Health officials across Canada are being asked to hold back a batch of swine flu vaccine that appears to be causing higher rates of severe allergic reactions.

The vaccine's manufacturer, GlaxoSmithKline, is asking governments to stop using vaccine doses from one particular lot shipment issued in late October.

The company says it's a cautionary move, pending an investigation.

Manitoba health officials say they have noticed severe allergic reactions from the batch in question at a rate of one in 20,000.

That's much higher than the normal rate of one in 100,000.

The Alberta government is also holding back the same batch of vaccine, although it says it has not seen a jump in allergic reactions.

Manitoba's chief medical officer of health, Dr. Joel Kettner, says he wants to assure people that the risk of any adverse effects from the vaccine is very low.

Health officials say the batch being investigated is fairly small, so it should not have an impact on the overall supply.