A vaccine-derived poliovirus (VDPV) is a strain of the weakened poliovirus that was initially included in oral polio vaccine (OPV) and that has changed over time and behaves more like the wild or naturally occurring virus.
Notably, this isn't someone reverse engineering polio from vaccines. (it's still endemic so no need)
Although arguably that's exactly what the virus did itself.
OPV is more effective at preventing Polio, the disease caused by the virus. Now, if you live in a country without endemic Polio (e.g. the United Kingdom) then that's not a big deal. You were probably never going to catch Polio anyway, and the risk (to others, not yourself) from vaccine-derived Poliovirus is a big problem, so it makes sense to prioritise that by using IPV (the vaccine based on a "killed" virus) and it is policy in countries with elimination to do so.
But, if you live in a country with endemic Polio including vaccine-derived Polio, then you perhaps want OPV because of the improved effectiveness.
Now, the other reason OPV is used in lots of poor countries with endemic Polio is that it's cheaper. It's cheaper to manufacture, and it's cheaper to administer - any idiot can give children a sugar lump with a drop of liquid and tell them to eat it and I believe it's even cheaper to store/ distribute.
We expect to figure out how to make the dead vaccine more effective than it is now, though perhaps never as effective as OPV - but it likely will not be cheaper, nor easier to use.
So they switched to IPV, which, even if it is not as effective as OPV, still offered some degree of protection, but did not cause new infections.
Sounds like an interesting tradeoff / balance act.
About a decade and half later when preparing to travel to countries where disease was more of a possibility than those I'd been to on previous trips, I mentioned to the Dr that I'd had the IPV years earlier. Hardly before I'd had time to utter another word she reached into her refrigerator took out a tiny bottle and said "here's the Sabin [OPV], stick out your tongue". A couple of drops later she said "all done."
It was all over before I'd had a chance to raise the possibility of the OPV giving one polio (which I'd vaguely heard about) and to that she said "there's a very miniscule chance - hundreds of thousands to one and even then it rarely progresses to its worst form - however in your case it's effectively zero as your earlier Salk shot would certainly protect you from what is an already weakened virus".
If one hasn't had either the IPV or OPV vaccine and there's even the slightest chance of polio being about then have the shot ASAP. If OPV is your only choice then it's far the least risky of your options. Even if you're a
vaccine denier and think COVID wasn't as bad as has been made out then think again about polio - this disease is in another league altogether.
(One day when I was in primary school a year or two before the IPV became available, a kid disappeared from my class, some months later after holidays we'd heard he'd died of polio. Another kid ended up being only able to walk on crutches and with calipers on his legs. At that time it was not unusual to see people hobbling about on crutchrd and calipers or to hear of survivors having to live permanently inside an iron lung as polio had paralyzed their respiratory muscles. Make no mistake, polio is a truly horrible disease.)
As far as I know, the OPV is safe for the person that receives it. The problem is that the virus may be transmitted to another person that may transmit it to another person ... and after a few hops mutate and give the vaccine-derived version of polio.
As my Dr said, the chances of the recipient developing polio from OPV are extremely low although she didn't state the reasons. I gather when it does happen usually there are mitigating circumstances - such as a weak immune system in combination with a vaccine whose viruses haven't been fully attenuated. Remember also that my OPV was a long while ago so these days we'd be working with updated information.
Although very rare, things can and do go wrong with vaccines - especially so during say a polio epidemic when everybody is in a panicky hurry. You've probably already read that in the 1950s during the early production of Salk's 'dead' IPV there were manufacturing problems where 'live' viruses had escaped into some finished vaccine batches and kids died as a result: https://www.washingtonpost.com/history/2020/04/14/cutter-pol....
This WP article on the polio epidemic and the botched vaccine provides an excellent summary of events and the sense of panic and fear people had (it describes events essentially as I recall them). At the time I was living in Australia but things were no different, we also had the disease and distance hadn't lessened our knowledge of kids dying from the vaccine in the US.
The article's quote that “…that polio was second only to the atomic bomb as the thing that Americans feared most,” would have equally applied in Australia. I recall the considerable anxiety and worry my parents had about the vaccine but everyone's fear of polio was much worse, so there was never any hesitation about us kids being immunized.
