Cost-benefit analysis of my vaccination against the flu

Vasco Grilo🔸

Summary

I estimate the benefits of my vaccination against the flu would be 44.9 % of its cost. I calculate I would have to receive more than 24.7 $ for it to be worth it, which is the difference between my estimates for the total cost and benefits of 44.8 and 20.1 $.
I have not considered the effects of my vaccination on other people, soil animals, or microorganisms, but they do not change my decision. I think they are much smaller than the effects on my work and donations resulting from the time and monetary costs of my vaccination.

Benefits

I assume 0.0610 symptomatic flus per person-year. This is the estimate for unvaccinated people with symptomatic influenza, age from 18 to 64, and a season of moderate severity in the United States (US) from the meta-analysis of Tokars et al. (2018), which is in Table 2.

I suppose the symptoms last for 5.50 days, which is the mean between the lower and upper bound for the duration of the symptoms from Nichol (2021). “The typical case of influenza may be characterized by the abrupt onset of fever, sore throat, nonproductive cough, myalgias, headache, and malaise. Symptoms usually last 5 to 6 days”.

From the 2 estimates above, I infer 0.336 days with a symptomatic flu per person-year. Multiplying this by 9.33 h per day I have logged in my time sheet from 10 May 2021 to 19 September 2025, and a decrease in productivity of 2/3 due to symptomatic flu, I conclude I am willing to log 2.09 h less in my time sheet for not having flu over 1 year.

I determine the benefits of a single vaccination against the flu are 64.3 % of those of not having flu. This is based on the vaccine against the flu being a good match with probability 78.5 %, and having benefits equal to 75.0 % of those of not having flu in this case, and 25.0 % if it is a poor match. These estimates are the means between the lower and upper bounds in Table 6 of Nichol (2021). 72 % to 85 % probability of the vaccine being a good match, 60 % to 90 % vaccine efficacy in this case, and 0 to 50 % if it is a poor match.

From the 2 estimates above, I am willing to pay 1.34 h more in my time sheet for a single vaccination against the flu. I assume 1 h more is worth 15 $ for me. So I think a single vaccination against the flu is worth 20.1 $ for me.

Cost

I estimate a single vaccination against the flu would have a monetary cost of 19.0 €. This is the mean cost of the 3 vaccines against the flu available in Portugal in 2025 for people not covered by the free vaccination program according to Deco Proteste, Influvac (8.83 €), Vaxigrip (13.15 €), and Fluenz (35.16 €). For 1.17 $/€ on 20 September 2025, I obtained a monetary cost of 22.3 $.

I guess I would have to spend 1.5 h to be vaccinated against the flu. In addition, I am willing to log 1 h less in my time sheet to save 1 h on the vaccination against the flu. So I am willing to log 1.5 h less to save the time I would spend on the vaccination against the flu. Since 1 h more is worth 15 $ for me, I conclude the time cost of a single vaccination against the flu is 22.5 $.

Adding the 2 costs above, I get a total cost of a single vaccination against the flu of 44.8 $, of which 49.8 % is monetary cost, and 50.2 % is time cost.

Benefit-to-cost ratio and break-even monetary benefit

I estimate the benefits of my vaccination against the flu would be 44.9 % of its cost. I calculate I would have to receive more than 24.7 $ for it to be worth it, which is the difference between my estimates for the total cost and benefits of 44.8 and 20.1 $.

I have neglected the cost from serious illness, which I expect to be minor for me. However, I believe accounting for it may well make vaccination worth it for people who are, for example, 65 or older.

I have not considered the effects of my vaccination on other people, soil animals, or microorganisms, but they do not change my decision. I think they are much smaller than the effects on my work and donations resulting from the time and monetary costs of my vaccination.

Acknowledgements

Thanks to Joanna Michalska for a message which prompted me to do this analysis. The views expressed in the post are my own.

15 Reactions

More posts like this

Comments3

Sorted by

New & upvoted

Click to highlight new comments since: Today at 9:00 PM

NickLaingDec 157

You might me missing the positivity herd immunity effect on others, which is a factor even with the low 40%ish of the population that is immunised. But yes its debatable whether its worth it for someone your age to get the flu vaccines, which is why most governments don't fund it for young people.

https://www.thelancet.com/journals/lanpub/article/PIIS2468-2667(17)30004-X/fulltext

Vasco Grilo🔸Dec 152

Hi Nick. Fair point. I thought about those effects, but should have explained why I did not cover them in the post. I have now added the following to the summary and main text.

