GSK Corporate HQ, Brentford, Middlesex, UK

GlaxoSmithKline (GSK), the UK pharmaceutical giant, on Monday announced that simultaneous vaccination against seasonal and pandemic flu provides protection against the virus without provoking significant side effects.

The results from the clinical trial assessing Pandemrix, GSK’s H1N1 pandemic flu vaccine, administered at the same time as the annual seasonal flu vaccine, Fluarix, 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.”

Reports from Canada had suggested that one vaccine could negate the effects of the other but no scientific data has been published.

In the GSK trial, 89.3% of the subjects receiving both vaccines at the same time demonstrated a response for the H1N1 virus that was above a regulatory threshold, 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 flu vaccine each year.

GSK said the annual seasonal flu vaccine contains 3 strains of flu identified by public health organisations in advance of an upcoming flu season. For the Northern Hemisphere 2009 / 2010 flu season the composition of the seasonal flu vaccine was determined before the appearance of the pandemic H1N1 strain.  

GSK said 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 pandemic flu vaccine with co-administration of a placebo injection.

France currently recommends giving seasonal and pandemic vaccines, but with a three week interval, which creates a big burden for the health system.