[OT] Flu shots

[Steven Schveighoffer]

On 1/5/18 9:39 AM, Adam D. Ruppe wrote:
> On Friday, 5 January 2018 at 06:20:54 UTC, Patrick Schluter wrote:
>> The only people I ever saw with a flu (I mean a real influenza) had 
>> all one thing in common: they all had gotten the flu shot.
> 
> That's a case of selection bias: the people who get the shot tend to be 
> those who are already at high risk of getting the flu.

Flu shots are relentlessly promoted, and usually free. People get them 
because they think they should, not necessarily because they are at high 
risk.

> 
> The shots cover common strains - or at least what they think will be 
> common strains - but they don't cover all of them. So consider the math: 
> let's say you judge yourself to have a 20% chance of getting the flu, so 
> you get the shot. It cuts your odds by about 50%... but that still 
> leaves you with a 10% chance of getting one of the other strains.
> 
> The general population, on average, has about a 5% chance of catching 
> the flu... so even with the shot, you, in the very high-risk pool to 
> begin with, are still more likely to get it than the average person, but 
> that doesn't mean the shot was ineffective, and, of course, it certainly 
> doesn't mean the shot CAUSED it.

I don't know what caused it. I'm not at high risk, I never get the flu. 
I only got the shot because I had a baby and my wife cajoled me into it 
(didn't get one for baby #2, and didn't get sick). But my internal bias 
says "it's because I got the stupid shot". Note that I got sick pretty 
much right after the shot.

But there is also selective bias on the other side. If someone gets the 
flu and *hadn't* got a shot, there's a bunch of tut-tutting going on 
around them.

In any case, I still will not get one and probably won't until I'm in a 
nursing home and they make me :)

-Steve