HALIFAX (CP) — The Canadian army is tracking down more than 5,000 peacekeepers to see whether they've suffered ill-effects from a vaccine, says a senior military officer.

The inoculation was meant to guard against tick borne encephalitis, a fatal brain disease common in some parts of Europe.

The move comes after Health Canada issued an advisory this summer saying there is a remote possibility that the vaccine may carry traces of Creutzfeld-Jakob disease — the human form of Mad Cow disease.

"There is no specific preventative measure, no specific treatment and more importantly, no test to tell if a person without symptoms of (Creutzfeld-Jakob) disease is infected with it," said a notice sent out members of the Forces.

The vaccine, made with blood products from Europe, is still in use and the military is now required to warn anyone getting it about the risks.

Cmdr. David Carpenter, with the military's medical branch, says the chances of anyone getting sick are extremely low.

"It is a theoretical possibility," he said in an interview from Ottawa. "It has never been shown to have happened."

The shots were given mostly to peacekeepers who toured Bosnia in the early 1990s.

No complaints have been discovered so far and Carpenter said people are more likely to get sick worrying about getting sick.

"It may in fact be less good for the health of an individual who is told of this and spends many, many years worrying about this possibility, which is infinitesimally small," he said.

The Forces has sent out letters to current and former members, asking them to check their international vaccination booklets and to report any concerns.