I'm unaware of the full extent of the political fallout from the US vaccine deaths but it's clear the tragedy delayed Australian kids from receiving the vaccine for about four to five years - for instance I didn't get immunized until I was in highschool (I think either in 1960 or '61).
This delay alone was a tragedy: for had it not happened then I'd be pretty certain that the kid in my primary school class who died of polio would not have done so. And that's just in my small world alone, similar tragic scenarios must have played out across the whole country.
It is interesting to muse about the public's overwhelmingly positive attitude to polio immunization in the '50s and '60s compared to the often hesitant and indifferent attitude of many with respect to the current COVID epidemic. Back then, despite their worries after the major tragedy of kids dying from a bad batch of vaccine, most people rationally weighed up the risk and rightly considered that being immunized with new fixed-up batches of vaccine was clearly the safest choice. It's a stark comparison with today where we have FUD and misinformation everywhere yet the newer vaccines are not only better but also much, much safer.
Undoubtedly, eventually some graduate student will do a PhD on the matter and we'll find out why a half century ago people were prepared to take sensible risks whereas today timidity and risk averseness reigns supreme.
Incidentally, another difference between the 1960s when I was vaccinated and now is that back then once the decision was eventually made to immunize kids it happened without any delay or mucking about. At my school, which was typical of other state schools, kids were vaccinated four classes at a time. Kids were lined up in the school's assembly hall in two rows of about 50 students - a line for boys and one for girls with both lines being vaccinated simultaneously - the same way recruits are vaccinated in the military. The operation commenced after the midmorning break and was complete by lunchtime - about 1,100 kids in total were processed in about two hours.
See e.g. https://en.wikipedia.org/wiki/Non-specific_effect_of_vaccine...
which links to https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2994348/
Imagine I go to a Burger King, and I declare, "Well, I shan't purchase a Big Mac. No, on principle I demand the Whopper". Sure enough the Burger King employees sell me a Whopper. But, that's not because they respect my principled stance against the Big Mac, they don't sell Big Macs and they do sell Whoppers.
Rich industrialised countries have all eliminated Polio, and thus don't offer OPV at all. I had OPV when I was a child, because I am an old man but the younger people I work with all had IPV. There was no "Which do you want?" question, government policy changed after elimination and availability of a killed vaccine.
Someone traveled from a country where the weakened live version is given to the UK. This live version mutated in that individual to become transmissible (this mutation happens in around one in a million individuals). The UK vaccinates with the non-live version. This non-live version cannot mutate, but it is non-sterilizing- the vaccinated can still become infected in their gut- the vaccine prevents it from getting into their bloodstream and become poliomyelitis. We now we see this outcome in the sewage samples.
(In fact this is the only kind of type 2 poliovirus in circulation these days - the wild version of it was eradicated a few years ago. There were a bunch of celebratory announcements of this that made it to HN which were probably rather premature. The WHO and their partners had a fancy endgame plan for this involving pulling the type 2 component of the vaccine, at which point it would go extinct for real and we'd no longer have to deal with it. This plan failed spectacularly.)
It is listed as both a pro (initially free vaccination for anyone that it gets transmitted to) and a con (once it mutates to become neurovirulent.
Now that I have some understanding of the limitations of the vaccines the idea that polio will actually be eradicated seems implausible unless we switch everyone over to the live form. I don't pretend to fully understand the subject, but the articles about cases of polio popping up seem to fit my mental model better than the one that expects to eradicate it.
UK Health Security Agency (UKHSA) experts
believe a traveller – likely from
Pakistan, Afghanistan or Nigeria - shed
the virus in their stools after being
given the oral polio inoculation.
It is likely the virus was shed by someone
who was recently vaccinated against polio
in a country where it has not yet been
eradicated, such as Pakistan, Afghanistan
National incident declared after polio detected in London sewage
Traces of polio virus found in London sewage as health officials declare national incident
Interesting there was a fake vaccination campaign conducted by our security forces in those countries.
Which has likely undermined peoples confidence in vaccines from those communities.
A doctor worked with American intelligence agencies to find the most wanted terrorist in the world. He is then imprisoned in Pakistan on made up charges, and is still in prison. Does the media sympathize with his plight. No. There is barely any coverage of this after 2012. Instead, the media is so concerned with low vaccination rates.
Is there a reason that media seems so biased to ignore a person's plight? A person who should be celebrated like a hero, not blamed like this.
