronavirus.

“To overcome COVID-19 depends not just on the government or the Health Ministry, but needs the participation of all the people,” Hun Sen said at a groundbreaking ceremony for a wastewater treatment facility on the outskirts of the capital Phnom Penh.

He had endorsed the vaccination plan for the younger children last week after health officials found at least 25% of newly reported infections involved children under 5.

After vaccinating adults and older children, Cambodia approved shots for ages 6-11 in September last year as part of reopening its schools. In November, vaccinations for 5-year-olds were approved.

More than 80% of Cambodia’s almost 17 million people have received at least two shots. China’s Sinovac and Sinopharm vaccines account for most inoculations.

A recent sharp rise in the number of cases had driven some residents in Phnom Penh to stock antiviral medication to treat their illness or prepare for the possibility of catching the virus.

They have been purchasing Molnupiravir — a pill developed by the pharmaceutical company Merck — which was authorized by the Health Ministry last November for home-based treatment of mild to moderate cases. Cambodia has purchased 4 million pills, suitable for treating 10,000 people.

Cambodia’s Health Ministry on Wednesday reported 558 new COVID-19 cases and one related death, bringing the nation’s totals since the pandemic began to 128,133 cases and 3,023 deaths.