GlaxoSmithKline (GSK) announced that, approximately half a million people will have received its pandemic H1N1 vaccine, Pandemrix, as part of Government initiated vaccination programmes across Europe, which commenced earlier this month. GSK also announced new results from a clinical trial assessing the use of Pandemrix in adults aged 18 to 85 years of age. The trial, which is ongoing, shows that after the first dose of adjuvanted vaccine, a strong immune response was demonstrated, inclusive of the over 60 age group. The immune response elicited by Pandemrix in all age groups exceeded the immunogenicity criteria as defined by international licensing authorities for a pandemic influenza vaccine. The adjuvanted vaccine in this trial contains the dose of H1N1 antigen (3.75 µg) which is the EMEA approved final formulation.

"These results complete GSK’s first line results across key age groups. As previously shown in young children and adults under 60 years of age, these new data demonstrate the ability of the vaccine to induce a high immune response considered indicative of protection after one dose across a wide range of ages, including the elderly.” said Jéan Stephenne, president of GSK Biologicals. “These data are very important for those in government who need to continually assess new data in light of the current global public health challenge.”

The trial, which is taking place in Belgium, involves 240 adults aged 18 to 85 years, and was designed to evaluate the tolerability and immunogenicity of Pandemrix. Half of the subjects enrolled in the trial (120 subjects) were under 60 and the other half were over 60 years of age. A planned analysis was performed 21 days after the first dose, immediately prior to administration of the second dose.

These results show that 88.0 per cent of the subjects between 61 to 70 years of age, and 86.7 per cent of those over 70 years of age, demonstrated a response that was above the regulatory threshold of 1:40 seroprotection, which is considered indicative of protection. Results in the age group 18 to 60 years of age were similar to previously reported studies in that age group, with 97.5 per cent of subjects reaching the 1:40 seroprotection level in this trial.

The tolerability of the vaccine in this study was shown to be similar to that observed in the previously EMEA approved H5N1 adjuvanted vaccine. Local reactions such as pain, redness, and swelling at the site of injection were observed, but no severe reactions were reported to date. General reactions such as low grade fever, headache, and muscle ache were also observed, and were in line, or slightly more often than observed with GSK’s current unadjuvanted seasonal influenza vaccines. Regulatory authorities will review these data and then may consider changes to the label, which currently indicates a two dose schedule for all age groups.