Lam said the drug is in high demand as the SAR has just entered a seasonal influenza peak, which typically ends in April, but was delayed as the mask mandate was only lifted last month.

Speaking on radio yesterday, Lam said the world is experiencing influenza outbreaks on a global scale.

The manufacturers of Tamiflu, which contains the antiviral medication Oseltamivir, need time to cope with the sudden surge in demand, he said. "We haven't seen seasonal influenza outbreaks over the past three years so many doctors do not have a lot of flu medicine in stock. Doctors have checked with pharmaceutical companies, but they could only get a small amount of the medicine, or none at all."

He said some doctors in the territory who reported limited stocks of liquid Tamiflu had to use the drug's capsule version for adults to cook up liquid medicine for children.

The Department of Health has earlier said it has stored 11 million doses of antiviral drugs, of which 90 percent are Oseltamivir.

Lam said that private clinics facing shortage of the drug should correspond with health authorities and added that the authorities have been in contact with the manufacturers to ensure sufficient supply.

Roche, the Swiss manufacturer of the drug, has promised to ship extra supplies and an urgent delivery has already been scheduled for the end of next month.

President of the Society of Hospital Pharmacists William Chui Chun-ming said not all patients catching the flu need to take Tamiflu, as he called for people to leave the drugs to those in urgent need.

"There is a shortage of Tamiflu in liquid form because it can only be kept for two years. Although we have an adequate supply of the drug amid the pandemic, many of them have expired now after three years," Chui said. "People should understand that not all of them have to take Tamiflu after catching the flu, and only high-risk groups and young children have to take the medicine."

The supply of flu vaccine has resumed and parents need to make appointment few days in advance, Lam assured.

So far, only around 10 percent of elderly citizens have received the flu vaccine, and the vaccination rate among children is lower than 10 percent, Lam said, adding that to develop herd immunity the vaccination rate must reach 60 to 70 percent.

Meanwhile, the average waiting time for accident and emergency ward of at least four public hospitals - Kwong Wah Hospital, North District Hospital, Prince of Wales Hospital and Tin Shui Wai Hospital - was as much as eight hours yesterday morning.

The situation improved in the afternoon, but patients at Tin Shui Wai Hospital and Princess Margaret Hospital had to wait seven and six hours respectively.