OTTAWA – A batch of swine flu vaccine is being pulled back for investigation after it appeared to cause higher rates of severe allergic reactions than other lots.

GlaxoSmithKline Inc., which is producing the Canadian order of H1N1 influenza vaccine at its plant in Ste-Foy, Que., said it asked provincial and territorial health authorities Wednesday to stop using doses from a specific lot shipment distributed late last month.

"(GlaxoSmithKline) is taking this cautionary action because (the Public Health Agency of Canada) has received a higher than expected number of reports of anaphylaxis in this lot number compared to other lots," company spokeswoman Megan Spoore said in a statement. "On an ongoing basis (GlaxoSmithKline) is working with Health Canada to ensure that each vaccine lot released to the provinces and territories consistently meets quality and safety standards."

The batch under investigation by the federal government and GlaxoSmithKline bears the lot number A80CA007A brand name Arepanrix, which is the version that contains adjuvant, a chemical additive that stretches supply and boosts immunity.

Manitoba health officials say they have noticed severe allergic reactions from the batch in question at a rate of one in 20,000, which is much higher than the normal rate of one in 100,000.

A spokesman for the Ontario health ministry said 1,500 doses of this vaccine were distributed to Ontario and sent to two public health units: Perth Health Unit and Renfrew Health Unit.

"This vaccine was not administered to any persons and is being withheld until the analysis is complete," David Jensen wrote in an email Friday.

Meanwhile, federal Health Minister Leona Aglukkaq announced during Question Period in the House of Commons Friday that provinces and territories can expect to receive 4.8 million doses of the H1N1 vaccine by the end of next week.

Ontario is expected to receive 1.86 million of those doses.

That would bring the total number of doses shipped across the country by Nov. 29 to 15.3 million.

The Public Health Agency of Canada has released its first weekly surveillance report for the H1N1 influenza pandemic vaccine since the immunization campaign began three weeks ago and the data show that from Oct. 21 to Nov. 7 – when 6.6 million doses had been shipped across the country – only 36 people experienced serious adverse events including life-threatening allergic reactions called anaphylaxis and febrile convulsions brought on by high fever.

That number includes one death from anaphylaxis that is currently being investigated and which a spokeswoman for the Quebec health ministry has confirmed was an octogenarian who died in that province two weeks ago.

"With any vaccination campaign, we expect to see some cases of serious adverse events," Dr. David Butler-Jones, Canada's chief public health officer, said at a news conference Tuesday.

"They are very rare, but they are part of all mass vaccination campaigns and we expect to see a small number of them."

The rate of serious adverse events is so far 0.54 per 100,000 doses distributed, which Butler-Jones noted is less than what is generally expected for the seasonal flu vaccine.

An additional 598 milder adverse reactions were reported during the same time period. The majority of those involved nausea, dizziness, headache, fever, vomiting and swelling or soreness at the site of the injection.

There were also several reports of allergic reactions with a range of symptoms, from hives and skin rashes to tingling lips or tongue and difficulty breathing. Most of those occurred within minutes after people received their shot in the arm and staff at the flu clinics treated them right away.

With files from The Canadian Press.