OTTAWA - The Canadian Forces reserves the right to order its soldiers deployed in Afghanistan to take the vaccine meant to prevent swine flu, says the military's surgeon general.

But Commodore Hans Jung said it would be an order of last resort that will need to be studied to ensure it doesn't violate the Charter of Rights and Freedoms.

Just how far the military can go in ordering illness-prevention measures is a sensitive topic given the bruising legal fights almost a decade ago over anthrax injections.

The current plan is to make the H1N1 vaccine, expected to be available in November, voluntary for soldiers, sailors and aircrew throughout the Canadian Forces, including those on duty in Kandahar and elsewhere around the world.

But the nightmare scenario of an army laid up with the flu isn't far from minds of commanders.

"The option of mandatory (injections) is a hip-pocket issue. It's a card that would be played in a truly dire circumstances," Jung said in a recent interview with The Canadian Press.

"We're going to be strongly recommending that everybody take the vaccine offered. Obviously depending on how the pandemic evolves in Canada and around the world, the government and the military may have to think about" ordering soldiers to take it.

Jung said the chief of defence staff, the country's top military commander, has the necessary legal authority to make it happen, as seniors commanders did during the 1990s, when troops, sailors and air crew heading to the Middle East were required to take anthrax vaccinations.

Those who refused were brought up on disciplinary charges and court martialed.

The practice of mandatory anthrax injections, which made some soldiers sick and raised fears among them of Gulf War Syndrome, ended in 2000 on the orders of military judge Col. Guy Brais.

He ruled the program was violation of a soldier's constitutional rights.

Jung took over as surgeon general and head of the military's health branch in the summer.

He said the possibility of a swine flu pandemic, with an army fighting in the field, presents National Defence and the military's health services branch with a unique challenge. He described the policy as in "evolution."

There is growing public skepticism about the H1N1 vaccine. Canada has ordered more than 50 million doses from GlaxoSmithKline.

For military members stationed at home, the system of immunization isn't much different from that for ordinary citizens.

Health Canada officials have repeatedly stressed that the swine flu vaccination will not be mandatory for Canadians and Jung said that includes members of the military.

But overseas it's a different matter, where the army's health services branch has set a goal of voluntarily immunizing between 60 and 70 per cent of the roughly 2,850 Canadians serving in Kandahar.

Jung said if they don't get that figure and the flu is severe, commanders would have to look at a mandatory system.

One of the complicating factors in that equation is that Canadian troops share the airfield with more than 15,000 other NATO troops and patrol through regions where Afghans have little access to basic medical care and sanitation.

Jung said he's confident they'll get enough volunteers and said much depends on the severity of the anticipated second wave.

The military is watching the computer simulations on the potential spread H1N1. The contingency plans at National Defence range from a mild outbreak, similar to the seasonal flu, all of the way up to aid to the civil power in the event of a pandemic as serious as the 1918-19 Spanish flu.