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New data for GlaxoSmithKline’s pre-pandemic H5N1 influenza vaccine, Prepandrix™, show administration flexibility for pandemic planning


Prepandrix™, Europe’s only approved pre-pandemic influenza vaccine, confers persistent immune response against a number of H5N1 strains

Issued: 16th September 2008, Third European Influenza Conference (ESWI), Vilamoura, Portugal

Results from two new clinical studies announced at the Third European Influenza Conference (ESWI) demonstrate that Prepandrix™, GlaxoSmithKline’s (GSK) H5N1 adjuvanted pre-pandemic influenza vaccine, confers broad cross-clade immunity that is maintained when the second dose is given many months after the first dose, and even if the second dose is formulated from a different H5N1 strain. Greater administration flexibility, adaptable to local pre-pandemic vaccination policies, could potentially reduce the impact on vital healthcare resources during the first intensive months of a pandemic.

“When indeed H5N1 would be at the basis of the next influenza pandemic, it is critical that a pre-pandemic H5N1 influenza vaccine provides broad and persistent immunity, also against drifted H5N1 strains.” said Professor Albert Osterhaus, Head Department of Virology, Institute of Virology Erasmus Medical Centre Rotterdam. “GSK’s pre-pandemic influenza vaccine has repeatedly demonstrated and now confirmed that this level of immunity can be maintained when the second dose is given many months after the first, even with a different H5N1 strain.”

The World Health Organization (WHO) considers that the world is now closer to another influenza pandemic than at any time since the last one in 1968,1 with the virus currently threatening to trigger a pandemic (H5N1) having a potential reported case fatality rate above 60%.2 The WHO has highlighted that vaccines are the most important intervention for preventing influenza and reducing its health consequences during a pandemic1.

A pre-pandemic influenza vaccine is the only vaccine which can be produced in advance and stockpiled today, allowing immediate availability in the event of a WHO declared pandemic. In contrast, a pandemic influenza vaccine can only go into production once the exact pandemic influenza strain is determined and declared, with the first doses being available a minimum of four months after the onset of a pandemic.2

The pre-pandemic influenza vaccine concept is based on using a currently circulating avian influenza virus likely to cause a pandemic, such as H5N1, to make a vaccine with the ability to raise immune protection against potential drift H5N1 strains. With experts citing immunisation with stockpiled pre-pandemic influenza vaccine as the most effective strategy for protecting entire populations,3,4 GSK’s pre-pandemic vaccine will play a critical role in pandemic preparedness planning.

“These new data show that GSK’s pre-pandemic influenza vaccine, is highly adaptable to local pandemic policies. Stockpiling of H5N1 vaccine and use of this vaccine is anticipated to provide the ability to offer protection to vaccinated individuals as well as to slow down the spread of the disease. New developments such as this make it vital for governments to continually evaluate their pandemic preparedness plans,” said Jean Stéphenne, President and General Manager GSK Biologicals. “We are actively working with governments and other organisations across the world to ensure the most effective pre-pandemic influenza vaccine is available to help protect against an influenza pandemic.”

Study Results from ESWI

AS03 adjuvanted pre-pandemic H5N1 vaccine allows highly flexible prime-boost vaccination strategy
The phase II, open, randomised study (in adults aged 18-60 years) evaluated the impact on the reactogenicity and immunogenicity when the second dose is administered between 21 days and up to six months after the first dose using GSK’s adjuvanted pre-pandemic influenza vaccine. A single booster dose of Prepandrix was administered six months after primary vaccination with either one or two dose(s) of the same adjuvanted vaccine. The results show that two vaccination doses, whether given 21 days or six months apart, elicit a comparable immune response against the vaccine strain. This confirms that the timing of administration with the second dose can be flexible and undertaken up to six months after first immunisation while maintaining the quality of the immune response. This highlights the robustness of the immunity achieved with the adjuvanted vaccine.

AS03 adjuvanted pre-pandemic H5N1 vaccine: single dose primary vaccination with clade 1 vaccine strain leads to strong immune responsiveness to clade 2 strain booster vaccination
The phase II, open, randomised study (in adults aged 18-60 years) evaluated the cross-clade* immunity with a two dose vaccination schedule using GSK’s adjuvanted pre-pandemic H5N1 influenza vaccine. A single booster dose of the pre-pandemic influenza vaccine containing a clade 2.1 strain (drifted* H5N1 strain) was administered six months after primary vaccination with either one or two dose(s) of the pre-pandemic vaccine containing a clade 1 strain (Prepandrix). The clinical trial results show that a single dose primary vaccination with a clade 1 vaccine strain leads to strong immune responsiveness to the clade 2 strain booster vaccination. In addition, re-vaccination provides rapid and notable cross-clade immune responses against both strains.

