Drug maker GlaxoSmithKline says new research suggests that children may need only one shot of its  swine flu vaccine to be protected from the virus, as Health Canada published instructions on how to prepare the antiviral drug Tamiflu for kids.

GSK is the company contracted to make the swine flu vaccine for the Canadian government. In a statement Friday, it said researchers have found that one dose of its vaccine was enough to boost children's immune systems to fight the virus.

The finding comes from data from an ongoing trial in Spain in 200 children aged six months to three years. The vaccine, called Pandemrix in Europe, is the same formulation as the H1N1 vaccine used in Canada, called Arepanrix, the company said in an email to CTV News. Both contain 3.75 micrograms of H1N1 antigen and GSK's proprietary adjuvant AS03.

"These first results with Pandemrix [Arepanrix] in a paediatric population show that a high immune response was elicited 21 days after one single administration of vaccine," the company said in a press release.

"In 100 per cent of the children receiving the adjuvanted vaccine, a response above the regulatory threshold of 1:40 seroprotection was elicited, which is considered indicative of protection in adults."

Experts had expected that children would need two doses to prime their young immune systems to fight off the virus.

Rival pharmaceutical company Sanofi Pasteur said earlier this month that clinical trial of its H1N1 vaccine - which doesn't include adjuvant - revealed that one dose would not be enough to protect children. And on Wednesday, the Public Health Agency of Canada advised that kids under the age of 10 should get two half-dose vaccinations given 21 days apart.

It's not known whether that advice will change, in light of these recent findings.

Kids usually need two doses of flu vaccine to build an effective immune response. The first dose acts as an "introduction" to a flu strain they've never experienced before, while the second shot "revs up" their immune response further.

But this year's swine flu vaccine, unlike seasonal flu vaccine, contains an adjuvant that boosts immune response.

Further results on the H1N1 clinical trials will follow as more data become available, GSK said, noting that data on the vaccine's effectiveness and safety in seniors is expected soon.

Meanwhile, Health Canada published a statement with instructions on how to mix the powder inside the capsules of Tamiflu with a syrup, which can be administered to young children.

That announcement came as Tamiflu manufacturer Hoffman-La Roche said it has placed a priority on producing the capsule form of the antiviral in order to meet growing demand.

As a result, the Health Canada statement warned there may be shortages of the powder formulation in some parts of the country for the foreseeable future.

While most people recover from swine flu without needing medical treatment, the virus can strike children particularly hard. According to data from the U.S. Centers for Disease Control and Prevention, more than half of hospitalizations and nearly a quarter of deaths due to swine flu are in children and adults under 25.

The World Health Organization said Friday that nearly 5,000 people have died from swine flu since it emerged this year and developed into a pandemic. WHO said there were 4,999 total deaths through Oct. 18, most of them in the Western Hemisphere. The figure was up 264 from a week earlier.

Since many countries have stopped counting individual swine flu cases, the figure is considered an underestimate.

With files from The Canadian Press