Health Canada has approved the H1N1 vaccine, meaning the first Canadians to take part in Canada's largest-ever immunization campaign could get their shots as early as the end of the week.

In Quebec, 430,000 doses are ready to be administered as of Monday. The first shots will go to health care workers, pregnant women, children under six, and those with chronic diseases.

The announcement comes a day after an 87-year-old woman succumbed to H1N1, Quebec's first fatality in this second wave of the virus.

"The second wave of the virus has arrived in the province of Quebec. The vaccine, as far as we know, is really efficient. It provides protection antibodies in 95 to 97 per cent of the people receiving the vaccine after ten days. It is secure; thousands of people have received the vaccine without major signs of any problem," said Public Health Minister Alain Poirier.

Federal Health Minister Leona Aqlukkaq announced Wednesday that two million doses of the vaccine have already been shipped to the provinces and territories, who will administer vaccination programs through flu clinics offered by local health units.

"I encourage all Canadians to get vaccinated, since there is simply no better way of fighting the H1N1 virus," said Aqlukkaq.

GlaxoSmithKline hopes to ship around 3 million doses a week to the provinces.

David Butler-Jones, Canada's chief public health officer, encouraged all Canadians to get the vaccine, if not to protect themselves, then to protect those around them.

"Frankly, I don't want to be the cause of someone's serious illness or death," he said noting that recent data suggest that those under 25 are at highest risk of serious illness from this new virus.

He added that any side effect risks from the vaccine are remote.

"Serious adverse events following immunization are rare. For the seasonal flu shot, the rate of reported serious events is about one in every million people immunized. The benefits of immunization - the prevention of serious illness and death - far outweigh any theoretical risks," he said.

Safety, effectiveness data from European studies

Canadian clinical trials of the vaccine are still underway, and the results won't be available until next year, so federal health authorities have relied on data from clinical trials done on the same vaccine in Europe. Those trials have found the vaccine safe.

The adjuvant used in Canada's swine flu vaccine, AS03, has also been tested in about 45,000 people around the world using a "mock" H5N1 vaccine. No significant safety concerns were detected, Health Canada reports. Canada has never approved a flu vaccine containing an adjuvant before.

The Canadian clinical trials are expected to add to the safety and effectiveness data, by focusing on the vaccine's effects in select population groups, such as First Nations, people who are HIV-positive, children and pregnant women.

Because some reactions from vaccines are so rare they arise in only one in a million cases, the final picture of the vaccine's safety won't be clear until after the immunization program is underway, Health Canada has acknowledged.

Butler-Jones said adults will need one dose of swine flu vaccine, but children under the age of 10 will need two, just as they do with seasonal flu shots. The vaccine is not intended for infants younger than six months.

And while pregnant women are encouraged to receive the vaccine without the adjuvant, if the unadjuvanted vaccine is delayed, they should get the regular swine flu shot to protect themselves and their babies, since pregnant women are at much higher risk of complications from the flu.

About 4,700 people worldwide have died of H1N1 to date, including 83 deaths in Canada. Another 300 or so Canadians have required care in intensive care in hospital.

The Public Health Agency of Canada says everyone aged six months and older should get the vaccine, but those who will benefit most, and those who care for them, include:

- People under 65 with chronic health conditions. (These include: heart disease, diabetes, asthma lung disease, kidney disease, liver disease and severe obesity.)

- Pregnant women

- Children aged six months to less than five years

- People in remote and isolated communities

- Health care workers involved in the delivery of essential health care services

- Household contacts and care providers of persons at high risk who cannot be immunized

Anyone over the age of 10 should receive one dose of adjuvanted vaccine. Children between six months and 10 years of age should receive the adjuvanted vaccine in two half-doses, administered at least 21 days apart. The vaccine is not recommended for children under the age of six months.

With files from CTV News Staff