A Cost- Benefit Analysis of Immunizing Healthy Adults Against Influenza

Omitting death seems like a big deal. Very crudely, it looks like p=10^-4. It's said that society values each life at $5M, so that's E=-$500 already, but each individual likely values their own life a bit higher.

having an insurance policy increases the expected value of receiving a flu shot, as many insurance companies will completely cover the cost of receiving a flu shot.

That, and a little pondering why, is all you ever needed to know.

Actually estimating the utility of a vaccine is very difficult for individuals who are not complete shut-ins interacting with nobody (but then those people won't get sick in the first place), or individuals who aren't complete psychopaths without a job or with a job unusually resistant to damage from absence of coworkers (because even a psychopath would generally not want to get the co-workers sick). This is because a vaccine massively affects the ability of the virus to spread to other people, and in the beginning phase of the epidemic one person infects more than other person. It matters a great deal to an insurance company (or a government), so they can invest a lot of man-hours into modelling of the spread of the virus.

It is fortunate that the cost of the vaccine is so low and the illness is so common you arrive at the correct decision regardless.

the costs of providing palliative care to oneself, estimated at 100 USD

I don't think I've ever had flu --- certainly I have never been diagnosed with it --- but when I've had an incapacitating heavy cold, palliative care consists of staying in bed and surviving on half a can of soup a day, and maybe some over-the-counter symptomatic treatment. This agrees with the recommendations for actual flu here and produces a saving of money, not a cost.

In case it was not obvious, the correct takeaway from this article is that you should go and get a flu shot, if you haven't gotten one already this year. If you have already gotten a flu shot this year, and you reply to this comment with a message that states that you have done so, I would be more than happy to upvote you.

Judging by some of the attitudes I have heard from my friends about getting a flu jab (similar to Lumifer's comment), I have found that it is actually more effective to encourage people to get flu jabs for the benefit to others via herd immunity, rather than by emphasising the benefit to them.

I don't know if this is maybe some kind of ego-bias in that healthy people underestimate their chances of getting sick, or that doing something for you doesn't get you fuzzies, whereas doing it to help sick people and babies does.

Of course I am in a country that won't pay for healthy people to get the flu jab, but will pay for their hospital stay if they get sick enough to be hospitalised. The NHS does, however, pay for elderly people and people with most long-term health conditions (including asthma and diabetes) to get the jab.

I imagine that the NHS has done a cost-benefit analysis of the costs to itself to pay for healthy peoples' flu jabs versus their hospital stays if they do get sick, but I don't know if they have.

I'd like to see more analyses like this. Does anyone want to do blood donation?

I think the calculation somewhat under values the cost of being sick. If it's been a while since the last turn you were serriously sick it's easy to forget just how deeply unpleasant it is. I was really sick with food poisoning recently and would have happily paid >500 USD to avoid that. It's been a while since I had the flu, but I think putting the misery and suffering at less than 300 USD is not optimal modeling.

Huh, I'll look into this. At 33yo it never really occurred to me healthy people got flu shots. I have never had a shot or the flu, and the only people I know who have had other contributing weaknesses. I'm not saying I will necessarily get one, but this definitely opens the question for me. Thanks!

That was a very nice article, well-researched and thorough; However, I do think I need to point out that you have made an error in your maths. (Interestingly, the effect of the error was to increase the cost of getting a flu shot).

Specifically, take a look at figure one, at the probabilities. You have stated, earlier, that the flu injection has an efficacy of 60%; that is to say, 60% of people who get the flu shot, who would otherwise have got the flu, don't get the flu.

Given that 90% of people don't get the flu, whether they have the shot or not, this means that the odds of not getting the flu after getting the shot should be 96%, not 94%.

Similarly, the odds of being hospitalised should be 0.0002, not 0.0003; and the odds of getting the flu but not being hospitalised should be 0.398, not 0.597.

In short, your calculations presumed an efficacy of only 40%. (The fact that it was still shown to be worthwhile, with such a low efficacy, is quite telling).

This reduces the expected cost of getting the injection to $71.40.

That minor point aside, thank you very much for doing the research for this article.

Getting complications (allergy, ...) from the flu shot should be included somewhere in the graph - it can't be totally screened away, and while it's unlikely to happen, it's not much more unlikely than dying from the flu.

But most importantly (and this time, arguing for the shot), the "herd immunity" effects should be considered. Even if just half of the people take the shot, those who because of the shot didn't get the disease won't be carriers and won't spread the disease to even those who did get the shot.

I'm not seeing where the probabilities in the decision tree come from. Does 10% of the unvaccinated population catch flu every year, and 6% of the vaccinated? Those seem extraordinarily high figures, and I don't see them in the text. The two figures together imply an efficacy of 40%, not the 60% cited. The connection of the other probabilities to the data is also not clear.

