GlaxoSmithKline (GSK) announced the results from the clinical trial assessing Pandemrix, GSK’s adjuvanted H1N1 pandemic influenza vaccine, administered at the same time as the annual seasonal influenza vaccine, Fluarix. The trial showed that co-administration of one dose of both vaccines in separate arms, induced a strong response in adults for both the H1N1 pandemic vaccine as well as the seasonal vaccine. The trial involves 168 adults aged over 60 years of age, and was designed to evaluate the tolerability and immunogenicity of the co-administration of Pandemrix and Fluarix.

The data from this study confirm previously reported results in an elderly population, which showed that the immune response elicited by Pandemrix exceeded the immunogenicity criteria as defined by international licensing authorities for a pandemic influenza vaccine. Additionally the subjects in this trial also demonstrated a strong immune response to the seasonal influenza vaccine, again exceeding the three immunogenicity criteria as defined by international licensing authorities for a seasonal trivalent vaccine.

"These results provide key information to public health organisations. These new data on the co-administration of both the seasonal and pandemic influenza vaccines could help simplify the influenza vaccination programmes that countries are now starting to initiate,” said Jean Stéphenne, president of GSK Biologicals. “This provides the valuable insight into vaccination in this specific age group that generally benefits from the annual seasonal vaccination.”

In this trial, 89.3 per cent of the subjects receiving both vaccines at the same time demonstrated a response for the H1N1 virus that was above the regulatory threshold of 1:40 seroprotection, which is considered indicative of protection. The immune response for the seasonal vaccine exceeded the regulatory threshold defined by international licensing authorities for registration of the seasonal influenza vaccine each year (69.0%, 78.6% and 100% for A/Brisbane (H1N1), A/Uruguay (H3N2) and B/Brisbane respectively). The annual seasonal influenza vaccine contains 3 strains of influenza identified by public health organisations in advance of an upcoming influenza season. For the Northern Hemisphere 2009 / 2010 influenza season the composition of the seasonal influenza vaccine was determined before the appearance of the pandemic H1N1 strain.

The tolerability of the vaccine in this study was shown to be in line with that observed in the previously EMEA approved H5N1 adjuvanted vaccine as well as in the pandemic H1N1 trials to date. Local reactions such as pain, redness, and swelling at the site of injection were observed in this trial. General reactions such as fatigue, low grade fever, headache, and muscle ache were also observed in this trial, and were similar between the group that received both vaccines at the same time to those in a comparison group receiving the adjuvanted pandemic influenza vaccine with co-administration of a placebo injection.