First off, it's not really an outbreak, it's one case of polio in Rockland County, NY, but such is the power of collective memory that even just that one case has engendered something of a panic in the rest of the country and beyond, particularly in the wake of the COVID-19 and monkeypox outbreaks.
Polio was the scourge of patents and toddlers worldwide from its first identification in the 1890s until its eradication in 1979 in the USA, and its almost-eradication in the rest of the world. Currently, just a handful of cases occur each year in countries like Nigeria and Yemen, which is why the US case has come as such a shock.
It's no surprise that it occurred in Rockland County, though. Rockland has the lowest vaccination rates in the state, and as a result has suffered some crippling COVID-19 numbers and a recent measles outbreak. Its polio vaccination rate stands at around 60%, compared to 90% or above in the rest of the country. (Herd immunity for polio is estimated at around 80%.) And the 20-year old youth infected this week, was indeed unvaccinated.
Nobody is talking about it - presumably because it is considered not politically correct - but a good part of the reason Rockland County is so under-vaccinated is due to the large population of ultra-traditional Orthodox Jews, many of whom believe that vaccination is against Jewish law in some way. (By the way, it's not, according to Jews who are also medical doctors, and even most eminent halachic scholars - in fact, Jewish law positively encourages it, if it will help to protect the body, but you try and tell that to some of the more fundamentalist rabbis.)
What is perhaps more interesting, though, is that the case is described as "vaccine-induced". While some people with an axe to grind will almost certainly blame it on COVID-19 vaccines, it is nothing to do with that. Back in 1955, Dr. Jonas Salk famously developed his highly-effective injectable inactivated vaccine. But, in 1961, Dr. Albert Sabin came up with an oral live-attenuated vaccine, which also granted 99% immunity, and it was this (cheaper and easier to administer) vaccine that became the most widely used, at least until polio was effectively eradicated in 1979. After the 1980s, the slightly less risky injected vaccine became the norm, as it still is today.
Many other (poorer) countries, though, still use the oral live-attenuated vaccine, which uses a modified weakened strain of the disease, rather than the inactivated dead viral material that the injected vaccine uses. This doesn't actually cause illness in humans, but is enough to trigger an immune response (except in severely immuno-compromised individuals). The problem is that, if a live-attenuated vaccine is used in a community with a high proportion of unvaccinated people, there is a small risk that, with enough generations of spread, it can mutate back into a new virulent strain. This seems to have been what happened in the current US case.
So, what can be done? Well, we can encourage (and subsidize?) those countries still using the riskier oral polio vaccine to switch to the safer injected version. And those hold-outs in Rockland County and elsewhere just need to suck it up and get their shots, for their own good as well as everyone else's.
That said, the 20-year old in Rockland is now considered no longer contagious, and a full-blown outbreak is extremely unlikely (although it has been genetically linked to spread in England and Israel, so the risk is not over). This time, at any rate.
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