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GSK's pre-pandemic vaccine protective against bird flu strains

GlaxoSmithKline (GSK), has published clinical trial data from two studies, which support claims that its candidate pre-pandemic, split, low-level antigen vaccine provides a substantial level of cross-immunity against different strains of the bird flu virus, H5N1...

UK pharmaceutical company, GlaxoSmithKline (GSK), has published clinical trial data from two studies, which support claims that its candidate pre-pandemic, split, low-level antigen vaccine provides a substantial level of cross-immunity against different strains of the bird flu virus, H5N1.

The vaccine, which was formulated with GSK's proprietary adjuvant system, is designed to boost the immune response against variants of the H5N1 strain and thus protect the vaccinated population in the event of an H5N1 human pandemic, should the virus mutate sufficiently to become transmissible between humans.

Positive results
Data from the first study, which was presented at the Ninth International Symposium on Respiratory Viral Infections (ISRVI), showed that GSK's pre-pandemic vaccine elicited a strong cross-immune neutralising antibody response in humans against the Indonesian strain of H5N1.

The antibody sero-conversion (when antibodies against the virus appear in the body) factor at day 42 was 25 times greater in the vaccine with the adjuvant system, compared with that observed in the control group immunised with a non-adjuvanted vaccine (77.1 per cent, compared with less than three per cent). The results showing sero-conversion after vaccination only three weeks apart could increase vaccine manufacturing capacity by a factor of ten, say GSK. The vaccine also demonstrated an acceptable safety profile when compared with the control, with injection site tenderness caused by the adjuvant system.

Data from a second study presented at ISRVI showed that GSK's adjuvanted pre-pandemic vaccine could protect against two diverse H5N1 flu strains, again at very low levels of antigen. The in vivo data from the pre-clinical studies showed that the adjuvanted vaccine, which contained the Vietnam H5N1 strain, was not only able to protect against challenge with the vaccine virus strain, but could also provide 96 per cent cross-protection against a lethal challenge with the drifted Indonesia strain of H5N1. The results may give an additional boost to hopes that pre-pandemic vaccination is a viable strategy for inclusion in pandemic preparedness plans.

Jean Stephenne, president of GSK's vaccine division, said: "I am extremely encouraged by the new trial data that has been reported today on GSK's candidate pre-pandemic influenza vaccine. The data confirm that our pre-pandemic influenza vaccine has the ability to recognize and kill an H5N1 strain that is different to the one contained in the vaccine. This means that proactive administration of our pre-pandemic vaccine before or just after the start of the pandemic could help to substantially slow down the spread of disease."

Difficult to predict
Pandemic influenza from a mutated strain of bird flu is considered a serious global health threat. Although the exact strain which may eventually be responsible for an influenza pandemic cannot be accurately predicted, it is believed that the avian H5N1 strain, now endemic in many bird species across the world, is the most likely candidate to mutate first.

David Stout, president of GSK Pharmaceuticals, added: "We believe this vaccine will provide governments with a new option to help protect their populations against the threat of a future human influenza pandemic."

Influenza is a highly infectious disease which globally infects 10-20% of the population every year causing up to 500,000 deaths. Although all persons are at risk, the elderly and the young are the most vulnerable. For decades, trivalent prophylactic vaccines produced in chicken eggs have been used to reduce the burden of influenza with approximately 300 million doses produced globally.

Governments versus pharma
In February 2007, GSK was embroiled in a row with the Indonesian Government, which the company claimed was refusing to supply bird flu samples used in the development of a human vaccine. At the time, Indonesian officials said that they would stop sharing strains of the H5N1 virus with foreign scientists, if the World Health Organisation could not guarantee they would not be used for commercial gain.

The Indonesian government claimed that the system, in which samples are given to the WHO, which in turn supplies them to vaccine manufacturers, allows wealthy Western drug companies to use them to produce vaccines that developing countries cannot afford. GSK, whose vaccine business had global sales of GBP 1.7 billion in FY06, insisted that its vaccines would be available to any country that needed them in the event of a pandemic.

GSK's main competitors in the H5N1 vaccine arena are Baxter Vaccines, a division of the American company Baxter International; Sanofi Pasteur, the vaccine arm of the French pharmaceutical firm, sanofi-aventis; and Chiron, the vaccine business of Swiss pharmaceuticals group, Novartis.

High riskÖ
The development of a bird flu vaccine is a high risk venture, however, as it remains uncertain that a market for the disease will ever materialise. For example, fears that SARS (Severe Acute Respiratory Syndrome) would turn into an epidemic were not borne out. Besides, vaccines are generally considered high risk, because the margins to be gleaned from them are low and litigation activity over side-effects can be high.

Presently, vaccines businesses are looking to government to share more of the related risk In the US, for example, a Biomedical Advanced Research and Development Agency (BARDA) has been proposed and would be exempt from the open records and meetings laws that most government departments must follow. Here, government would act as a partner and provide safeguards and incentives to keep the private sector on board.

7th March 2007

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