Oct 23, 2007 (CIDRAP News) – The World Health Organization (WHO) today estimated that by 2010 the world may be equipped to make enough pandemic influenza vaccine to immunize 4.5 billion people—vastly more than in previous projections, though still well short of the world's population of 6.7 billion.
"Experts now anticipate that global production capacity will rise to 4.5 billion pandemic immunization courses per year in 2010," the WHO said in a statement. By comparison, last spring the WHO and manufacturers estimated that only about 100 million courses of flu vaccine based on the H5N1 avian flu strain "could be produced immediately with standard technology," the statement said.
The new projection assumes that the demand for seasonal flu vaccines will continue to grow, stimulating vaccine producers to add capacity, and that adjuvants will make it possible to use less antigen (active ingredient) per dose of vaccine, stretching the supply. Adjuvants are chemicals included in some vaccines to provide a general stimulus to the immune system.
"With influenza vaccine production capacity on the rise, we are beginning to be in a much better position vis-à-vis the threat of an influenza pandemic," Dr. Marie-Paule Kieny, director of the WHO's Initiative for Vaccine Research, said in the WHO statement. "However, although this is significant progress, it is still far from the 6.7 billion immunization courses that would be needed in a six-month period to protect the whole world."
Manufacturers this year have increased production capacity for trivalent (targeting three viral strains) seasonal flu vaccine to 565 million doses, compared with 350 million last year, the WHO said, citing the International Federation of Pharmaceutical Manufacturers and Associations. Experts in the field predict that the seasonal flu vaccine production capacity will rise to 1 billion doses in 2010, "provided corresponding demand exists," the WHO says.
"This would help manufacturers to be able to deliver around 4.5 billion pandemic influenza vaccine courses because a pandemic vaccine would need about eight times less antigen, the substance that stimulates an immune response," the statement continued.
Noting that production capacity depends on how much antigen is required for each dose, the agency added, "Scientists have recently discovered they can reduce the amount of antigen used to produce pandemic influenza vaccine by using water-in-oil substances that enhance the immune response."
The statement apparently refers to adjuvants like that of vaccine producer GlaxoSmithKline (GSK). In August GSK reported good results in a clinical trial of an H5N1 flu vaccine containing a proprietary oil-in-water adjuvant. The adjuvanted vaccine induced an acceptable immune response in amounts as low as two 3.8-microgram doses, or about half the 15-mcg dose used for each viral strain in seasonal flu vaccines.
The WHO said the progress in production capacity was reported Oct 19 at a meeting of the agency's Global Action Advisory Group on pandemic vaccine production and supply, an independent 10-member committee.
The new WHO projections were greeted with skepticism by some experts.
"It's a bit breathtaking, this projected increase, and as I read it, it is a really best-case scenario," said William Schaffner, MD, professor of medicine at Vanderbilt University and a member of the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices.
"I think part of what it requires would be for manufacturers to continue to gin up their capacity based on the acceptance of annual influenza immunization," he added. "If the world doesn't continue to use annual vaccine in an increasing fashion, the capacity won't be there to produce pandemic vaccine, should it be necessary."
Influenza and the flu vaccine supply "are both known for their surprises. So we'll take this with a grain of salt, perhaps," Schaffner said. He added that the optimistic forecast makes him "feel good, but I won't hold them to the last dose of the 4.5 billion."
Michael T. Osterholm, PhD, MPH, was more critical, calling the WHO projection unrealistic.
"What the WHO is trying to do is have industry not be industry," said Osterholm, director of the University of Minnesota Center for Infectious Disease Research and Policy, publisher of CIDRAP News. "In a free market industry, there is no way they're going to pick up the cost of all this surge capacity, only to be used very rarely, if ever."
"We need international governments to support this surge capacity, or it's not going to happen," he added. "And putting out these kinds of plans is really nothing more than a distraction. I think this is unfortunate and does nothing to really further the overall preparedness worldwide."
Osterholm also said it's unrealistic to expect the demand for seasonal flu shots to grow at the pace implied by the WHO projections. Noting that fewer than half of US healthcare workers get a flu shot each year, he said, "As far as trying to get that many doses of vaccine into people, it's so unrealistic as to be almost a fairy tale."
Oct 23 WHO news release
May 10 CIDRAP News story "WHO equivocal on prepandemic use of H5N1 vaccines"