What is Pandemrix?

Pandemrix is a vaccine that is given by injection. It contains parts of influenza (flu) viruses that have been inactivated (killed). Pandemrix contains a flu strain called A/California/7/2009 (H1N1) v-like strain (X-179A).

What is Pandemrix used for?

Pandemrix is a vaccine to protect against ‘pandemic’ flu. It should only be used for the influenza A (H1N1) flu pandemic that was officially declared by the World Health Organization on 11 June 2009. A flu pandemic happens when a new strain of flu virus appears that can spread easily from person to person because people have no immunity (protection) against it. A pandemic can affect most countries and regions around the world. Pandemrix is given according to official recommendations.

The vaccine can only be obtained with a prescription.

How is Pandemrix used?

Pandemrix is given as one dose, injected into the shoulder muscle. A second dose may be given after an interval of at least three weeks. This second dose must be given in children aged from 6 months to 9 years of age.

How does Pandemrix work?

Pandemrix is a vaccine. Vaccines work by ‘teaching’ the immune system (the body’s natural defences) how to defend itself against a disease. Pandemrix contains small amounts of haemagglutinins (proteins from the surface) of a virus called A(H1N1)v that is causing the current pandemic. The virus has first been inactivated so that it does not cause any disease.

When a person is given the vaccine, the immune system recognises the virus as ‘foreign’ and makes antibodies against it. The immune system will then be able to produce antibodies more quickly when it is exposed to the virus again. This will help to protect against the disease caused by the virus.
Before use, the vaccine will be made up by mixing together a suspension that contains the virus particles with a solvent. The resulting ‘emulsion’ will then be injected. The solvent contains an ‘adjuvant’ (a compound containing oil) to enhance the immune response.

How has Pandemrix been studied?

Pandemrix was first developed as a ‘mock-up’ vaccine, using a H5N1 strain of the flu virus called A/Vietnam/1194/2004. The company studied the ability of this mock-up vaccine to trigger the production of antibodies (‘immunogenicity’) against this strain of flu virus in advance of the pandemic.

Following the start of the H1N1 pandemic, the company replaced the virus strain in Pandemrix with the H1N1 strain causing the pandemic, and presented data relating to this change to the Committee for Medicinal Products for Human Use (CHMP).

An ongoing study in 130 healthy adults aged 18 to 60 years is comparing the ability of Pandemrix H1N1 (as a two-dose schedule) to trigger an immune response with that of an experimental vaccine containing four times as much virus material and no adjuvant.

The company has precented the results of three onging studies.

- A study in 130 healthy adults aged 18 to 60 years comparing the ability of Pandemrix H1N1 (as a two-dose schedule) to trigger an immune response with that of an experimental vaccine containing four times as much virus material and no adjuvant;

- A study comparing the ability of Pandemrix as a two-dose schedule to Pandemrix as a single dose schedule to trigger an immune response in 120 healhty elderly subjects over the age of 60 years;

- A study in healthy children aged between 6 months and 35 months comparing the effectiveness of Pandemrix as a ‘full dose’ 0.5 ml with that of a ‘half dose’ 0. 25ml.

What benefit has Pandemrix shown during the studies?

The mock-up vaccine was shown to bring about protective levels of antibodies in at least 70% of people in which it was studied. In line with the criteria laid down by the CHMP, this demonstrated that the vaccine brought about an appropriate level of protection. The CHMP was also satisfied that the change of strain to the H1N1 strain did not affect the characteristics of the vaccine.

In all three ongoing studies the CHMP has looked at how the first dose was able to trigger immunity to a satisfactory level. In the study in adults, in the 61 subjects who received the marketed formulation of Pandemrix H1N1, the percentage of subjects who had a level of antibodies in their blood that was high enough to neutralise the H1N1 virus (seroprotection rate) was 100%. In the study in the elderly, this percentage was 87% (based on the data for 120 subjects), and in the study in children it was 100% (based on the data for the first 51 children included in the study).

What is the risk associated with Pandemrix?

The most common side effects with Pandemrix (seen with more than 1 in 10 doses of the vaccine) are headache, arthralgia (joint pain), myalgia (muscle pain), reactions at the site of the injection (hardening, swelling, pain and redness), fever and fatigue (tiredness). For the full list of all side effects reported with Pandemrix, see the Package Leaflet.

Pandemrix should not be given to people who have had an anaphylactic reaction (severe allergic reaction) to any of the components of the vaccine, or to any of the substances found at very low levels in the vaccine, such as egg or chicken protein, ovalbumin (a protein in egg white), formaldehyde, gentamicin sulphate (an antibiotic) and sodium deoxycholate. However, it may be appropriate to give the vaccine to these patients during a pandemic, as long as facilities for resuscitation are available.

Why has Pandemrix been approved?

The CHMP decided that, based on the information obtained with the mock-up vaccine and the information provided on the strain change, the benefits of Pandemrix are greater than its risks for the prophylaxis of influenza in the officially declared H1N1 pandemic situation. The Committee recommended that Pandemrix be given marketing authorisation.

Pandemrix has been authorised under ‘Exceptional Circumstances’. This means that it has not been possible to obtain full information about the pandemic vaccine. Every year, the European Medicines Agency will review any new information that may become available and this summary will be updated as necessary.

What information is still awaited for Pandemrix?

The company that makes Pandemrix will collect information on the safety and effectiveness of the vaccine, and submit this to the CHMP for evaluation.

Which measures are being taken to ensure the safe use of Pandemrix?

The company that makes Pandemrix will collect information on the safety of the vaccine while it is being used. This will include information on its side effects and its safety in children, the elderly, pregnant women, patients with severe conditions and people who have problems with their immune systems.

Other information about Pandemrix:

The European Commission granted a marketing authorisation valid throughout the EU for the H5N1 mock‑up vaccine for Pandemrix to GlaxoSmithKline Biologicals s.a. on 20 May 2008. The marketing authorisation for the H1N1 vaccine was granted on 29 September 2009.