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Comment by ifyoubuildit | Hacker News Reader

Are you sure? Your link ends with this:

> Combined with the brutal arithmetic at higher R0R_0 R0 , this is a large part of why flu vaccination programs are generally justified on individual protection against illness and severe outcomes rather than on a realistic expectation of achieving herd immunity and stopping circulation.

On the one hand, in a military setting you can feasibly achieve 100% compliance. But if you don't stop transmission (which it sounds like we don't have good data saying it would), you don't get herd immunity.

So I think you're back to just the benefits of reduction in disease, which is not nothing, but it is marginal like I said originally.

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I mean, I would say that preventing 40% of disease (depending on what you're measuring, etc etc) is not marginal. I guess I'd turn it around and ask, if 40% is marginal, what number would not be marginal, and why do you draw the line there?

(For me, "marginal" would mean that the costs were roughly equal to the benefits. I think you'd have a hard time convincing me that saving the lives of even just 1% of the people who would normally die from the flu -- between 10k and 50k people a year -- is roughly equivalent to the cost of giving out flu shots. I suppose you could argue that the benefit is marginal to individuals who have a low probability of dying from the flu, and marginal to a society which has relatively low vaccination rates overall.)

The other thing is that, according to the Claude data here, the vaccine is actually relatively effective at preventing the transmission of some flu variants, 50% effective against influenza B! If so, there would be a clear group benefit to that, you only need (1 - 1/1.3) / 0.5 = 46% of people to be vaccinated to achieve herd immunity to that strain.

The relevant question for me would be how many people would be combat ineffective for how long with and without the flu vaccine. Your Claude conversation says things like this:

"The best recent direct measurement is the FLUTES study (JAMA Network Open, 2024), which tracked secondary infections after flu entered US households across 2017–2020. The result: the estimated effectiveness of influenza vaccines for preventing secondary infections among household contacts was 21.0% (95% CI, 1.4% to 36.7%). Note how wide that confidence interval is — the lower bound is nearly zero."

And

"This is consistent with older household work. A 2013 study found no evidence that vaccination prevented household transmission once influenza was introduced; adults were at particular risk despite vaccination — strikingly, 9 of 11 adults with household-acquired influenza were vaccinated in that sample."

So most people on base who were going to get infected and transmit are still going to do so. Some portion of them have a better time with the illness if it does come around, which won't happen all the time. Contrast that with the costs of the program (side effects, time, whatever cons you can think of), and it seems like you might not be in slam dunk territory.

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