In this fake vaccination program, we endangered health of some of the poorest and most vulnerable people in the world in order to catch someone who had pretty well fallen off the map and wasn't an active threat to anyone for...political points?
I have nothing to back this assertion up, but I bet the number of deaths caused by vaccine hesitancy in that part of the world due to this incident is going to dwarf the number who died in 9/11 all said and done. Was that worth it?
“To achieve herd immunity, 60% of the population must be vaccinated”
Next interview, 65%. Next interview, 70%. Then 75%
While knowing the entire time that herd immunity is impossible with a leaky vaccine.
EDIT - definitly worth a read and the aspect worth a quote "However, there still exists a version of the illness known as vaccine-derived polio, which occurs in rare incidents when the weakened virus in the vaccine mutates." Which is the instance at play here in the London sewage monitoring.
I dug in and was surprised to see that the reporting does not substantiate the narrative. Read the links in that Vox article: you'll see that the story exhibits all the hallmarks of a government-sponsored disinformation campaign. The only sources in the primary reporting (the Guardian article) are from the ISI - Pakistani intelligence. 
The New York Times' articles hint at an alternative story, which is that the ISI needed to produce something to dampen public anger over the raid that led to Osama Bin Laden's death . (That's my own crude, reductive version - it's surely more complicated than that, given the uncomfortable relationship between aid agencies and the Pakistani government):
> Dr. Afridi has told interrogators for the top Pakistani military intelligence agency, the ISI, that he was introduced to the C.I.A. through Save the Children, according to Pakistani officials and Western aid workers. Save the Children vigorously denies the claim, saying it has been made a scapegoat by a desperate man who, according to senior American officials, has been tortured in Pakistani custody.
Further along in the same article, we're given more reason not to take this story at face value:
> Dr. Afridi had a reputation for hustling as well as healing, and he faced multiple allegations of corruption and professional malpractice, according to officials, colleagues and government papers seen by The New York Times.
> At his private practice, several patients claimed he performed improper operations to make extra money, prompting a local warlord named Mangal Bagh to detain him for a week in 2008 until he paid a fine of $11,100
Again, it's certainly possible that the gist of the story is correct, but from the publicly available reporting on it, we only have the word of the CIA's counterpart.
The vaccine used in the UK is not an attenuated virus. So this was “ imported”. The news is likely being circumspect due to concerns of profiling immigrants or refugees or religious communities most prevalent where this vaccine is used.
So far no cases have been found of transmission between people.
I would be interested to know the sensitivity of the test they are using.
Many places which have the resources will then do a full sequence on any +ve samples as well to determine whether there is community transmission since this will show up as a number of related viruses which are all related to each other more closely than they are to the parent strain.
London screening frequently sees unrelated OPV strains which are due to people who have recently been vaccinated with OPV in places where that is still the preferred vaccine, what is concerning here is that the deep sequencing shows that there appears to be some person to person spread of a vaccine derived strain.
To answer your question, this is a highly sensitive and extremely specific test. Details no doubt available in the open literature somewhere.
Bet that isn't discussed anywhere.
>The location and timing of poliomyelitis cases showed spatial and temporal variability. The sensitivity of AFP surveillance to detect serotype 1 poliovirus infection in a district and its neighbours per month was on average 30.0% (95% CI 24.8–35.8) and increased with the incidence of poliomyelitis cases. The average population sensitivity of a single environmental sample was 59.4% (95% CI 55.4–63.0), with significant variation in site-specific estimates (median varied from 33.3–79.2%). The combined population sensitivity of environmental and AFP surveillance in a given month was on average 98.1% (95% CI 97.2–98.7), assuming four samples per month for each site.
>Four quarterly visits were made to 78 ES sites in 21 states of Nigeria, and ES site characteristic data were matched to 1345 samples with an average enterovirus prevalence among sites of 68% (range, 9%–100%). A larger estimated catchment population, high total dissolved solids, and higher pH were associated with enterovirus detection. A random forests model predicted “good” sites (enterovirus prevalence >70%) from measured site characteristics with out-of-sample sensitivity and specificity of 75%.
Other discussion of environmental surveillance for polio:
Whomever brought it would very possibly have done the right thing and gotten vaccinated recently, but the live attenuated polio vaccine very occasionally leads to shed attenuated polio virus reverting to full strength.
