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A technician holds a master H1N1 virus sample, for the pre-production of a vaccine against pandemic H1N1 influenza Avirus at a GlaxoSmithKline laboratory in Dresden, Germany.

The federal government will order 50.4 million doses of swine flu vaccine, and will pick up 60 per cent of the cost, Health Minister Leona Aglukkaq announced Thursday.

The number of doses is enough for all Canadians who want and need to be vaccinated against the H1N1 pandemic virus, said Dr. David Butler-Jones, chief public health officer of Canada.

The total cost will be more than $400 million, Butler-Jones told reporters.

A spokesperson for the pharmaceutical company GlaxoSmithKline said the entire order for the vaccine will be produced at its factory in Quebec City.

Canada's pandemic influenza plan calculated that about 75 per cent of Canadians might want or need to be vaccinated during a pandemic.

Results from trials of the avian flu vaccine suggest one dose should be enough, particularly since Canada's flu vaccine supplier, GlaxoSmithKline, is using an additive known as adjuvant, he said. Adjuvants are used to boost immune response from vaccines.

The vaccine order is large enough to give one dose to every Canadian, or two doses to 75 per cent of the population, he said.

Rapid test misses infections

Also on Thursday, the U.S. Centers for Disease Control and Prevention concluded rapid tests to diagnose swine flu are often wrong, based on 65 respiratory specimens collected during April and May.

The study, published in the agency's Morbidity and Mortality Weekly Report, looked at rapid tests from three manufacturers. The rapid tests take about 15 minutes and are given while a patient is waiting at a doctor's office.

The overall sensitivity of the tests for detecting the influenza A H1N1 virus in respiratory specimens ranged from 40 to 69 per cent, meaning many infections will be missed, especially when viral levels were low, the researchers said.

For those with negative results on the rapid tests, doctors should decide whether to prescribe antiviral medications and order more testing based on their clinical suspicion, the patient's underlying medical conditions, severity of illness, risk of complications, and circulating flu strains, the CDC recommended.  

The samples in the study were evaluated using a slower but more accurate test called real-time reverse transcription-polymerase chain reaction, which looks for genetic material from the virus.

"If we did need two doses for everybody and everybody in the country wanted to be and needed to be immunized, then we would at that point have to order more," Butler-Jones said.

Polling done for the Public Health Agency of Canada suggests about 60 per cent of Canadians may want pandemic flu shots. The agency recommends the vaccine to slow down the spread of H1N1 virus, and for people to protect themselves and their families, he added.

First Nations and Inuit will have access to the pandemic vaccine once it's available, Aglukkaq said.

Vaccine safety

In Canada, pandemic vaccine production is on target, Butler-Jones said, with clinical trials set to begin in late September. People could start receiving shots in November, if not sooner, he said.

Butler-Jones said that risks of swine flu far outweigh any theoretical risks of the adjuvanted vaccine, including for groups such as pregnant women and children.

"We will be monitoring it closely when it comes on to the market, and if there are any concerns, they'll be addressed," he said in an interview.

Public health officials could offer vaccine without adjuvant for some people, said Dr. Allison McGeer, an infectious disease specialist in Toronto.

"We get back to, if I can vaccinate 200,000 women instead of 50, 000 women, that may be the right thing to do," McGeer said. "Or it may be that we'll get enough data from the Southern hemisphere about the actual risk in pregnancy to know that we don't need to offer it to all pregnant women."

Earlier on Thursday, an official with the World Health Organization said the first swine flu vaccines will likely be approved by regulators in September.

Manufacturers initially said they were finding low yields in making vaccines for the H1N1 pandemic strain of the virus, but that it is now improving.

"We are on track in development," Marie-Paule Kieny, WHO director of the Initiative for Vaccine Research, told a news conference in Geneva.

Small batches of the pandemic vaccine have been made and clinical trials have started in Australia, China, the United States, Germany and Britain, with more set to begin.

Creating the batches and giving the shots to people are two separate steps, Kieny said, noting various regulators must first license the vaccine for use.

Kieny also aimed to quell fears about the safety of the pandemic vaccine, saying it is based on proven technology, and much is known about seasonal flu vaccines that would also apply to H1N1.

She said the agency expects to see reports of side effects once millions of people have received the vaccine, but that deadly side effects will be rare. Vaccines commonly provoke reactions such as nausea, fever, pain from the injection, and diarrhea.

"We see no apparent safety signal," she said. "There is no safety concern with using adjuvanted vaccine."

With files from The Associated Press