A spokeswoman for GlaxoSmithKline says the company issued that request after word that a batch of the vaccine may have led to "a slightly increased rate" of life-threatening allergic reactions.
The Canadian health ministry says six people in Canada have had allergic reactions. The batch in question contains about 170,000 doses.
The World Health Organization's vaccine chief confirms the number of people who went into anaphylactic shock after getting the vaccine in Canada was "a bit higher than normal."
But a spokesman for Canada's health minister says there doesn't appear to be a major cause for alarm. As he put it, health officials aren't seeing anything "wild or spooky or crazy" about the vaccine. He says the reports may be a statistical anomaly.