EDIT: It is possible the import could have come from an unvaccinated person too, having gotten it from someone who has been vaccinated. But that the virus is vaccine-derived means the ultimate source is someone who got the vaccine.
BTW we have a case study unfolding real time on restricting people’s travel based on vaccination status. As the COVID-19 vaccine does not prevent transmission, infection or spread, it was a complete disaster. Meanwhile unvaccinated people with natural immunity who don’t spread were unfairly punished for noncompliance.
> “Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower,” said Dr Vanessa Saliba, consultant epidemiologist at the UKHSA.
The actual numbers seem to be here:
But I am at work so can't really look. Time for me to get a booster maybe...
So the history of vacinations do become blurred. Actualy for France polio was still not eradicated as of 1988, not so in 2020 but how they count that and what the vaccine uptake was for the generations who have migrated is always going to be a factor. https://www.cdc.gov/polio/progress/index.htm
Then tourists - London does get a fair few as well, and as covid has shown, virus's dont' hang about.
GPs could do a better job of asking for your vaccine record and actually checking if its up to date though. I only found out that one of my vaccines was outdated (they need to be done again every 10 years) because I spesifically was checking my vaccines for travel.
Some US cities in the middle are like this, nobody (to a first approximation) lived there in 1901, and today there may be a small city with an airport and a decent night life. But in Europe, and on the US coasts, the cities are older.
In theory, you can separate existing combined sewers. For a town you could maybe attempt this as a large local infrastructure project over the course of a year or two, in a small city this is a large and expensive project that could take decades to complete. For somewhere like London or San Francisco it's unthinkably costly and won't be attempted in the foreseeable future.
A small sign of willingness to attempt this, combined with the difficult reality of such work goes like this, I live in Southampton, an important port city on England's south coast:
1. Legally, if you fit a new grey water waste (e.g. from a shower, or a washing machine), it should flow into the sanitary sewer, which your home is plumbed into usually via large black pipes that run mostly vertically up the side of the building. It must not flow into the storm water sewer, which is often smaller rectangular pipes connecting to the gutter where they collect roof water.
2. But, there's probably a gutter pipe right near where your waste is, while the sanitary sewer could be on the far side of the property. So, does the plumber do the extra work, and charge you for it? Or do they just cut into the storm water sewer and save their time and your money?
3. Result: Now if you separate the storm water sewer, it has grey water waste flowing into it, and you're dumping that into the sea. Oops.
The big problem in San Francisco is that during severe rainstorms the flow rate overwhelms the treatment plant so they have to dump the overflow. but at that point it is mostly rainwater so it's not quite as bad as it sounds.
For example, how many cubic metres of rain water makes adding one human turd OK ? A million seems fine, doesn't it? Like, who cares about just one turd in so much rainwater. How about a thousand, that's a swimming pool (not Olympic, but decent sized) with a turd in it, is that OK? Start to feel a bit uncomfortable with how much shit there is in the water? What if it's a hundred? Are you sure San Francisco, or London, can promise you their CSOs have at least that ratio?
(Disclaimer: I vaguely worked on software projects that were CSO mitigation adjacent. Which at least explains some the interest in the projects.)
Then in the event of heavy rainfall there is much less poop in the overwhelmed (mostly) rainwater treatment plant.
# Solid human waste will clog the smaller pipework and now your toilet waste is overflowing inside the home and the occupants are very angry
# The fittings don't "fit". The local plumbing supply store has the adaptor you need to run grey waste into rain water drains, even if it says that's not what it's for, but it does not have adaptors to run a large diameter soil pipe into the storm drain, that's a recipe for disaster they want no part in and the part has no other purpose.
If you indicate that you've got some "good" reason to attempt this, they'll sell you an expensive macerator which solves the first problem by grinding up waste, and as a result the output is smaller diameter waste pipes - but now your project is more expensive and more complicated to install.
One segment at a time, I guess. But like you said, it gets really complicated in older cities with many hundreds of years of things having been put in the ground. Anyway they can probably process that just fine, it just means that at rainy days there will be higher water content; it means they'll have to scale up. Or if there's overflow, dump it directly if they're already doing it now; if they can reduce the amount of sewage going into surface water, it's already an improvement.
Can anyone explain why it's rare for inactivated vaccines to be able to be delivered via the oral route? It would have been a lot more efficient/user-friendly to deliver the Coronavirus vaccinations in this manner, but almost all of the vaccines we seem to use nowadays appear to be intramuscular injections.
