Bird flu has mainly affected countries in East Asia
Japan is to become the first country in the world to vaccinate thousands of officials against bird flu.
Six thousand health workers and other staff will be inoculated over the next few months, and the programme might be extended to cover millions more.
Although bird flu has caused 240 deaths since 1993, none has been in Japan.
But there are fears that an outbreak elsewhere in Asia could spread quickly in Japan, which has some of the world's most densely-populated areas.
Bird flu is currently relatively difficult for humans to catch, but health authorities fear it could mutate into a form that is much more easily spread among humans, which could cause a pandemic.
Sensible or over-sensitive?
Japan has already stockpiled 20 million doses of so-called "pre-pandemic" bird flu vaccine for use after a major outbreak.
The vaccine has been made using the deadly H5N1 strain of the disease collected in Vietnam and Indonesia.
Japanese Health Minister Yoichi Masuzoe made the proposal for vaccination on Tuesday, and it was backed by a government-appointed panel of experts on Wednesday.
The plan is to initially use 6,400 doses of vaccine to inoculate doctors, quarantine inspectors and other health and immigration officials.
If successful, the government aims to expand the programme to others.
"If we obtain good results over its effectiveness and safety, we want to consider vaccinating (an additional) 10 million people who are in medical occupations" or other key jobs such as at utilities, Mr Masuzoe told reporters.
By taking this action, Japan is taking bird flu precautions to levels not seen anywhere else in the world, according to the BBC correspondent in Tokyo, Chris Hogg.
Japan is probably the only Asian country which has the resources to do this.
But is this sensible or an over-reaction to the threat posed by bird flu?
The World Health Organization does not sound convinced that it would improve the chances of Japan weathering a major bird flu outbreak, our correspondent says.
WHO spokesman Gregory Hartl told the Associated Press that the planned vaccinations were "a big roll of the dice".
"Obviously, the Japanese think there's some benefit to be had from this, and we are not going to prevent an individual country from using their resources," he added.