I have not considered the effects of my vaccination on other people, soil animals, or microorganisms, but they do not change my decision. I think they are much smaller than the effects on my work and donations resulting from the time and monetary costs of my vaccination.

My marginal earnings go towards donations, and I believe donating the difference between my estimates for the cost and benefits of 24.7 $ to the most cost-effective global health interventions would increase human welfare more than the benefits of my vaccination to other people. GiveWell published a report on dietary salt modification in July 2025 where they concluded the following.

Overall, we estimate that it costs about $855 to avert a death via dietary salt modification in China and India, and the intervention is about 14 times as cost-effective as spending on unconditional cash transfers. However, this is a preliminary estimate that we plan to refine with additional work.

According to Coefficient Giving (CG), “GiveWell uses moral weights for child deaths that would be consistent with assuming 51 years of foregone life in the DALY framework (though that is not how they reach the conclusion)”. Assuming 51 DALY/life, the above cost-effectiveness would be 0.0596 DALY/$ (= 51/855). So 24.7 $ would avert 1.47 DALYs (= 24.7*0.0596). Supposing 1 DALY/symptomatic-flu-year, which greatly overestimate the badness of having a symptomatic flu, my vaccination would only be worth it if it averted more than 1.47 symptomatic-flu-years (= 1.47/1) in other people, or 97.6 symptomatic flus (= 1.47/(5.50/365.25)) for my assumption of 5.50 days of symptoms per symptomatic flu.

The benefits to other people would only materialise in cases where the vaccination prevented me from getting a symptomatic flu, which is when I could have infected other people. Combining the above with my assumption of "0.0610 symptomatic flus per person-year", I estimate I would have to have infected 1.60 k (= 97.6/0.0610) people conditional on getting a symptomatic flu for my vaccination to be worth it. In contrast, I would only contact with a few people if I had a symptomatic flu.

I believe I should consider effects not only on other people, but also on all potential beings. I suspect effects on soil animals and microorganisms are the driver of the overall effect, and I have very little idea whether their welfare would be increased or decreased. In any case, I think the conclusion accounting for all beings would still be that I should optimise for increasing the impact from my work and donations, which points towards my vaccination not being worth it.

JasonDec 152

This is one of those scenarios in which I think it's easier to capture ~the full costs than the full benefits:

Would you assign value to the indirect protective effect on those you live with (if any), friends, and family members? Apparently the flu household attack rate can be all over the place depending on strain and other factors, but 15-20% may be reasonable guesses in general (source: AI overview on Google search, very low confidence).
This gets into some tricky situations with housemates; you're likely to all be better off if you mutually agree to consider the indirect protective effects on housemates when making your own decisions. But that effect is likely to be significantly greater with unvaccinated housemates than vaccinated ones. If you live with three other people, the first vaccination may have significant household spillover effects; the fourth not so much.
Most people would pay to avoid the discomfort of having the flu (above and beyond the loss in productivity) or would demand payment to willingly undergo that discomfort. Maybe you could consider willingness to pay for pleasurable leisure activities, and then decide how many of those activities you'd be willing to forego to avoid enduring one average case of the flu?

On the costs side:

1.5 hr is a lot to get a flu vaccine by US standards; they are available on a walk-in basis at pharmacies everywhere. That's not a critique of your analysis, of course.
Could you call ahead and ensure that where you were going to get the vaccine used Influvac or Vaxigrip? (I assume fewer places would stock Fluenz, anyway due to cost.)
For most people, the hours of their day do not have equal value or utility. I can't -- at least not on a regular basis -- realistically use the 14th most valuable hour of my day for renumerative work, but I could use it to get a vaccine. In other words, there's a limit on how many hours I can sustain higher-demand activities. In contrast, when I get the flu, I think the loss in productivity hits the relevant time slots more evenly.

I don't know if those adjustments would flip the end result for you -- but I think accounting for them would make it a close call and would show how modest differences in the factors (e.g., personal circumstances that make getting the vaccine less time-consuming) would flip the outcome.