Recommendations for the Use of the H1N1 Flu Vaccine

Updated: November 13, 2009

The Government of Canada has authorized the use of the adjuvanted  H1N1 flu vaccine, which is called AREPANRIX, and the unadjuvanted H1N1 flu vaccine, both of which are  manufactured by GlaxoSmithKline (GSK).

In an effort to secure additional unadjuvanted vaccine for pregnant women as soon as possible, the Government of Canada has also authorized access to Australia’s CSL Biotherapies Inc. unadjuvanted H1N1 flu vaccine, which is called Panvax H1N1.

Getting the H1N1 flu vaccine is the best way for Canadians to protect themselves and others from getting infected. The Government of Canada has ordered enough vaccine for all Canadians who need and want protection.

Certain groups of people are more at risk for complications of the flu, and will be encouraged to get the vaccine as soon as possible. These groups include pregnant women, people with chronic diseases, and children under the age of five. For more details, see our information on vaccine sequencing.

Vaccine Details

Both the adjuvanted and unadjuvanted vaccine are 0.5 ml doses that contain a dead version of the H1N1 flu virus to help train the immune system to fight off infection.

The adjuvanted vaccine includes a booster element that helps the immune system develop a stronger defence against infection. For the H1N1 flu vaccine, the adjuvant is made up of a combination of naturally occurring oil (called squalene), water, and vitamin E.

Both vaccines contain a small amount of thimerosal. Thimerosal is a form of mercury used in the H1N1 flu vaccine to stabilize it and maintain its quality during storage. Thimerosal is a different form of mercury than the mercury known to cause health problems. The amount of mercury in the H1N1 flu vaccine is much less than the daily limit recommended for environmental exposure to mercury. For example, there is significantly less mercury in the vaccine than you would find in a can of tuna fish.

Both vaccines also include trace amounts of egg protein, as the vaccines are developed by growing virus in eggs.

Safety & Efficacy Data

Canada is confident in the safety and efficacy of the H1N1 flu vaccine. While it has been approved based on preliminary clinical trial data, scientific evidence shows that the adjuvanted vaccine is safe.  Recommendations for use may be modified as more clinical trial data becomes available.

What we’ve learned from early clinical trials, and from trials completed on a vaccine with the same adjuvant that was created for the H5N1 flu (also called avian or bird flu) is:

• Adults immunized with the H1N1 flu vaccine developed a strong immune response within 21 days of receiving one dose.
• Receiving a seasonal flu vaccine did not affect the level of immunity achieved from the H1N1 flu vaccine.
• Children developed a stronger immune response after receiving two half doses of adjuvanted H5N1 flu vaccine than two doses of unadjuvanted.

Dosing and Vaccine Type

National recommendations on the use of H1N1 flu vaccine have been developed based on the latest scientific evidence, including clinical trial results.  The Government of Canada has monitored vaccine use internationally and has found that both types of vaccine, adjuvanted and unadjuvanted, offer safe and effective protection from the H1N1 flu virus. Recent evidence has shown that adjuvanted vaccine offers better protection for children than unadjuvanted vaccine, but for most people between 10 and 64 years of age, both the adjuvanted and unadjuvanted vaccines provide an excellent immune response, The recommendations for the use of vaccine have been updated to reflect these findings.

The recommendations include:

• Children between 6 months of age and under 3 years of age should receive two half-doses of adjuvanted H1N1 flu vaccine, administered at least 21 days apart.  Guidance for children in this age group is unchanged.
• Children with chronic health conditions who are between 3 and 9 years of age should receive their first half-dose of the H1N1 flu vaccine as soon as possible.  They should also receive a second half-dose of the H1N1 flu vaccine.  The interval between the two half-doses should be a minimum of 21 days.
• Healthy children between 3 and 9 years of age should only receive a single half-dose of the H1N1 vaccine, and do not need to return for a second vaccine for now.
• Healthy people between the ages of 10 and 64 years should receive one dose of either the adjuvanted or unadjuvanted vaccine.
• Pregnant women should receive one dose of the unadjuvanted vaccine. In cases where the unadjuvated vaccine is unavailable and H1N1 flu rates are high or increasing in the community, women more than 20 weeks pregnant and women less than 20 weeks pregnant with serious chronic diseases should be offered one dose of the adjuvanted vaccine.
• People over the age of 64 and people with weakened immune systems should receive one dose of the adjuvanted vaccine.

These recommendations may be updated as more information becomes available.

Based on advice from the World Health Organization earlier this year, the Government of Canada ordered 1.8 million doses of unadjuvanted vaccine to offer pregnant women, since adjuvanted vaccine has not been widely tested in this group.  However, all data to date indicates that adjuvanted vaccine is as safe as unadjuvated vaccine.

Both types of the H1N1 flu vaccine can be administered along with seasonal influenza immunization and other vaccines.  Consult with your health care provider for additional information on whether you should receive both the H1N1 flu and the seasonal flu vaccine.

Who Shouldn’t Get the Vaccine?

The H1N1 flu vaccine is not approved for children under six months of age.

You shouldn’t get the H1N1 flu vaccine if:

• You have had a previous anaphylactic (severe allergic reaction) to any element of the vaccine, OR
• You have a hypersensitivity to eggs (e.g. hives, swelling of mouth and/or throat, breathing difficulty), OR

• You currently have a high fever, OR
• You have experienced Guillan-Barré Syndrome within eight weeks of receiving a seasonal flu vaccine.

If you have a mild egg allergy, consult a healthcare provider before immunization. You may be able to be immunized with some additional precautions.

What to Expect After H1N1 Immunization

An adverse event is any unwanted medical reaction following immunization.  The majority of adverse events are minor reactions. Canada has a strong vaccine safety surveillance program in place to report and investigate any serious or unexpected reactions to the vaccine.

Clinical trials found the most common reactions after getting the adjuvanted vaccine were minor and included pain, swelling and redness at the injection site. This is to be expected because the adjuvant helps the body develop a stronger immune response by increasing the inflammatory response.

Other commonly reported reactions were fatigue, muscle and joint pain, and headache. In younger children, a fever, drowsiness, irritability and loss of appetite were also reported in low levels.

During clinical trials for CSL Australia’s unadjuvanted vaccine, no serious adverse events or unexpected adverse events were reported in preliminary findings.  The most common reactions reported were injection-site tenderness, heachache, pain, fatigue, muscle pain and nausea.