The length of a future dangerous influenza pandemic will be determned by the speed at which vaccines can be produced against the specific flu strain that emerges. For something like the H5N1 avian or bird flu speculative production of vaccines ahead of time might not help much because the bird flu virus is mutating a fair amount. Though vaccination against current strains would probably at least provide some degree of partial immunity and probably deserves more consideration than it is currently getting.
I'm going to start collecting information about vaccine production capacities around the world since those capacities will determine the length of a pandemic and therefore the number of lives lost and the size of the economic cost. Here's the first vaccine production capacity report I've found. Hungary could make a half million vaccine doses per week.
If a different strain of the virus becomes dangerous for humans, it would take Hungary eight weeks to produce the first 500,000 vaccines after receiving the virus from the WHO, and it could then make another half a million portions per week.
That puts their yearly capacity at about 25 million. One wonders how much they could scale up production during an emergency and how long the scaling up would take to implement.
I'd like to know whether the Hungarians are using a new type of vaccine production technology. The bulk of flu vaccine production today is done using fertilized chicken eggs and takes months. Are the Hungarians saying they can produce a half million doses each week? Or are they saying they can put a half million doses worth of fertilized chicken eggs into the process each week with the results coming out two or three or four months later?
I'd also like to know whether the report from Hungary assumes a vaccine dose size based on the newness of H5N1 in humans. A completely new strain of influenza requires a larger vaccine dose. I've previously read that new strains require double the dose and hence all influenza vaccine production capacity figures have to be reduced by a factor of 2 when discussing bird flu. Chris Spence, who writes an avian flu blog showed up on in the comments of one of my previous posts and painted an even bleaker picture of the dose size needed to handle H5N1 bird flu in humans.
The story with vaccine development is even worse. The current vaccine being tested and developed and in the U.S. based on the avian version of the virus (avian -> human, rather than human -> human) requires a very large dosage rate to create an immune response. Based on early testing, to create an immune response, a dosage had to be given of 90uL, rather then the normal vaccine level of 15uL. In addition, because we have no natural immunity to this virus, we need to have two vaccines given, a month apart, for a total dosage of 180 uL (90uL X 2). This reflects a total required dosage of 180uL which is 12 times the normal dosage. Unless studies using Adjutives and other methods to reduce the required dosage prove successful, our reported production capacity for flu vaccine in the U.S. of 90 million annual doses, is actually only a capacity of 7.5 million doses (vs a population of roughly 296 million or a 2.5% coverage rate). Add this to the likely low effectiveness of the vaccine (it is being produced based on the current strain directly from birds - the pandemic strain that spreads from humans to humans is likely to be significantly different), the effectiveness of the current vaccine may only be 20 - 40% effective (no one knows until the strain breaks out, but based on prior vaccines that were a poor match to the final virus). The world wide vaccine production capacity is currently 300 million doses, or 25 million at this higher dosage rate. With a world wide population of 6.45 billion. This would only cover 0.4% of the worlds population. Not very encouraging news.
Is the H5N1 vaccine production situation really that bleak?
What vaccine dosage size would be needed in an H5N1 pandemic? Also, are any new vaccine production technologies far enough along to provide hope for more rapid scaling up of vaccine production? Also, how rapidly could conventional influenza vaccine production technology be scaled up?
|Share |||Randall Parker, 2005 September 28 08:17 PM Pandemic Vaccines|