Authorities routinely monitor vaccines for any signals of problems, such as the allergic reactions that do occur, rarely, every year. Company spokeswoman Gwenan White said that GlaxoSmithKline advised medical staff in Canada ast week to refrain from using one batch of the vaccine while they look into reports that that it might have caused more allergic reactions than normal.
Six people in Canada had suffered an allergic reaction, said Tim Vail, the spokesman for Canada's health minister. The batch contained about 170,000 doses. It was not immediately clear how many had been administered, although Vail said the majority had been.
"We're not seeing any thing wild or spooky or crazy about our vaccine at all," Vail said, arguing it may have been a statistical anomaly that the reactions occurred.
GlaxoSmithKline is only investigating the one batch of its swine flu vaccine in Canada. White said no other doses of its swine flu vaccine around the world are affected.
White said U.K.-based GlaxoSmithKline wrote to Canadian health care professionals advising them to stop using the batch on Nov. 18. She says a total of 7.5 million doses of the vaccine have been distributed in Canada.
Dr. Joel Kettner, Manitoba's chief medical officer of health has said they are being cautious and are following the advice. He urged people not to be alarmed, saying that any allergic reactions occur shortly after inoculation, don't last long and have not led to long-term health problems.
The provincial Alberta government was also holding back the vaccine, although it had not seen a jump in reactions.
GlaxoSmithKline is the world's second largest drug maker by revenue. Its shares were up 0.08 percent on the London stock exchange at 1,278.50p ($21.19)
Associated Press Writer Rob Gillies in Toronto contributed to this report.