GSK bird flu vaccine shows broad cross protection

Sun Mar 2, 2008 9:35am IST

By Tan Ee Lyn

HONG KONG (Reuters) - A vaccine designed by

GlaxoSmithKline to protect people against the H5N1 bird flu may be effective in warding off a few different sub-types of the virus, the company said on Sunday.

In an Asian clinical trial involving 1,206 adults in Hong

Kong, Singapore, Taiwan and Thailand, the vaccine produced antibodies that not only neutralized the H5N1 virus found in Vietnam, but also the variant now dogging Indonesia.

"The vaccine was made using the Vietnam strain. In principle, there is a very broad antibody reactivity that's being induced. These are neutralizing antibodies and they do correlate with protection," Albert Osterhaus, head of virology at the Erasmus Medical Centre in the Netherlands, told Reuters when asked for comments about the study.

Osterhaus was not involved in the study, but is familiar with the results and methodology.

An earlier GSK study in Europe showed the vaccine to be effective in protecting against two other H5N1 subtypes, in China's central eastern province of Anhui and Turkey.

For years now, experts have warned a flu pandemic was long overdue and many have held up the H5N1 virus as a prime candidate because people have no immunity against this bird virus, and because of the high mortality rate associated with it so far.

The virus has infected 368 people in 14 countries since 2003 and killed 234 of them, or 64 percent.

An eventual vaccine to protect people against a flu pandemic can only be made 4-6 months after the start of such a disaster, when the culprit virus strain has been identified.

But human populations still need some form of protection in those initial months of a pandemic and drug companies are in a race to design what are known as "prepandemic" vaccines.

GSK's prepandemic vaccine uses a very low dose, 3.8 micrograms, of antigen. Antigens are substances like toxins, viruses and bacteria that stimulate the production of antibodies when introduced into the body.

But they can be difficult to culture and scientists have been trying to fix that by using boosters, or adjuvants.

Volunteers in the GSK trial received two shots of the adjuvanted vaccine 21 days apart, and blood tests done three weeks after the second shot showed the presence of antibodies which neutralized the Vietnam and Indonesian H5N1 strains.

Osterhaus, however, voiced a note of caution -- that the pandemic may be triggered by a completely different virus.

"We are all scared of H5, but we should realize that other (viruses) are also a threat and the thing with flu is we have to expect the unexpected," he said.

"Separate stockpiling of antigen and adjuvant, that is quite an interesting option," he added.

With such a plan, adjuvants will then be mixed with the antigen of whatever virus emerges as the pandemic strain.

(Editing by Jerry Norton)

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