Canadian seniors can now help protect themselves against the intensely painful condition called shingles by getting a vaccine that becomes available today.

Merck Frosst Canada's Zostavax, the first and only vaccine to help prevent shingles, is now available at clinics and doctors' offices in Canada.

And while the vaccine isn't cheap -- about $150 for a single dose -- most people who have ever come down with a bad case of the condition would tell you it's worth it.

"A hundred and fifty dollars? I wouldn't care if it was $1,000," shingles patient Jacqueline Wilkins told CTV News. Wilkins came down with shingles last winter and lived with intense pain for more than four months.

"The pain was unreal," she remembers. "The nerve endings scream at you."

By the time she was properly diagnosed, it was too late for treatments, which need to be started within days of the first symptoms.

Shingles is caused by the same virus that causes chickenpox: varicella zoster. Anyone who has had chickenpox -- and that's just about all adult Canadians -- is at risk of shingles, which occurs when the chickenpox virus reactivates.

As the virus "wakes up," it causes itching, tingling, burning or pain , typically on one side of the body or face. It then develops into a rash with fluid-filled blisters within a few days.

The blisters, which aren't pretty and can take four weeks to heal, are not the worst of the condition. What's worse is the pain that affects almost 90 per cent of shingles sufferers over the age of 60. Patients describe it as burning, stabbing or throbbing pain.

For about half of those over 60, the pain continues for weeks or months after the blisters have healed, a condition called postherpetic neuralgia, or post-shingles pain.

People who have a weak immune system, through illness or injury, are most vulnerable to developing shingles. But even just aging can make the immune system weak enough that the virus reactivates, which is why about two-thirds of cases happen in people older than 50.

The severity of shingles and its complications increase with age, with almost 10 per cent of shingles patients 65 and older needing to be hospitalized. Others need to use steroid creams and antiviral medications to reduce the pain and shorten the illness.

The Zostavax vaccine should help reduce illness, though it doesn't offer perfect protection. In one study on more than 38,000 patients over the age of 60, the vaccine cut the risk of developing shingles by just 51 per cent.

But it does cut the risk of long-lasting post-shingles pain by 73 per cent compared with placebo. And in those who are vaccinated but do get the illness, the vaccine will help reduce the intensity and duration. It may even prevent further attacks in those who have already devloped shingles before.

For now, not many clinics and doctors' offices in Canada can offer Zostavas. That's because the vaccine has to be kept frozen to a temperature of -15�C or colder to maintain its potency; few doctors' offices have the freezers needed onsite.

Patients who want to find out where the vaccine is available in their area can visit the Zostavax.ca website, where clinics and doctors offering the vaccine are listed.