OTTAWA - SIX severe allergic reactions to swine flu vaccinations have been observed in Canada, health authorities said on Tuesday, adding that all of the individuals are feeling better.

All of the cases of anaphylactic shock were linked to a single batch or 172,000 doses of Aprepanrix vaccines made by GlaxoSmithKline (GSK) distributed starting Nov 2, said Caroline Grondin, a spokeswoman for Canada's health ministry. Distribution of the batch to six provinces - British Columbia, Alberta, Saskatchewan, Manitoba, Ontario and Prince Edward Island - was halted, she said.

The health ministry believes the number of adverse reactions is abnormally high and has asked officials to investigate. One allergic reaction in 100,000 doses is the currently accepted norm.

Anaphylactic shock is a severe, rapid and sometimes fatal allergic reaction to a foreign substance such as a vaccine, shellfish or insect venom. Symptoms include difficulty breathing and a sudden drop in blood pressure.

It is a serious medical issue, said Ms Grondin, but anyone who received the vaccines and did not have a reaction should not worry.

The World Health Organization (WHO), which first alerted health authorities of potential problems with this batch of vaccines, has not changed its recommendations regarding swine flu vaccines.