Although the costs of the possible outcomes shown in Figure 1 were calculated under the assumption that the individual receiving the flu shout was uninsured, having an insurance policy greatly increases the expected value of receiving a flu shot, as many insurance companies will completely cover the cost of receiving a flu shot.

You're still paying for the medical care you receive on insurance. You're just paying in advance, at a rate that the insurance company calculates to cover the expected costs, plus their own profits. If the entire population suddenly goes out and gets flu shots this year, that will show up in everyone's premiums down the road. If your employer pays your insurance, you're still paying, in the form of a lower salary. The only people who don't pay medical costs are those on public benefits, whose costs are paid by those not on benefits.

ETA: This applies to nationalised health systems as well. Flu jabs are there paid for by taxes. All these different ways of paying for it may distribute the cost in different ways, but that cost is always paid. If it were not paid, there would be no vaccinations.

ETA2: Likewise sick pay. If your employer guarantees your salary while you're sick, it's at the cost of your salary when you're well. The cost is spread over the whole company, but it is paid. The cost is always paid.

I'd also like to see some sensitivity analysis, given that the $14 benefit derived from the model is a difference between much larger figures, $104 and $90.

I have already gotten a flu shot this year, primarily because the cost of getting one is approximately 10 minutes and 0 USD (They're covered by cost of attendance at my university and in a very convenient location for me).

> The cost of catching the flu despite not receiving a flu shot was estimated as being 1000 USD for a healthy adult, given the cost of losing 4-5 days of productivity if one's time is valued at 20 USD/hour, plus the costs of providing palliative care to oneself, estimated at 100 USD, and the cost equivalent to the negative monetary value of experiencing a lower quality of life than usual while sick, estimated at 200 USD. <<

This is this bit that stands out the most to me as warranting some analysis. Maybe in the US things are very different, but in Australia we have sick leave for the full time employed - which is most people on 20USD/hour (or local equivalent). Being sick for 4-5 would not cost you a penny. Mind you, this may then translate to an argument for employers to provide free flu inoculations as has been advocated elsewhere: http://www.abc.net.au/news/2014-05-05/employers-encouraged-to-provide-flu-vaccinations-for-staff/5431698

I think the analysis changes a lot if you have insurance/live in a country with a public health care system.

Also where did 200 USD for diminished quality of life come from? That phrase has a particular legal meaning - is that intentional, or do you just mean "what I would pay to not have the flu, other economic considerations aside"?

I think there's a pretty big mistake here - the value of not getting flu is a lot more than $200.

At a $5M value of life, each day is worth about $200, so 7 days of almost complete incapacitation is -$1400.

I would certainly pay $1400 upfront to make a bad flu just instantly stop.

What about the cost of pain from the flu shot? Based on my past experiences (all from childhood, so maybe not that accurate for me now), I would be willing to pay $20-$50 to avoid the pain from a shot. I also didn't find the flu that unpleasant, so I might only be willing to pay $120-150 to avoid it assuming no risk of death. It seems like the expected value of a flu shot is small enough for these sorts of subjective preferences to tip the balance in many cases.

Figure 1. Decision Tree for Assessing the Impact of Immunization in Healthy Adults

I'd like to know how elastic the result is for changing cost values. Did you plug in different values and what were the results?

Am I being particularly dense or are there no numbers in the form of "expected value of not getting the shot: $Y", "expected value of getting the short: $X" and "difference $(X-Y), therefore ...."

The costs in your calculations, they are costs for whom?

To make an obvious observation, medical insurance exists for a reason and a lot of people are employed in such a way that missing a week of work does not cost them $1000. Another lot of people isn't employed at all.

Nice sharing thanks

None of the meta-reviews examined in this report found any evidence that receiving an influenza vaccine can cause serious adverse responses in patients

What about the non-serious responses? How much would you pay to avoid a mild fever/etc, how often does it happen?

I haven't seen all the comments on this post nor kept up with the different versions, but: have you considered doing an analysis with added information as how long into the flu season the person is? That is, the likelihood of my getting the flu this year goes down as time goes on, while the costs of getting the shot remain constant: at which point would the costs outweigh the gains?

people who may experience life-threating allergic reactions to components of the flu shot [...]

None of the meta-reviews examined in this report found any evidence that receiving an influenza vaccine can cause serious adverse responses in patients

If it's possible to have a life-threatening allergic reaction to the flu shot, and that doesn't count as "serious adverse responses", what would have counted?

A healthcare professional will be able to tell you whether or not it is safe for you to receive a flu shot prior to you receiving the immunization.

Is this actually true? And you mean this is a routine part of the procedure? How is that done?

I don't think that being a cost-benefit analysis is sufficient for something to be relevant to this site.