All about Pandemrix

Influenza pandemic is an outbreak of a new strain of flu virus that can spread easily from person to person due to lack of immunity (protection) of the people against this strain. A pandemic can affect most countries and regions around the world. Pandemrix should be administered in accordance with official recommendations. The vaccine is issued with a prescription.

Pandemrix. How is it used?

Pandemrix is administered by injection into the shoulder muscle. Persons who have not yet received pre-pandemic vaccine against pandemic influenza should be vaccinated with two doses of Pandemrix administered at least three weeks apart. Among adults aged over 80 years, it might be necessary to double the dose of Pandemrix (an injection in each shoulder) and administering a second double dose three weeks later. In people who already received a pre-pandemic vaccine containing a virus strain similar to that causing the pandemic, a single dose of Pandemrix is sufficient.

Pandemrix. How does it work?

Pandemrix vaccine is a "prototype". This is a special type of vaccine developed to help cope with a pandemic. Before a pandemic breaks out, no one knows what strain of flu will be involved. So pharmaceutical companies can not adequately prepare the vaccine in advance. However they may prepare a vaccine containing a strain of influenza specially chosen for the fact that very few people were exposed, and against which very few people are immunized. They can then test the vaccine to see how people react, allowing them to predict how people will react when we include the influenza strain causing the pandemic.

Vaccines work by "teaching" the immune system (the body's natural defenses) to defend itself against disease. Pandemrix contains small fragments of hemagglutinin (surface proteins) of a virus called H5N1. The virus was inactivated beforehand so that it can not induce disease. If a pandemic begins, the virus strain present in Pandemrix will be replaced by the strain causing the pandemic before a vaccine can be used.

When the vaccine is administered, a person's immune system recognizes the virus as "foreign" and produces antibodies against it. In a further exposure to the virus, the immune system is able to produce antibodies more quickly, thus helping protect the body against disease caused by this virus.

Before use, the vaccine will be prepared by mixing a suspension containing the virus particles with a solvent. The "emulsion" result will be injected. The solvent contains an 'adjuvant' (a compound containing oil) to help achieve a better response.

What studies have been conducted on Pandemrix?

The main study on Pandemrix included 400 healthy adults aged 18 to 60 years and had to compare the ability of different doses of Pandemrix, with or without adjuvant, to trigger antibody production (immunogenicity). Participants received two injections of Pandemrix containing one of four different doses of HA. The injections were performed 21 days apart. The main efficacy measures were the rate of anti-influenza antibodies in the blood of patients at three different times: before vaccination, on the day of the second injection (day 21) and 21 days later (day 42) .

Another study was aimed to examine the immunogenicity of single or double doses of Pandemrix among 437 subjects aged over 60 years.

Finally, two studies were to examine the effect resulting from administration of a single injection of Pandemrix to subjects who already received a pre-pandemic vaccine containing a strain of virus related.

What is the benefit Pandemrix has had during the studies?

According to the criteria defined by the Committee for Medicinal Products for Human Use (CHMP), a prototype vaccine must induce protective antibody levels in at least 70% of those which are considered appropriate. The main study has shown that Pandemrix measured at 3.75 micrograms of HA with adjuvant induced an antibody response sufficient to meet these criteria. On the day 21 after the second injection, 84% of people receiving the vaccine showed levels of antibodies that protect against H5N1.

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