Adults and children in the Asian financial hub, which retains some of the world's toughest Covid precautions, are required to have at least three coronavirus vaccine shots.

"Recently a series of young children have been infected with the new coronavirus. The situation of severe illness and even death is of great concern," the government said in a statement announcing the reduction in age.

The government said it was also negotiating with China's Fosun, which supplies Germany's BioNtech vaccine, to purchase a formula of that vaccine for children.

The minimum age to get a shot of the BioNtech vaccine is five.

About 90 percent of Hong Kong's more than 7 million people have had two doses of a coronavirus vaccine and about 67 percent have had three.

Residents can choose between China's Sinovac and BioNtech.

A government advisory panel on Monday recommended that a fourth vaccine dose be given to those over 50.

The Chinese-ruled city has reported more than 1.3 million Covid cases and 9,500 deaths since the pandemic started, most of which occurred this February and March due to the fast-spreading Omicron variant.