An expert in infectious diseases and vaccines is pushing the Public Health Agency of Canada to make a safer form of H1N1 vaccine available to babies.

The federal government has ordered 50.4 million doses of vaccine, most of which contain an adjuvant — a substance used to boost the vaccine's effectiveness.

The 1.2 million doses that won't include the adjuvant are intended for pregnant women because little research has been done on the effect an adjuvant would have on them.

'I wouldn't want to rush into using the adjuvanted product without there having been a reasonable number of clinical trials in that [infant] age group.'— Dr. David Scheifele

Likewise, there's little known about how a baby would react to an adjuvant, but there are no plans to use adjuvant-free vaccines on infants.

So some doctors and public health officials are pushing the federal government to make vaccine without adjuvant available to babies aged six to 18 months, at least until there is more research on whether it causes any side-effects in that age group.

"I wouldn't want to rush into using the adjuvanted product without there having been a reasonable number of clinical trials in that age group," said David Scheifele, a pediatric infection specialist and director of the vaccine evaluation centre at British Columbia's Child and Family Research Institute.

Research is showing the adjuvant used to boost the H1N1 vaccine is safe and effective for adults. The company under contract to produce Canada's H1N1 flu vaccine, GlaxoSmithKline, is conducting other studies now.

"We'll be very, very confident about the adjuvanted vaccine, which we know in addition to providing some better immunity, appears to provide longer-lasting immunity in previous trials as well as protection against drift or changes in the virus itself," Dr. David Butler-Jones, Canada's chief public health officer, said Wednesday.

Babies and pregnant women are two of the groups on Canada's priority list for the H1N1 vaccine because they are most likely to develop severe symptoms if infected with the pandemic virus.

Canadian clinical trials that are about to begin at 30 sites across the country will include some babies over six months of age. When that data is in — likely in a couple of months and possibly after vaccination clinics have started delivering shots — a change in policy on giving young children the adjuvanted form of the vaccine could happen, Butler-Jones said.

British cases

In other H1N1 vaccine news, U.S. President Barack Obama said Thursday that the United States will share 10 per cent of its swine flu vaccine supply with other countries through the World Health Organization.

Canada could also share any excess doses, Butler-Jones has said.

Meanwhile in England, health officials announced Thursday that swine flu cases increased slightly last week, mostly in school-aged children.

Last week, there were about 5,000 new cases reported, compared with about 3,000 new cases the previous week. Experts are watching whether cases surge in the northern hemisphere this fall as schools reopen and temperatures drop. Flu viruses generally survive better in cold weather.

With files from The Associated Press