A single dose of H1N1 vaccine should be adequate for all age groups, even very young children, and pregnant women should feel free to use vaccine containing adjuvant, an expert committee that advises the World Health Organization on vaccine issues reported Friday.
The group, known by the acronym SAGE, said vaccines containing boosting additives called adjuvants and vaccines that are adjuvant-free appear to be equally safe and there is no need to recommend pregnant women get the latter on a preferential basis.
"This is based on the fact that the safety profiles of adjuvanted vaccine and the non-adjuvanted vaccine are very similar, and the fact that the non-adjuvanted vaccine has been recommended for pregnant women for many, many years," Dr. Marie-Paule Kieny, director of the WHO's initiative for vaccine research, said in reporting on the recommendations of the panel.
"So there is no reason, in SAGE's view, to distinguish between both types of vaccines."
The recommendations, if adopted, should stretch limited global supplies, enabling more vaccine to become available for developing countries which haven't been able to pre-order pandemic flu shots. The WHO hopes to begin distributing donated vaccine to developing countries in late November or early December, Kieny said.
A dose of vaccine with adjuvant uses one-quarter of the amount of antigen (the material that induces an immune response) used in a shot made without one of these boosting additives.
Canada is using adjuvanted vaccine, though it has purchased nearly two million doses of unadjuvanted vaccine for pregnant women and young children. It suggests, however, that young children receive adjuvanted vaccine because it is more effective in that age group.
On the issue of pediatric dosing requirements, several jurisdictions -- including Canada -- currently recommend children under 10 receive two doses of H1N1 vaccine, given at least 21 days apart. But in Canada's case at least, that may soon change.
Last week the country's vaccine manufacturer, GlaxoSmithKline, released preliminary data showing that one pediatric dose (half the size of an adult dose) of vaccine plus a half dose of adjuvant generated what looks like a protective response in 100 per cent of children aged six months to 36 months old.
When those results were released, Chief Medical Officer of Health Dr. David Butler-Jones said Canada might drop the recommendation for two doses if the findings could be buttressed with more data.
On Friday, after the WHO issued its new recommendations, Butler-Jones said experts advising the Public Health Agency of Canada are already studying whether to move to a single-dose recommendation for children.
The SAGE, which stands for Strategic Advisory Group of Experts on Immunization, admitted the data on the efficacy of a single dose in young children is limited.
And its recommendation is geared more towards the practicality of delivering vaccine in times of short supply than on a sense of certainty that one dose of vaccine -- adjuvanted or not -- would actually prevent infection across the board in young children.
"Some vaccines, notably the adjuvanted vaccines, are likely to be protective at one dose. Some may not (be)," Kieny said in an interview.
But she noted that even in cases where vaccine protection is less than ideal -- say with unadjuvanted vaccine -- having one shot would give a child some protection and should lead to less severe illness, if that child becomes infected with H1N1.
"They may not be all immunogenic enough to reach the value to have a registration for that age," Kieny said.
"But in view of the fact that for the time being there is not enough vaccine even for the countries who want to vaccinate children and will have access to a lot of vaccine, in these circumstances it would be better to give the maximum of children one dose rather than to insist to give each of the children two."
In saying there is no reason to differentiate between adjuvanted and unadjuvanted vaccine for pregnant women, the WHO's advisory group reversed its earlier recommendation that countries try to offer adjuvant-free vaccine to this group, which is at significantly higher risk from this virus than the rest of the population.
Between seven per cent and 10 per cent of all H1N1 patients sick enough to need hospital care so far have been pregnant women, the WHO noted.
Canada, which had initially planned only to buy vaccine with adjuvant, ordered special supplies of adjuvant-free vaccine in response to the SAGE's earlier recommendation.
On Thursday, federal officials said switching GSK's production line from adjuvanted to non-adjuvanted and then back again would slow down the flow of vaccine in the country over the next two weeks.
Some provinces have said they may need to cut back on their vaccine clinics as a result.
The WHO advisory group said animal studies of adjuvanted and non-adjuvanted vaccines as well as live-virus vaccines (not used in Canada) found "no evidence of direct or indirect harmful effects on fertility, pregnancy, development of the embryo or fetus, birthing, or post-natal development."
Kieny said so far the safety profile of the H1N1 vaccines is good. No unusual adverse effects have been reported. Some side-effects have been reported but they are of the type seen with seasonal flu shots, the WHO said in a statement posted on its website.
Fifteen countries have started to vaccinate against the virus: Australia, China, Japan, Sweden, the United States, Belgium, Finland, France, Norway, Britain, Austria, Canada, Germany, Portugal and South Korea. Kieny said at this point several hundred thousand doses of vaccine have been administered.
The SAGE also viewed the available evidence on whether it is safe to give seasonal and pandemic flu shots at the same time.
The group said so-called co-administration of the two types of flu shots is safe, though live-virus vaccines should not be given at the same time.
