It´s only a matter of time before another deadly flu pandemic strikes, an international vaccine expert has warned.

International Vaccine Institute director John Clemens said the world was ill-prepared to cope with a major outbreak of disease - possibly because the manufacture of vaccines is governed by profit.

"We are talking about a killer influenza that would kill probably tens of millions of people," he said.

"We磖e not talking about if, we磖e talking about when."

The US is suffering a shortage of flu vaccines after a British supplier, Chiron Corp, was barred from shipping between 46 million and 48 million doses to the nation because of contamination at its plant.

"The current shortage of vaccine in the United States can be attributed to reliance on too few producers," Clemens said in an exclusive interview with The Associated Press.

"Globally, in terms of vaccine development and production that could respond quickly to a killer influenza pandemic, we磖e inadequately prepared."

Clemens - whose institute has been helping to introduce new vaccines against diarrhoea infections, bacterial meningitis and mosquito-born viral diseases for developing nations since 1999 - warned that similar supply disruptions could hit vaccines against other pandemics.

"Something like 80 per cent of the world´s measles vaccines come from one company in India," Clemens said.

"If that company had a problem like Chiron had, it would be a disaster.

"The vaccines that tend to be most affected ... are the vaccines that are the least profitable and of less interest.

"Maybe it´s a bit risky for a society to rely purely on free market economics to guarantee a stable reliable supply of vaccines."

Last week, scientists reported that, for the first time, malaria vaccines had protected some children in Mozambique. Malaria kills more than a million people a year, 700,000 of them children. The experimental vaccines were made by GlaxoSmithKline.

While most pharmaceutical companies are unwilling to produce drugs that don磘 generate a profit, Clemens said the malaria experiments indicated positive progress.

"It is very unlikely that even a highly effective malaria vaccine can be very profitable," he said.

"Yet GSK, one of the world´s largest multinational producers, is actively involved in the creation of the malaria vaccine."

Clemens said a lack of adequate funding remained one of the biggest obstacles for developing affordable vaccines.

Billions of dollars of donations were a drop in the bucket in coverage of vaccinating children in developing nations, he said.

But hopeful signs were emerging because many developing nations, including India, had started to produce generic drugs.

He said a large number of high quality manufacturers had emerged in developing countries in the last couple of years through partnership with big multinational drug companies.

"It´s a win-win situation through the transfer of technology," Clemens said.

The International Vaccine Institute, which conducts feasibility studies in a number of developing countries and helps them to produce more affordable vaccines, is set to open its $US150 million ($A204 million) headquarters and lab in Seoul next week.

It is largely funded by international donors, including the Bill and Melinda Gates Foundation and the South Korean government.