Human trials of bird flu vaccine start

Pharmaceuticals giant GlaxoSmith-Kline has started new human trials in the hunt for an effective vaccine to ward off deadly bird flu and says it believes the injections could help protect against a future global flu epidemic.

A range of large drug companies is developing a human vaccine for use against the H5N1 virus that has killed 127 people since late in 2003 and killed or led to the culling of millions of birds.

The plan is to provide some degree of protection before a pandemic - if one begins - then modify the vaccine to more closely match the pandemic virus, which will be a new genetic variant.

There is no clear evidence H5N1 can be spread easily among people, although family members have been infected.

Health authorities fear it could mutate into an easily transmissible human virus, causing a pandemic that kills millions.

Anti-viral drugs such as Tamiflu - which are not vaccines - are considered the best initial protection against a pandemic of a new flu virus.

The New Zealand Government has spent $26 million building a stockpile of enough Tamiflu to treat a fifth of the population. It has also negotiated a deal with Melbourne-based vaccine maker CSL to supply vaccine against pandemic influenza, but it would not be available for 15 to 27 weeks after the World Health Organisation declared a pandemic and New Zealand placed its order.

GSK said it had started a clinical trial of an H5N1 vaccine in Germany and was running another in Belgium in which the vaccine had a new type of adjuvant - chemicals used to enhance the immune system response.

Results of the safety and immune-response trials are expected within three months and the company hopes to have the vaccine in production by year's end.

CSL's director of public affairs, Rachel David, said a clinical trial of her company's prototype vaccine showed it produced a "reasonably good" immune response. CSL was now recruiting participants for a further trial.

"Over 50 per cent got a good immune response, which is okay, given that people have not been exposed to the antigen before," she said.

GSK's head of flu operations, Emmanuel Hanon, said the company believed that vaccination with an appropriate H5N1 vaccine would help "educate" the immune system, reducing the toll associated with a pandemic.

"This means that if the current bird flu virus mutates to allow human-to-human transmission, a vaccinated person will be better prepared to combat the H5N1 pandemic flu virus," he said.

Virologist Professor Bill Rawlinson, of Prince of Wales Hospital, Sydney, said observational studies suggested repeated vaccination against flu raised the body's ability to ward off even flu strains not covered by the vaccine.

People repeatedly vaccinated suffered less sickness and their death rates were lower than those injected with the vaccine for the first time.

Repeated use of this vaccine might conceivably even confer some protection against a pandemic mutation of H5N1, although that was "a plausible guess".

Professor Rawlinson said making an H5N1 vaccine in the traditional way, using eggs, was proving difficult because the virus killed poultry.