* designing a formulation that can survive the harsh gastrointestinal environment. For example, COVID-19 vaccines, especially the mRNA-based ones, are especially fragile and degrade rapidly at room temperature even under normal conditions.
* Avoiding mucosal tolerance. Many antigens that would evoke an immediate immune response if encountered in the blood stream are ignored by mucus tissue, to avoid your body creating hundreds or thousands of spurious immune responses every day to antigens occurring in your food. For an oral vaccine to be effective it must get around this tolerance to provoke an effective immune response.
For respiratory viruses, another promising delivery method would be intranasal, and indeed there are some COVID-19 vaccines in development that use this route. The bottom line is, developing vaccines is already complicated and costly, so unless there is a guaranteed large market demand pharmaceutical companies are unlikely to invest in delivery methods that add additional research challenges.
whether it is worth the trouble also depends on the method of infection. The live attenuated oral polio vaccine creates gut immunity, which is helpful because polio is passed via ingestion of infected materials. Gut immunity is less useful if a disease is passed via inhalation.
Live attenuated viruses create viral shedding, which creates a chance of passing the virus and are administered using oral drops.
Inactivated virus vaccines, do not create viral shedding, cannot pass off the virus, and are administered using an injection.
In general, attenuated viruses have the potential to create viral shedding and by extension pass on an infection. The fact that the live attenuated polio vaccine is done via drops is a secondary design decision for , gut immunity, shelf stability, ease of administration, etc. That it is oral drops itself does not cause the chance of passing on the virus.
Ars technica had a fairly thorough article about all this:
The linked PDF contains the names of that product in different European countries on the last page.
There is now debate on whether there is a need to 'freshen' up (boost) tetanus protection, due to a study published in 2020 that showed tetanus boosters give no benefit [1,2,3].
(The 2nd and 3rd references are discussing the study in the 1st reference)
They even use the same vaccines.
If you are younger than 30 you will have had a polio vaccine if you parents followed the national vaccine programme in any European country. If you are younger than 50 chances are that you have been vaccinated as well.
The advantages of this are that it's very easy to administer (this is the classic "vaccine dropper onto a kid's tongue" image), and because you shed the attenuated virus, you can help boost the immunity of those who aren't directly vaccinated.
The downside is for the polio vaccine that it occasionally reverts back to a type that causes active disease. This is rare, but definitely happens, and this is one of those cases.
Very occasionally the attenuated virus version can cause onward polio infections, i.e. the vaccinated individual can pass the virus on to others.
There was however a lot of skepticism and debate about the Covid vaccine because risk/reward is much more ambiguous.
That's just one of a myriad of conditions that cause paralysis.
What are "anti vax statistics"? Do you think people who refused to take the COVID vaccines were making up their own data from whole cloth? I never saw that. What we do see is that the stats presented by health authorities are often mangled by inappropriate methodologies that appear to be picked in order to arrive at pre-chosen outcomes. When the raw data is obtained and re-analyzed correctly, we get papers like this one:
"The excess risk of serious adverse events of special interest surpassed the risk reduction for COVID-19 hospitalization relative to the placebo group in both Pfizer and Moderna trials (2.3 and 6.4 per 10,000 participants, respectively)."
In case you're the sort of person who evaluates arguments based on credentials not merit, the authors of this paper are all from universities or health services. One is an editor of the BMJ. One is a professional statistician and epidemiologist (https://en.wikipedia.org/wiki/Sander_Greenland)
You assert that the modern COVID anti-vax movement is "conspiracy driven". But there are two problems with this argument:
1. It's not really true. Refusal arises because public health officials have repeatedly lied about the vaccines, saying things like they are 95% effective against infection, or that they'll turn people into "dead ends" for the virus. That second one was the rationale for mandates and it was known to be false from the start - the trials never showed any such thing and they had no reason to believe this given that non-sterilizing vaccines are common. As for the first, the governments that publish actual case rates by vaccine status show that they have effectiveness in the minus 300-400% range i.e. vaccinated people get COVID at a much higher rate than unvaccinated people. So that wasn't true either.
