# 709
Hooray for new math,
New-hoo-hoo-math,
It wont do you a bit of good to review math.
Its so simple,
So very simple,
That only a child can do it!
- Tom Lehrer
When I read statements from officials, pandemic plans, or newspaper articles dealing with a potential pandemic, I immediately begin doing math in my head. Inconsistencies practically jump up at me, and smack me in the face.
It's a curse, really. And it drives me crazy.
You see, the old adage that there are Lies, Damned lies, and Statistics is very true. You can prove nearly any point by using numbers. You just need to use the `right' numbers. The ones that fit your agenda.
Until the next pandemic comes around, we won't know what its impact will be, and so any set of numbers can be `valid'. Dmitri Lvov, of the Moscow Institute of Virology can talk about 1 billion deaths, and the WHO can warn of 2 to 7 million deaths from the same pandemic, and neither can prove the other is wrong.
Small wonder that most people don't pay much attention to the predictions, and warnings. If the experts can't agree on the threat, why bother listening?
How does anyone prepare for an event with such a wide range of forecasts?
It's as if you watched a weather report on one channel that said it would be partly cloudy tomorrow, and switched to another channel which is issuing dire Hurricane Warnings.
Who do you believe?
And it isn't just the potential death toll that is in dispute. Economic impacts, attack rates, hospitalization rates, the number of vaccines we have, or can produce, the number of treatment courses of antivirals we will have available, likely absenteeism rates . . . the list of disputed items is nearly endless.
Some municipalities are actively planning for a 1957-style event, one with a mortality rate of only 1/3rd of 1%. Others are looking at a 1918-level event, with a 2% fatality rate.
In Florida, officials are expecting 10% of those infected to need hospitalization, while in the UK, and many other localities, they are using a 4% figure, or less.
Obviously future historians will get the final say, and a great many people will be proven wrong.
It is difficult to know why some people, and agencies, choose one set of numbers over another. Obviously, no one wants to engender unnecessary fear in the citizenry, but it makes little sense to downplay the effects and keep people from taking the threat seriously.
Sometimes there are political pressures involved, as I suspect was the case this week when Margaret Chan, director of the WHO (World Health Organization) indicated that the world's production capacity for a vaccine could reach 1.5 billion doses a year.
Most experts agree that the world's production capacity for vaccines is 500 million doses a year. Ms. Chan correctly points out that these vaccines are for trivalent inoculations, meaning they contain antigen for 3 strains of flu, and therefore she stated we should be able to produce 3 x's that much vaccine for single strain.
And that sounds pretty good. It isn't enough, but it's better than 500 million doses. It gives hope to developing countries that they might receive some of the limited vaccine production during a pandemic.
But is it realistic?
Can we really produce 1.5 billion inoculations in the first year of a pandemic?
Well, we might. But we'd have to overcome some significant technical problems first.
Vaccines are currently produced from eggs, a technology that goes back over 50 years. There are experimental cellular-based vaccines that someday may provide us with copious amounts of antigen, but right now, they aren't quite ready for prime time.
There is encouraging news on this front, and you can read about it here.
Unlike seasonal flu viruses, the H5N1 virus tends to destroy the eggs in which they are cultured. The yield, per egg, turns out to be about 1/3rd that of a normal virus. In other words, our ability to mass produce antigen for the H5N1 virus is far less than for regular influenza.
If that problem cannot be overcome, we are back to the 500 million monovalent doses.
Adding to the difficulty, it appears that the amount of antigen each inoculation will require may be higher than 15ug used with seasonal flu. The Adventis Vaccine, which the United States has purchased, required two shots, of 90ug of antigen each, to achieve a 45% response rate.
That's 12 times more antigen than a normal flu shot.
Other companies have reported that by using adjuvants, additives that improve the immune response, they have reduced the antigen requirement. Still, most vaccines will require two shots, 30 days apart to confer immunity.
So, in order to provide immunizations to 1.5 billion people, as Ms. Chan suggests is possible, we'd have to :
- Solve the antigen/egg yield problem
- Reduce the amount of antigen needed to 15ug per shot
- Need only 1 shot per person
Yes, I know. Pesky technical details that get in the way of a feel-good message. Like I said, math skills can be a curse.
Now perhaps scientists will solve these problems before the next pandemic, or the new cellular based manufacturing technology will come online. What is impossible today may become possible tomorrow. But for now, there are significant barriers to producing vaccines in the quantities Ms. Chan suggested.
Quite obviously, when reading any prognostications about a potential pandemic, and our ability to combat it, critical thinking skills are required.
And yes, that includes anything I write, too.
I have no crystal ball, no way of knowing what the next pandemic will bring. No one does. We can look at likely scenarios, and base our plans and decisions on those, but that is about all we can do.
Personally, I find the predictions of 1 billion deaths about as unlikely as I do the suggestion that the next pandemic could kill between 2 and 7 million people.
Both are possible, but history tells us that a severe pandemic, such as we saw in 1918, killed roughly 2.5% of the world's population. Fifty million out of a population of 2 billion.
Today, with the world's population sitting at 6.5 billion, that would equate to 160 million deaths.
Some countries would likely be hit harder than others. The United States, in 1918, lost less than 1% of it's population, while in other countries, like India, the virus took a much higher toll.
It would seem prudent to me, based on what we've seen in the past, to prepare for that level of a pandemic. If the next pandemic is less severe, we can thank our lucky stars.
But we know it can be that bad, because it has in the past. Maybe we'll get lucky, and the next pandemic won't be that severe.
But to plan for anything less, is to plan to fail.
Let us not forget that the Levees around New Orleans were designed only for a Category 3 hurricane, and we saw how well that worked out.
And if somehow the next pandemic is worse than 1918?
Well, we'll be in far better shape to deal with it if we prepared for a 1918 level event, than if we'd only prepared for a mild, or modest pandemic.
There are, unfortunately, limits to what we can reasonably prepare for.
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