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| Baxter develops bird flu vaccine |
| 28-JUN-2008 Intellasia | Praguepost |
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| 28 Jun, 2008 - 7:00:00 AM |
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The solution to a potential avian flu pandemic can be found approximately 30 kilometres outside of Prague, in Bohumile.
A production facility there owned by the US biotech firm Baxter International is producing a vaccine, Celvapan, which has found success by deviating from the norm. To create the vaccine, Baxter's scientists used monkey cells, rather than the traditional method of using hen's eggs.
The advantage is in the consistency and high output of the cells. Hen's eggs can cause logistical difficulties, requiring lots of advance planning. And during an epidemic, the birds would be at the mercy of the very same disease that the vaccine aims to combat.
"What we saw in Hong Kong was large-scale culling of birds [during outbreaks], so of course the supply of eggs becomes a concern," said Hartmut Ehrlich, vice president for global research and development for Baxter Bioscience.
Erlich, along with Markus Müller, coauthored a paper on the vaccine's trials that appeared in the June 12 edition of the New England Journal of Medicine, one of the world's most prominent medical journals. The vaccine recently completed its phase I/II safety trial, which involved 250 people. The article reported a strong immune response in subjects who received the vaccine twice.
In addition to its culture method, the vaccine also makes no use of adjuvants, a component of most vaccines that boosts immune response but also causes many side effects.
Celvapan targets divergent strains of H5N1 virus, the flu that first passed to humans in Hong Kong a decade ago, killing six people. According to the World Health Organisation (WHO), the avian flu has killed 241 of 383 cases since the Hong Kong outbreak, giving it a 63% fatality rate.
While the flu has presented itself primarily in Southeast Asia, there is global concern of a pandemic should the virus mutate, allowing it to transmit from human to human more easily.
"If you speak to experts within the WHO or within the ministries of health of various countries, there's a lot of concern in this direction, and that's why some countries have already decided to buy the vaccine directly from us or buy manufacturing capacity for them in the case of a pandemic," Ehrlich said.
The United Kingdom has already been one such country to purchase the vaccine, and Ehrlich said the Czech government has been in talks with Baxter as well.
While the last flu season didn't show the sort of outbreaks that have worried health officials in the past, it is impossible to predict whether the virus will mutate into a more virulent form in the future, Ehrlich said.
"Last winter we didn't see birds containing the virus falling from the sky, but the virus is still incubating in Southeast Asia," he said. "It hasn't happened yet, but the fear is that a virus could be generated that jumps easily from human to human. For a pandemic to occur that would need to happen."
The whole virus
Baxter opened its manufacturing operations in Bohumile in 2001 exclusively for the cell-culture production of its avian flu vaccine. The facility, one of the largest cell-culture vaccine production facilities in the world, had an initial investment of US$70 million (1.1 billion Kc) and employs 230 people.
After years of readying the lab, it was licensed to manufacture the vaccine in 2005.
Baxter's cell-culture method, which it is the first to use toward avian flu, has been employed for successful vaccines against other diseases such as polio and rabies. Ehrlich said the method has been developed for nearly 15 years, after a memorandum from the WHO urged researchers to pursue it.
The vaccine's production time, a key part in preventing epidemics, is cut nearly in half with the cell-culture method, from 2228 weeks using eggs to 12 weeks with cell cultures.
The process using hen's eggs also has a different effect on the immune system because of how it is manufactured. The virus in the hen's egg is treated with bleach and delivers a "disrupted" version of the virus.
The cell method delivers a "whole" version of the virus, and at a much lower dose. Because the immune system encounters the full version of the virus, it has an enhanced response. The added benefit of the method has meant that Celvapan worked against four different strains of the virus, whereas a hen's egg vaccine would be limited only to the infecting strain.
Baxter's next step has been a phase III study with 550 subjects, the data from which has not been fully analysed yet. The results of all three studies are being process edfor an application for licensure from the European Medicines Agency, which Ehrlich expects to be approved this fall.
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