Is Herd Immunity Just...Luck?

I’d be interested to hear others’ thoughts on this - if herd immunity is just playing the odds? I never had chickenpox as a child. At age 28, in the 1990s (pre-chickenpox vaccine era), I broke out with chickenpox. A day or so prior, a lady was sneezing at the office. She sat two cubicles over from me. We both sat in the back row where the cubicles are more open. I thought nothing of it at the time, but once I recovered and returned to the office, she volunteered her child broke out with chickenpox the same time I did. It’s clear to me she acted as a carrier. Is it fair to say I had what equates to herd immunity until my luck ran out?
(Also, consider Americans who in recent years developed smallpox when we thought it was eradicated, and I understand we stopped immunizing against it for quite some time. Another case of herd immunity’s Achilles Heel?)

Herd immunity is based on the notion that if most of the people in a population already have immunity (acquired either through infection or immunization), then the virus can’t spread readily because it can’t find a susceptible host. You may have benefited from herd immunity up until age 28, in that most of the people around you had had chicken pox and were no longer spreaders, but you didn’t have it yourself.

(The last cases of smallpox were in the 1970s; none have been seen in the wild since 1975 in Bangladesh [variola major] and 1977 in Somalia [variola minor]. You may be thinking of measles or whooping cough, which are still recommended vaccinations in the US but which have seen an uptick mostly due to anti-vaxxers.)

No it’s not luck (no more than any disease, or to put it another way all disease is ‘luck’ and this is no different), it’s that the disease can’t spread faster more than it dies out - which is a simple mathematical evaluation. Since it can still can spread ‘luck’ is not a factor, just your chances of contracting it are reduced but not zero.

So it’s not luck, merely chance?

Pretty much the same as not having piles of oily rags laying around your house doesn’t guarantee that you won’t have a housefire.

Said another way, “herd immunity” is a property of a herd, not an individual. In general, the herd as a whole is less susceptible to the disease than any single individual within it is susceptible to the same disease.

What protects the herd as a whole is that spread opportunity is greatly reduced by the presence, by whatever cause, of lots of immune individuals. There will still be outbreaks, but they won’t spread far and wide.

A fire in a modern city doesn’t spread quickly and tends to die out. A fire in 1880s Chicago spreads quickly and expands rapidly, consuming nearly everything in its path. The difference is how many areas of non-fire-susceptible stuff or barely fire-susceptible stuff there is to throttle down the rate of spread.

Say wha…?

Thank you. I had to check to make sure I wasn’t misremembering, and that smallpox is, indeed, gone for good.

ISTM that herd immunity may not be very workable for this disease, because there are some indications that the virus happily infects a variety of animals too – pets, farm livestock, and wild animals. If it continues to spread through those, then herd immunity among the humans might not help much.

Keep your pet pangolins quarantined!

I’m not sure how much the ability to spread to pets is a problem. Everything I’ve seen shows the numbers for them getting infected is quite small compared to humans infected, and the likelihood of spread from them seems even smaller.

Unless it’s rather large, the most it could do to herd immunity is require that more people need to be inoculated to reach it. And, if it’s widespread enough, there will likely be inoculations for the species that humans tend to encounter, whether pets, livestock, zoo animals, and so on.

I’m personally more concerned about mutations and even partial vaccine escape than I am about animal reservoirs at this point, based on what I know. But, of course, I’m not any sort of expert.

Agree with this.

IMO even more worrisome is the perpetual human reservoirs of the anti-vaccine crowd and the [unvaccinated because they live in a shithole country] crowd.

The former is and will remain the closest snake in the USA and perhaps the UK+EU and similarly situated countries.

On a planet-wide basis, the latter is the central issue. We just can’t have 16th Century poverty and public health capabilities connected by 21st Century transportation to the 21st Century world without Mother Nature’s diseases dragging everyone back to the 16th Century of endemic eternal disease and pestilence.

Part of the problem is that the two overlap a bit, and I can’t blame them.

We laugh at those who claim some sort of conspiracy about vaccines, but in some areas of the world, vaccine drives were actually used by the CIA to gather intelligence or apprehend people. Some of those vaccine drives were legitimate and simply had intelligence operatives embedded, but some were entirely illegitimate, and served only as fronts.

Hard to get people to come out when we’ve already abused their trust.

Sorry, I am just getting a chance to reply and clarify a point on which I guess I heard wrong. About smallpox: I guess I heard something wrong or something was misdiagnosed or misreported somewhere down the line. I thought I had heard (at some point in time) of small resurgence of smallpox at a college in New England, or such. Google turned up nothing. So, I have apologize for the misinformation and retract that statement.