Should you be immunized against the H1N1 influenza? That depends on who you are, where you live and when you ask. Notwithstanding the increasingly hard sell from some public-health authorities, the truth is that the vaccine will be too late to be of real value for many Canadians.
H1N1 is already active in many parts of Canada. It's an early flu season, but a relatively mild one. "Mild" still means that more than a million Canadians will get a little sick and a small number will get very ill. But this is no more than we expect every year from influenza.
We had the measure of H1N1 even before we had a vaccine. Our health-care system will not be overwhelmed. Commerce will not grind to a halt. Women are no more vulnerable than men. Mortality rates are highest in people of middle age or older.
Two-thirds of severe illness and death will be in people with serious underlying medical problems.
Healthy people have little to fear from H1N1. The virus itself has not changed. About one in 20 will develop an unpleasant but short-lived "flu." Their chances of dying from H1N1 are about 1 in 250,000. The same healthy person is about 20 times more likely to die this year from a motor-vehicle crash.
Over the next few weeks, we will see a few more deaths in otherwise healthy young people - because more people are getting infected than in a usual flu season. Unfortunately, these individual tragedies will be blown out of proportion by the media.
In addition to people with underlying medical problems, H1N1 tends to be more severe in pregnant women and in children under the age of 5. Babies under six months of age are also vulnerable but cannot be immunized. (People living with a young baby should be immunized to avoid bringing the virus home.)
The Canadian government is boasting that there is enough vaccine for everyone. This is a tad disingenuous. The vaccine is arriving in weekly aliquots of two million to three million doses. We don't actually have enough vaccine to immunize everyone right now. And, as it turns out, timing is a crucial issue for many Canadians.
Local flu outbreaks typically peak within four or five weeks and then drop off rapidly. The vaccine takes time - probably a week - to provide protection after it is given. When H1N1 is gone, it's almost certainly gone for this flu season.
The worst of H1N1 will have passed from some areas of Canada - Southern Ontario and the lower mainland of British Columbia, at least - before healthy people can even roll up their sleeves.
The new adjuvanted influenza vaccine is safe and effective. The risk of a significant reaction is extremely small. But we don't immunize people just because we can. We're supposed to base our recommendations on expectations of benefit.
Quite appropriately, public-health authorities are giving priority to immunizing the most vulnerable. They should get immunized as quickly as possible. Two-thirds of all immunization benefits will come from protecting these small groups. Everyone else should wait. It's far too late to apprehend the outbreak anyway.
So what about the healthy general public?
If the vaccine becomes available to you before H1N1 hits your part of the country, then it's entirely reasonable to be immunized. It's also reasonable to take a pass. The anticipated benefits from immunization are very small, and the risks are tiny. But if H1N1 has already peaked in your community, these benefits drop off dramatically. It's too late.
But there is a place where our surplus Canadian vaccine - all 30 million doses or so - can do some real good. Send it to developing countries that will soon face a second wave of H1N1 without a vaccine, antiviral drugs or intensive-care units to assist their most vulnerable.
There's still time to do that.
Richard Schabas was Ontario's chief medical officer of health from 1987 to 1997. Neil Rau is an infectious diseases specialist and medical microbiologist in private practice in Oakville, Ont., and a University of Toronto lecturer.