#754
A number of countries are aggressively working towards acquiring a pre-pandemic H5N1 vaccine, with the notion of inoculating their population before a pandemic strikes.
Worries over how well any vaccine made today will match a pandemic virus, however, has stopped the WHO (World Health Organization) short of endorsing such plans.
This from CIDRAP (Center for Infectious Disease Research & Policy).
WHO equivocal on prepandemic use of H5N1 vaccines
May 10, 2007 (CIDRAP News) – The World Health Organization (WHO) said yesterday that "a number" of human vaccines against the H5N1 avian influenza may become available soon, but declined to say whether they should be used before a flu pandemic arises.
Besides the H5N1 vaccine approved by the US Food and Drug Administration in April, "a number of the most advanced candidate vaccines against H5N1 avian influenza might be registered within six months to two years," the WHO said in a question-and-answer bulletin on pandemic flu vaccines.
Vaccine developers are focusing on H5N1 because it is regarded as the virus most likely to evolve into a pandemic strain. But if it does, no one knows how much protection will be provided by vaccines based on current strains.
As they become available, "prepandemic" vaccines for H5N1 could be used in poultry workers, healthcare workers, or even whole populations, the WHO said, but the agency stopped short of recommending that step in advance of an actual pandemic.
"WHO's expert groups point out that the pandemic virus may be quite different than what people are immunized against and therefore the vaccine may not be protective, and that any decision about whether to use avian flu vaccines as a hedge against pandemic influenza must be done so with full knowledge of this fundamental uncertainty," the statement said.
"In the best scenario, such use of a vaccine would prove life saving," it continued. "In the worst, it would only have little effectiveness, and some experts consider such a use of the vaccine as an unfounded expenditure. WHO continues to review all of the scientific, health and social benefits and drawbacks with its experts and policies are regularly updated."
Once a flu pandemic virus is identified, it will take at least 4 to 6 months to produce the first doses of vaccine for it, the WHO said. Other predictions about the time needed to develop and start producing a pandemic vaccine have typically said at least 6 months.
In other comments, the WHO said a rapid increase in flu vaccine production capacity is likely in the next few years but cautioned that a universal flu vaccine may be more than a decade away.
The statement said drug companies are moving to increase vaccine production capacity "substantially," and capacity could "nearly double" by 2009. Current world capacity has been estimated at about 350 million doses of seasonal vaccine, with each dose targeting three flu strains.
In the next 3 to 5 years, the WHO said, "We will see movement towards increased vaccine production capacity in both industrialized and developing countries with a combined vaccine production capacity potentially above 3 billion doses per year." The current world population is more than 6 billion.
There is hope that a pre-pandemic vaccine, even a poorly matched one, might provide some level of protection against the H5N1 virus; that it might not prevent infection, but that it might reduce mortality.
There are also concerns that once a pandemic is underway, the logistics of dispensing a vaccine becomes much more difficult. Ideally, you'd rather inoculate the population before the virus erupts.
The WHO also stated, again, that the delay in creating the first doses of a vaccine would be substantial. This from the WHO Q&A on pandemic vaccines.
How long will it take to produce the first doses of pandemic influenza vaccine in the event of a pandemic?
If production of a vaccine starts on the day a pandemic is declared, it is thought that at least four to six months will be necessary to produce the first doses of vaccine.
Using currently available technology, should a pandemic erupt anytime soon, and should it last 18 months, it would be over before enough vaccine could be produced to inoculate more than about 10% to 15% of the world's population.
The Holy Grail of vaccine researchers is a universal influenza vaccine, one that would work across all strains. And that would be a huge step forward in our battle against influenza. But it wouldn't completely solve the problem.
Vaccines generally produce short-lived protection, and usually begin to lose their effectiveness after about 6 months. A universal vaccine would likely require booster shots every year or two in order to remain effective.
Even with a universal vaccine, we'd still face the problem of producing and dispensing enough for a world with more than 6 billion people. The advantage would be, we could begin inoculating people before we knew which strain was about to emerge.
And that would be a sizeable advantage over where we are today.
Post a Comment