Low dose bird flu shot promises pandemic protection

18/09/2007 - A new H5N1 pandemic flu vaccine developed by Sanofi Pasteur could make all the difference in pandemic stockpiling, the new super low dose shot stimulating high immune response in trial subjects.
Sanofi Pasteur''s formulation, which could have less than one tenth of the antigen content found in traditional seasonal flu vaccines, could have prove a real help in terms of dose-sparing and stockpiling strategies in the face of a pandemic threat.
The company used a proprietary novel adjuvant to enhance the immune response to its investigational H5N1 pandemic flu vaccine, which significantly reduced the amount of antigen required in each dose while still stimulating a good response in patients.
Vaccine containing only 1.9ug of antigen stimulated a "high level" of seroprotective immune response in over 70 per cent of the adults on the trial, with a higher dose of 3.75ug generating a high immune response in over 80 per cent of trial subjects.
This is particularly noteworthy when one considers the fact that traditional seasonal flu vaccines (which admittedly comprise three virus strains) contain nearer 45ug of antigen.
Sanofi has used its proprietary emulsion-based adjuvant to boost the immune response of patients treated with the vaccine, which has allowed the vast reduction in antigen content in each dose of vaccine.
The adjuvant was developed by Sanofi in-house specifically for the pandemic and pre-pandemic setting, according to a spokesperson for the company. Although it could feasibly be applied to other vaccine products, the priority for now is to develop a vaccine for pandemic stockpiling, in-PharmaTechnologist.com was told.
Subjects in the vaccine trial received two doses of vaccine, with four levels of antigen dose tested in all. As well as the enhanced immune response, Sanofi also reported that preliminary data showed good cross-reactivity to a more recently circulating H5N1 strain, with assessment of this feature of the vaccine currently ongoing.
Sanofi Pasteur is the current global leader in vaccine manufacturing capacity, in 2006 producing 170 million doses of seasonal flu vaccine - over 40 per cent of global capacity.
However, with the vastly reduced antigen content of the adjuvanted H5N1 vaccine, Sanofi believes that it has the potential to provide "billions" of doses of vaccine from its manufacturing sites in Pennsylvania in the US and Val de Reuil in France where the vaccine will be manufactured.
Sanofi is hailing the investigational vaccine as "a significant achievement for public health and a breakthrough in research and development of pre-pandemic and pandemic vaccines," and is keen to move on with development following the successful trial results.
"Having now demonstrated the potency of the adjuvant, we take that as the green light to continue development of the vaccine," a spokesperson for the company said.
The results announced today followed completion of Phase Ib trials, with clinical trials in the US planned for early next year, along with an expanded EU trial.
As to when the vaccine might eventually make it to market, Sanofi is reluctant to pin down a solid time frame.
"Obviously the objective is to develop the vaccine as quickly as possible," a spokesperson for the company said.
"But we should use the time while we are not in a pandemic situation to fully develop the vaccine. Plans could always be accelerated according to government requirements."