(2017-12-18, 11:30 PM)fls Wrote: [ -> ]Pretty much (for your purposes, anyway).
This is why everyone says that you're a smug know-nothing asshole. Why not just say "yes"? Why do you feel the need to add "for your purposes, anyway"... as if I'm being disingenuous or twisting something... as if there is any room for debate about this point and you'll condescend to humor me.
Asshole.
The CDC's yearly vaccine effectiveness studies are test-negative case-control studies. Agree? (hint: "YES" is the correct answer)
Quote:No, odds ratios don't depend on the underlying incidence... No, again, the underlying prevalence of ILI and propensity to seek medical care do not alter the equation.
You're completely wrong.
Although I can't find it at the moment, one of the CDC's presentations of their study noted the underlying assumptions. And a quick google search can find many study authors mentioning the fact that this test-negative case-control methodology relies on these assumptions. Here is just one I found within 5 seconds:
https://www.ncbi.nlm.nih.gov/pubmed/23499601
"With the assumptions that (a) the distribution of non-influenza causes of ARI does not vary by influenza vaccination status, and (b) VE does not vary by health care-seeking behavior, the VE estimate from the sample can generalized to the full source population..."
"The cost of the test-negative design is the additional, difficult-to-test assumptions that incidence of non-influenza respiratory infections is similar between vaccinated and unvaccinated groups within any stratum of care-seeking behavior, and that influenza VE does not vary across care-seeking strata."
Quote:I'm not sure what you were going for with this.
I provided an example case where these assumptions are bad and the test-negative case-control study would show high VE even if practically the only people getting sick are vaccinated.
Quote:Quote:Isn't it true VE is not the only statistic needed to gauge flu vaccine benefit?
Yes. That's why there are many different studies done to gauge benefit (and risk).
VE means nothing without knowing the risk of getting the flu while unvaccinated. So a person would need to know the likely infection rate in their group in order for VE to provide any measure of benefit.
Let me explain this to you again since you can't seem to wrap your mind around it.
If the probability of getting the flu for a healthy 35 year old male is 1 in a trillion and that person takes a vaccine with 50% VE, then he now has a 1 in 2 trillion chance of getting flu. The vaccine provides a negligible benefit.
If the probability of getting the flu for a 75 year old alcoholic is 1 in 2, then 50% VE would lower the probability to 1 in 4 - a substantial benefit.
There is no good data on flu risk and estimates I've seen vary wildly from <1% to 20%. Without good data on unvaccinated risk, VE can tell us nothing about the benefit.
My personal experience is that I've only once in my life had the flu and it was when I was child and it was around the age that I received my one and only flu shot. I rarely ever encounter anyone who has the flu or has had the flu recently. Since there is not really much good data to go on, I'll just go on my personal experience and say that the actual chance of me getting the flu as a healthy person is very very low, so even a high VE would provide me with negligible benefit and it would carry additional risks.
Quote:Quote:Does pro-vaccine propaganda and advertisement make anyone aware that VE % alone means nothing?
I don't know. People seem to follow the advice of their physician and public health advisors, which makes the point moot, I suspect.
Of course you know. You're just being obtuse again. The CDC's VE estimate gets disseminated as the sole number upon which people are supposed to gauge benefit. It gets talked about on TV talk shows and news programs. It is included in flyers and advertisements and employee handouts. But the VE estimate is never accompanied with unvaccinated risk or infection rate which is necessary to gauge benefit.