China has now vaccinated nearly 3.8 million people against the potentially fatal H1N1 influenza virus.
"Given the estimated 390 million people nationwide who are considered at high risk of the disease, the vaccine supply is limited," Liang Wannian, deputy director of the emergency response office of the Ministry of Health, said yesterday.
The top drug authority has so far approved nearly 52.9 million doses of the vaccine produced by eight domestic manufacturers. The ministry plans to inoculate 65 million people by the year's end.
As the pandemic peaked in the country with sharply increasing total cases and fatalities, the mass inoculation program is scaling up across the nation, first at key areas relatively hit harder by the virus and among the priority groups including the young, seniors and those serving key posts in public service.
"The peak of the H1N1 pandemic will last until next March in China, with constantly and rapidly increasing infections and deaths," Liang said.
"If possible, people should get the H1N1 vaccination, which is free and voluntary, as early as possible," he said.
He added the vaccine had proven to be safe and effective and most of the adverse reactions reported so far from the jab had been mild and temporary.
Liang's warning came one day after Premier Wen Jiabao called for tightened measures against H1N1 influenza as the country is facing a "grim situation".
In a visit to a children's hospital in Beijing, Wen said the country faces severe challenges in the prevention and control of H1N1 and some areas are likely to have a sharp increase in the number of patients infected by the epidemic.
Wen warned the country faced an "extremely grim" job in preventing the spread of the flu strain, calling on more people to be vaccinated on a voluntary basis and for vaccine production to be raised.
People must be "encouraged to get vaccinated as soon as possible" and "research into and production of vaccines must be stepped up", he added.
Television pictures showed Wen, a mask tied over his face, talking to children, parents and workers at the hospital.
Medical staff should be careful and avoid infection when treating patients, he said.
China has reported almost 45,000 infections, including six deaths, the latest of which was on Saturday in the northeastern province of Heilongjiang.
According to an official in charge of publicity in the Heilongjiang provincial health department who declined to be named, the patient was a local adult of the capital Harbin.
Xinhua News Agency added that a cold snap bearing down on northern China could heighten the flu risk.
But Wen also struck a note of optimism. He said the country is fully confident and capable of preventing outbreaks.
"We must work as hard as possible to reduce the number of serious cases and deaths," he said.