Pandemic (H1N1) 2009 Influenza Update: Experience of GSK’s H1N1 adjuvanted vaccine, Pandemrix™, and preliminary paediatric results

Issued: 23 October 2009, London UK

GlaxoSmithKline (GSK) today announced that, to date, more than 150,000 people have received GSK's pandemic H1N1 vaccine, Pandemrix™, as part of Government initiated vaccination programmes across Europe which commenced last week. Additionally, over 2,000 people have received Pandemrix in clinical trials which are ongoing.

To date, data have demonstrated that the H1N1 adjuvanted vaccine has a similar tolerability profile to GSK’s previously EMEA approved H5N1 adjuvanted vaccine.  The immune response elicited by Pandemrix has previously been reported in a limited number of adults demonstrating over 98% of the subjects exceeded the immunogenicity criteria as defined by international licensing authorities for a pandemic influenza vaccine. The adjuvant system in GSK’s influenza vaccine has already been tested in more than 41,000 people in GSK’s influenza programmes including the H5N1, the H1N1 and candidate adjuvanted seasonal flu vaccines.

Preliminary paediatric results

Also announced today are preliminary results from the first paediatric clinical trial assessing use of Pandemrix.  The trial in children aged 6 to 36 months, which is ongoing, shows that after a first dose of adjuvanted vaccine, a strong response was demonstrated which exceeds the immunogenicity criteria as defined by international licensing authorities for a pandemic influenza vaccine.  As planned, the vaccine in this trial contains a half dose of H1N1 antigen (1.9 µg) and a half dose of adjuvant, as compared to the adult vaccine.

"These results in young children provide clinically relevant information as they show the ability of the vaccine to induce a very high immune response suggestive of early protection after one dose, in a population where it is known to be difficult to raise such an immune response.  ” said Jéan Stephenne, President GlaxoSmithKline Biologicals.  “GSK is sharing these preliminary data with public health officials and organisations who will consider these results as they continue their efforts to develop the most effective strategies for providing protection against the H1N1 virus.  GSK also expects to have data in the elderly shortly."

This paediatric trial, which is taking place in Spain, involves 200 children aged 6 to 36 months, and has been designed to evaluate the tolerability and immunogenicity of Pandemrix.

A planned interim analysis was performed on the first 51 children recruited in this trial.  These first results with Pandemrix in a paediatric population show that a high immune response was elicited 21 days after one single administration of vaccine.  In 100% of the children receiving the adjuvanted vaccine a response above the regulatory threshold of 1:40 seroprotection was elicited, which is considered indicative of protection in adults.  The level of immune response according to the above mentioned threshold was identical between children in different age groups when the data were stratified (6 – 11 months, 12 – 23 months and 24 – 35 months).  The tolerability of the vaccine in this trial has been shown to be similar to that in the H5N1 clinical trial programme.  Once the trial is completed, regulatory authorities will review the data set and may then consider changes to the label which currently indicates a two dose schedule for the paediatric population.

These results differ from the recently publicised data¹ on an unadjuvanted H1N1 pandemic vaccine which, when used in children, demonstrated that 50% of children aged 6 to 35 months met the seroprotection benchmark set by regulatory agencies.  In general, seasonal influenza vaccines, which are unadjuvanted, elicit a lower immune response and reduced efficacy in young children compared to adults. Further results on the H1N1 clinical trials will follow as the data become available.

Supplies have been provided to governments, with more than 10 million doses already having been shipped.  Shipments are continuing and GSK anticipates increasing the amount being shipped to governments in the coming weeks as additional manufacturing regulatory approvals are received.

Further information on GSK’s development of a vaccine to protect against pandemic (H1N1) 2009, including explanation of the vaccine development process and background information on adjuvants is available on: http://www.gsk.com/media/pandemic-flu.htm

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