Development of swine flu vaccine is "on track" and some countries may begin administering the vaccine as early as September, the head of the World Health Organization's initiative for vaccine research said Thursday.
Dr. Marie-Paule Kieny said manufacturers have made small batches of the pandemic vaccine and are starting clinical trials to determine that the vaccine is safe and produces a protective response.
Dr. Kieny said clinical trials are already started in Australia, China, the United States, Germany and Britain and more will come on line in coming days.
Dr. Kieny declined to offer an updated prediction of how much swine flu vaccine will be available, saying at this point too much is unknown. Earlier the WHO had estimated that in a best case scenario, as many as 94 million doses a week could roll off production lines when manufacturing plants are fully engaged in making the vaccine.
"I would really like to avoid to make any projection right now," Dr. Kieny said, noting that initially the vaccine yield manufacturers were getting was substantially lower than they get when they make seasonal flu vaccine.
A new, better yielding seed strain has been developed, and shipping to manufacturers started Wednesday. The lab that made it, Britain's National Institute for Biological Standards and Control, says the new seed strain produces a yield on a par with that of seasonal flu vaccine production.
That will have to be confirmed by the manufacturers before revised production estimates could be calculated, Dr. Kieny suggested. "We need to see what are the real yields."
As well, she said, results from early clinical trials that show what dose size and number of doses each person needs will allow the WHO to make a better estimate of how much vaccine will be available.
It's one thing to have batches of vaccine made and another to be able to administer the product to people, Dr. Kieny warned, saying regulatory agencies in various countries must first license the vaccines.
Dr. Kieny gave a rundown of the fast-tracking systems various regulatory agencies have put in place, systems that have been devised in recent years in response to the realization that regulators would need to move swiftly when a pandemic starts.
She stressed that the fast-tracking won't undermine the safety of the vaccines being produced.
But countries using vaccine will need to be vigilant to look for and investigate any reports of adverse events linked to receipt of the vaccine, Dr. Kieny said.
The WHO realizes some such reports are inevitable. And while some may be real, others could be what are known as temporal associations - problems that seem like they may have been caused by the vaccine because they occurred after the person got a flu shot but which in reality would have happened regardless.
Dr. Kieny said countries will need to rapidly investigate any signals of problems related to the vaccine and communicate any findings quickly to the public.