Feb 16, 2007 (CIDRAP News) – The World Health Organization (WHO) today reported "encouraging progress" on development of H5N1 avian influenza vaccines, while cautioning that global capacity to make the vaccines remains very limited.
Following a 2-day meeting of vaccine experts in Geneva, the WHO said new vaccines aimed at various strains of H5N1—considered the likeliest candidate to spark a flu pandemic—look promising.
"For the first time, results presented at the meeting have convincingly demonstrated that vaccination with newly developed avian influenza vaccines can bring about a potentially protective immune response against strains of H5N1 virus found in a variety of geographical locations," the WHO said in a news release.
"Some of the vaccines work with low doses of antigen, which means that significantly more vaccine doses can be available in case of a pandemic," the agency added.
However, the statement continues, "WHO stresses that the world still lacks the manufacturing capacity to meet potential global pandemic influenza vaccine demand as current capacity is estimated at less than 400 million doses per year of trivalent seasonal influenza vaccine." The current world population is more than 6 billion.
Sixteen companies from 10 countries are developing prototype pandemic flu vaccines against H5N1, the WHO said. Five of those companies also are developing vaccines against other avian flu strains, including H9N2, H5N2, and H5N3. More than 40 clinical trials have been completed or are under way, most of them involving healthy adults. But some companies have begun clinical trials in children and the elderly.
So far, all the vaccines were safe and well tolerated in the groups tested, the agency said. Most of the companies are using vaccine strains corresponding to H5N1 viruses provided by WHO collaborating laboratories.
Because pandemic flu viruses are products of constant evolution, no one knows how well any of the prototype vaccines under development would work against a pandemic H5N1 virus, but experts hope that the vaccines would provide some protection. Once a pandemic strain emerges, it is expected to take at least 6 months to produce a vaccine precisely matching it.
Today's statement strikes a different tone from that of a report on flu research released by the WHO last November. That report, based on a meeting of 22 scientists in September, said vaccine developments at that point did not look promising. One problem cited was that H5N1 viruses had branched off into a number of different subgroups, and vaccines that worked well against one subgroup did not work well against others.
The November report also said many fundamental questions about H5N1 vaccines remained to be answered. Because of the many unknowns, the report cautioned governments against stockpiling pre-pandemic vaccines. Today's brief statement does not mention stockpiling.
The WHO meeting drew more than 100 flu vaccine experts, who heard and discussed information on more than 20 projects. The aim was to review progress in vaccine development and reach a consensus on future priorities. The meeting was the third of its kind in 2 years, the WHO said.
The statement does not give an estimate of how many doses of H5N1 vaccines have been made so far, and further information was not immediately available.
In 2006 the WHO launched its global pandemic influenza action plan, a program expected to cost $10 billion over 10 years, the statement noted. One goal of the plan is to enable developing countries to build their own flu vaccine production facilities.
In launching the program last October, the WHO called for an urgent effort to boost vaccine production capacity and develop better vaccines, while cautioning that it would take 3 to 5 years for the effort to bear fruit.
Feb 16 WHO statement on vaccine development
Nov 2, 2006, CIDRAP News story "WHO report calls H5N1 vaccine stockpiling premature"
Oct 23, 2006, CIDRAP News story "WHO seeks urgent push for pandemic flu vaccines"