What is Prepandrix?
Prepandrix is a vaccine that is given by injection. Contains fractions of influenza viruses that have been inactivated (killed). The vaccine contains a strain of the influenza virus named "A / VietNam / 1194/2004 NIBRG-14" (H5N1).
What is the vaccine used for?
Prepandrix is a vaccine intended for adults to protect against the flu caused by the H5N1 strain of influenza A virus. The vaccine is administered based on official recommendations.
The vaccine can only be obtained with a prescription.
How is the vaccine used?
The vaccine is given by injection into the shoulder muscle in two single doses, at least three weeks apart. Adults over the age of 80 may need a double dose of the vaccine (one injection in each shoulder) with a second double dose three weeks later.
How does the vaccine work?
Prepandrix is a "prepandemic" vaccine. It is a special type of vaccine designed to protect against a strain of influenza that can cause a future pandemic. An influenza pandemic occurs when a new type of influenza virus is detected that can be easily transmitted from person to person due to the absence of immunity (protection) among the population. A pandemic can affect most countries and regions of the world. Health experts express concern as a future flu pandemic could be caused by the H5N1 strain of the virus. The vaccine was designed to provide protection against this strain so that it can be used before or during an influenza pandemic.
Vaccines act by "teaching" the immune system (the body's natural defense system) to defend itself against a disease. This vaccine contains small amounts of hemagglutinins (surface proteins) of the H5N1 virus. The virus was first inactivated so as not to cause any disease. When a person is vaccinated, the immune system recognizes the virus as "foreign" and produces antibodies against that virus. In case of exposure to the virus after vaccination, the immune system will be able to produce antibodies more quickly. The body will then be able to protect itself from diseases caused by this virus.
Before use, the vaccine must be prepared by mixing a suspension containing the virus particles with an emulsion. The resulting "emulsion", which will be injected, contains an "adjuvant" (an oil-based compound) to stimulate a better response.
What studies have been carried out on the vaccine?
The main study on the vaccine included 400 healthy adults aged between 18 and 60 and compared the ability of different doses of vaccine, with or without adjuvants, to trigger the production of antibodies ("immunogenicity"). Participants were given two vaccine injections containing one of four different doses of hemagglutinin. The injections were performed at an interval of 21 days from each other. The main measures of effectiveness were the levels of antibodies against the flu virus in the blood at three different times: before vaccination, on the day of the second injection (day 21) and 21 days later (day 42).
A further study examined the immenity of single or double doses of the vaccine in 437 people over the age of 60.
What benefit has the vaccine shown during the studies?
According to the criteria defined by the Committee for Medicinal Products for Human Use (CHMP), a prepandemic vaccine must induce protective levels of antibodies in at least 70% of vaccinated people to be considered adequate.
The study revealed that the vaccine, containing 3.75 micrograms of hemagglutinin and adjuvant, caused an antibody response that met these criteria. 21 days after the second injection, 84% of the vaccinated people had antibody levels capable of protecting against H5N1.
In older people, even single doses of this vaccine met these criteria, except for the small number of patients over the age of 80 who had no protection against the virus at the start of the study. These patients needed double doses of vaccine for protection.
What is the risk associated with the vaccine?
The most frequent side effects observed with the Prepandrix (occurring with over one in 10 doses of the vaccine) are headache, arthralgia (joint pain), myalgia (muscle pain), reactions at the injection site (induration, swelling, pain and redness), fever and fatigue. For the full list of side effects reported with the vaccine, see the Package Leaflet.
The vaccine should not be given to people who have had an anaphylactic reaction (a serious allergic reaction) to any of the components of the vaccine or to any substance found in very low quantities in the vaccine such as eggs, chicken proteins, ovalbumin (protein present in the vaccine). egg white), formaldehyde, gentamicin sulfate (an antibiotic) and sodium deoxycholate. Vaccination should be delayed in people experiencing sudden febrile access.
Why was the vaccine approved?
The CHMP decided that the benefits of Prepandrix are greater than its risks for active immunization against the H5N1 subtype of influenza A virus. The committee recommended the granting of the marketing authorization for the vaccine.
Other information on the vaccine
On 26 September 2008, the European Commission granted a marketing authorization for Prepandrix, valid throughout the European Union, to GlaxoSmithKline Biologicals SA. This authorization is based on the authorization issued to Prepandrix in 2008 ("informed consent").
For the full EPAR of the vaccine, click here.
Last update of this summary: 07-2009.
