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.

Thanks for the good points, Jason.

Would you assign value to the indirect protective effect on those you live with (if any), friends, and family members?

Yes. However, I estimate I would have to infect more than 1.60 k people conditional on getting a symptomatic flu for the health benefits to other people to exceed the impact of donating 24.7 $ to the most cost-effective global health interventions, which is the difference between my estimates for the cost and benefits. I would also limit my contact to a few people I live with if I had a symptomatic flu.

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?

I think my willingness to pay for extra working and leisure time should be the same. Otherwise, I should spend more/less time on what I think is the most/least valuable per hour at the margin until my willingness to pay for extra working and leisure time is the same.

• 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.)

Interesting. In Portugal, people like me who are not covered by free vaccination need to get a doctor's prescription.

For people not covered by free vaccination, the flu vaccine is dispensed at community pharmacies with a doctor's prescription and subject to stock availability.

I also assume I would have to book it in advance to ensure there is enough stock, and because people who are covered by free vacination also have to book it. My time cost of 1.5 h is supposed to account not only for the time to get the vaccine, but also booking it, getting a doctor's prescription, and understanding whether this is even feasible in the 1st place (considering I am a healthy young adult).

• 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.

Nice point. I should clarify I am considering as productive all the activities I log in my time sheet, not just my main activity of paid work. Ideally, the marginal hour spent on each activity would be the same. In any case, I agree there are times in the day that are less productive. I would prefer to get a vaccine late in the afternoon just before dinner than in the middle of the morning or afternoon.

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.

Yes, I can see vaccination being worth it for young healthy under some conditions. Thanks for bringing attention to this.

Hi Wayne. You are right I did not account for the possibility of serious illness.

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.

Here is an estimation of the harm from serious illness which is in agreement with my statement above. The disease burden, which accounts for mortality and morbidity, from lower and upper respiratory infections among people with age 25 to 29 (which covers my age) in Portugal (where I live) in 2023 was 0.00113 DALY/person-year (= (4.98 + 6.29)*10^-4). This corresponds to a loss of 0.413 d/person-year (= 0.00113*365.25), and therefore 3.85 h/year (= 0.413*9.33) less logged in my time sheet assuming all the disease burden from lower and uper respiratory infections is linked to the flu (which overestimates the damage caused by this). I got 2.09 h/year less neglecting serious illness, which suggests this accounts for a loss of 1.76 h/year (= 3.85 - 2.09). However, for the 2024-25 flu season in the US, only "11% of all patients hospitalized with influenza did not have any underlying medical conditions", which applies to me. So I guess my expected harm due to serious illness caused by flus is 11 % as large, and implies logging 0.194 h/year (= 1.76*0.11) less in my time sheet. As a result, I estimate the harm from serious illness is 9.28 % (= 0.194/2.09) of my original estimate neglecting serious illness.