*A clade is the name given to groups of viral variants that are closely related from an evolutionary standpoint

*Drift strains are the result of small, gradual changes in the genetic material that occur through point mutations (which are random and unpredictable) resulting in alterations to the main surface proteins, haemagglutinin, and neuraminidase

Notes to Editors

About GSK’s Adjuvanted Pre-Pandemic Influenza Vaccine
GSK’s H5N1 adjuvanted pre-pandemic influenza vaccine is the first and only pre-pandemic influenza vaccine to be granted marketing authorisation by the European Commission (in 30 European states).The vaccine is an H5N1 adjuvanted pre-pandemic influenza vaccine, designed to be given before or at the onset of a declared influenza pandemic to prevent influenza caused by the H5N1 virus type (avian influenza or ‘bird flu’). GSK’s vaccine is formulated with a novel proprietary adjuvant system, which is designed to achieve a high immune response at a low dose of antigen, and to be long-lasting and active against a broad range of H5N1 strains.

GSK is the world leader in pandemic influenza product development as it is the only company to operate a flexible portfolio of licensed pandemic products, including the pre-pandemic influenza vaccine (Prepandrix), a pandemic influenza vaccine (Pandemrix) and an influenza antiviral (Relenza®).

GlaxoSmithKline Supporting Pandemic Preparedness Plans
GSK has previously announced its intention to donate 50 million doses of its H5N1 adjuvanted pre-pandemic influenza vaccine to the WHO in support of its stockpile initiative. The intended donation would help establish a much needed stockpile of pre-pandemic vaccines that can be distributed to the world’s poorest countries at short notice by the WHO. Delivered over a three-year period, it would provide enough doses of vaccine for 25 million people at two injections per person. GSK supports this proactive strategy of worldwide stockpiling of H5N1 pre-pandemic vaccine which may be able to save millions of lives by protecting some of the most vulnerable populations in the world at the outbreak of a pandemic.

GSK has already signed contracts with the US and several European countries, such as Switzerland and Finland, for the supply of its pre-pandemic vaccine and bulk antigen.

Prepandrix™, Pandemrix™ andRelenza® are trade marks of the GlaxoSmithKline group of companies.

GlaxoSmithKline (GSK) – one of the world’s leading research-based pharmaceutical and healthcare companies – is committed to improving the quality of human life by enabling people to do more, feel better and live longer. For company information, visit GlaxoSmithKline at

GlaxoSmithKline Biologicals (GSK Bio) – one of the world’s leading vaccine manufacturers, is headquartered in Rixensart, Belgium, where the majority of GSK’s activities in the field of vaccine research, development and production are conducted. GSK Bio employs more than 1,500 scientists, who are devoted to discovering new vaccines and developing more cost-effective and convenient combination products to prevent infections that cause serious medical problems worldwide. In 2007, GSK Bio distributed more than 1.1 billion doses of vaccines to 169 countries in both the developed and the developing world – an average of 3 million doses a day. Of those vaccine doses, more than one in every ten doses delivered were combination vaccines intended to prevent up to six diseases in one vaccine.

Prepandrix™, Pandemrix™ andRelenza® are trade marks of the GlaxoSmithKline group of companies.



1. WHO. Influenza Pandemic Preparedness and Response. Report by the Secretariat. EB115/44. 20 January 2005. (Accessed Aug 08)

2. Osterhaus Albert. Pre- or post-pandemic influenza vaccine? Editorial. Vaccine 2007; 25: 4983-4984.

3. Gambotto A, Barratt-Boyes SM, de Jong MD, Neumann G, Kawaoka Y. Human infection with highly pathogenic H5N1 influenza virus. Lancet 2008; 371; 1464–75

Cautionary statement regarding forward-looking statements
Under the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995, GSK cautions investors that any forward-looking statements or projections made by GSK, including those made in this announcement, are subject to risks and uncertainties that may cause actual results to differ materially from those projected. Factors that may affect GSK’ s operations are described under ’Risk Factors’ in the ’Business Review’ in the company’ s Annual Report on Form 20-F for 2007.


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