Wednesday, December 2, 2009

Flu Thoughts

Good news, team: this flu season's about to come to an end. Bad news is that the regular flu season is just getting underway.

It is hard to underscore just how much this virus tore through the population. The CDC reports higher-than-normal medical visits for influenza-like symptoms in every region of the country--a total of 51 of 54 epidemiologic jurisdictions. Now it doesn't tell you the total number of cases, which at this point could only be made with a guess as most cases are identified "clinically" and aren't even reported, much less confirmed. There are just too many cases to allow for that kind of precise measurement. However, the CDC's best guess is that, by the end of the epidemic, about 22 million Americans will have been infected. That's simply an awesome number of infections.

If you have gotten the flu thus far, it's overwhelmingly likely that you got the novel H1N1 virus. The CDC data indicates that only four out of nearly 2,500 strains are "seasonal" strains. ("Strains" are the molecular sub-type of the virus...think of different colors and years of Toyota Priuses, with one or two Camrys thrown in, and you've got a rough idea of strain differences.) And some further good news is that these strains remain almost universally sensitive to oseltamivir (Tamiflu). Even better is that this virus so far hasn't become really deadly. Shown below is the graph displaying pneumonia and influenza mortality (link above) and, except for a recent blip, the mortality is well within the expected level during
nearly all of the "Swine Flu" epidemic. The CDC estimates are for a total of 3900 deaths (540 of those occurring in people less than 18 years of age), which is considerably less than the average annual influenza mortality, which tops off at about 40,000. We owe our good fortune to the fact that this flu strain wasn't particularly virulent and thus far hasn't shown any predilection for mutating into a deadlier strain. There was some news coming out of Norway that there was a more virulent strain that had been recovered in two patients who had died and a third who had been critically ill, but subsequent samples from other patients haven't shown the same molecular signature. So, all in all, hard to say what's going on there.

I've heard a lot of concerns from family and friends over the past several months about the safety of the flu vaccines. An amazing 72 percent of Americans are either very or somewhat concerned about the safety of the Swine Flu vaccine. Granted, it has been been confusing, given frequently changing recommendations from the CDC, the shortage of the vaccine, and the generally confusing issue that there are separate vaccines for the seasonal flu strains and the Swine Flu strain. Still, at least two points need to be kept in mind: first is that the technology used to make the flu vaccine hasn't changed in decades; the vaccine for the novel strain is no more "novel" than that of the seasonal strains, it's just that the strain of virus being grown in chick eggs--yes, that's how it's done--is different. The process of manufacture, however, is totally the same. The second point is that it's very safe. Keep in mind that there is the issue of "background noise" when you give out this many vaccinations: if you just watch 10 million people over the span of six weeks, nearly 17,000 women will have miscarriages, about 20 of them will come down with Guillan-Barre Syndrome (a potentially life-threatening condition sometimes associated with vaccines), and half a dozen will experience the joys of sudden death. So that means that you'd expect to see these kinds of numbers following a mass vaccination campaign. If you're trying to understand why you got Guillan-Barre solely from the perspective that you were vaccinated the week before, you can't really know just from your own experience whether the vaccine was the cause; you have to look at the incidence throughout the population. (The failure to grasp this point is what makes the anti-vaccine crowd so exasperating. Statistically, when you give millions of vaccine doses it's bound to happen that some kid is going to get sick after getting the shot...because the kid was going to get sick anyway!) Of the nearly 34 million doses of the Swine Flu vaccine given so far, there have been only 84 reported adverse events associated with the vaccine, including 6 deaths and 4 cases of GBS. That's a pretty good record.

If one must be in the vaccinophobic crowd, then at least pick the right thing over which to have an irrational fear. Like I said, the vaccine that you may or may not have gotten for your kid due to shortages is just an old-fashioned vaccine. You want truly different? The FDA just met and decided against a flu vaccine "manufactured" using caterpillars. The Protein Sciences Corporation in Meridien, CT had their application rejected on a 6-5 vote mainly because the data at this point in time are insufficient. But you can tell by the vote that it's close. Advantages of making flu vaccines in caterpillars? One, people who have egg allergies can be vaccinated, and two, the company claims that because the virus grows faster in caterpillars than in chick embryos it could ramp up production much quicker than in the traditional manner, no small consideration given the profound shortages of vaccine stocks this time around. (And keep in mind that it's still likely an irrational fear.)

My own sense of the mild hysteria surrounding the flu vaccine? An indicator of the extent to which Americans distrust authority. Having grown up with a marginally rebellious attitude in my younger years, I am not completely unsympathetic to the mindset that authority should be questioned (particularly as my high school Principal, Mr. Sertell, was practically begging to have his judgement held up for scrutiny). But there's a difference between a healthy skepticism of official pronouncements (take the President's recent Afghanistan Surge speech as an example) and outright paranoia, and I have the sense that we've been increasingly shifting towards the latter perspective over the past decade.

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