2. Even if it was the case that it was all driven by conspiracy thinking, so what? It's already been proven beyond all reasonable doubt that public health leaders engaged in multiple conspiracies throughout COVID, e.g. virologists writing in private emails that they thought the virus looked like it'd been modified in a lab, and then days later signing an open letter saying the opposite. Or public health flipping from "masks are useless" to "masks are essential" overnight without any new science to drive it.
Given this history the argument that anyone proposing the existence of a conspiracy is illegitimate is, well, extremely naive.
"The risk of course is when the vaccines are defective such as with The Cutter Incident in the 1955. This was probably the root of the modern anti-vax movement"
The anti-vax movement existed from the very start. Research the history of the smallpox vaccine. Parents were choosing to go to prison for violating mandate laws rather than let their children be vaccinated because they'd seen that vaccinated children came down with actual smallpox at much higher rates than expected. Just like today, public health refused to countenance the possibility that there were any possible problems in the vaccination process. They never change. It's a psychological issue.
Some guy in a lab coat wrote down he did a clinical trial somewhere in the 3rd world, and the government just takes his word for it. Then when you have a whistle blower like on the Pfizer trials, who claims patients were unblinded and side effects weren't accurately recorded, people just slap the old 'conspiracy' label on it.
Before 2021, most people didn't even know VAERS and the National Vaccine Injury Compensation Program even existed. Now the CDC is telling us the reporting system they manage is inaccurate. Okay, so what have they been doing for the last 40 years?
They finally admitted that the vaccines are affecting some women's cycles, but downplayed it by saying 'on average it's about 1 day shorter between cycles.' That doesn't sound like much, but many women have a very short window of time from conception to implantation before their period starts, and that would be more than enough time to render those women unable to carry a baby.
People discovering things because they start paying attention doesn't make them new.
Do you think VAERS functions adequately in this capacity? Which vaccines have had safety signals that lead to rescinding the license, or otherwise limiting use? Or is the FDA batting 1000?
VAERS is also important for monitoring the rotavirus vaccines - it was one of the data sources that pulled the RotaShield vaccine off the market due to increased risk of intussusception in 1999.
"Since CDC officials stated publicly that “COVID-19 vaccine safety monitoring is the most robust in U.S. history,” I had assumed that at the very least, CDC officials were monitoring VAERS using the methods they described in a briefing document posted on the CDC website in January 2021 (and updated in February 2022, with minor changes) [PRRs]. I was wrong."
This had to be forced out of them with a FOIA request but their response to the request (for documents related to VAERS analysis of COVID vaccines) says:
"no PRRs were conducted by the CDC. Furthermore data mining is outside the the agencies purview, staff suggest you enquire with the FDA"
The CDC run VAERS but have never actually done any data mining on it, despite telling the public that the monitoring of COVID vaccines was the most robust in history. Which means that statement they gave is either a lie, or it's true and VAERS has actually never been used to detect safety signals.
There was a FOIA request a few years ago (can't remember the name of the organization, search engines have buried these type of results) that the agency in charge of post-license safety review of vaccines has never conducted a single review since the law passed in the 80s or early 90s.
"You assert that the modern COVID anti-vax movement is "conspiracy driven"
You pretty much just made up everything you say I said. I get it you had something you wanted to get off your chest so you dropped it on me. No worries.
Still, there's a secondary question here: how do we know polio vaccines are genuinely so different? COVID vaccines are one of the first mandatory vaccines to be developed and forced on people in the internet era. Thanks to that and the lawsuit that's forcing documents out of the FDA, the world has far more insight into the development and marketing of these vaccines than any previous public health campaign in history. What we see from this evidence is disturbing, and it seems to be a pattern, which raises the question of whether this is really the first time public health people have been misleading people about vaccine effectiveness and safety.
If it's not, then it becomes hard to say much with any certainty on the topic, as those sources control all the data.
Many other types of vaccine exist, and modern vaccines tend to be neither inactivated nor attenuated virus.
The tricky thing about finding it in London is that since they found it in sewage sampling, they don't yet know if it originated from the UK's vaccine program or an international source. They'll have to do more digging to narrow it down.
EDIT: as per peer comment from the UKHSA, it's believed to be from an international traveler or resident from a country where polio is still endemic and not yet eradicated. This is a good reminder to keep up on one's vaccinations, as herd immunity statistics are impacted by ubiquitous international travel.
If the virus is vaccine derived, shouldn't they search for the vaccine which is causing it ?
>It is not known how long people who received IPV will be immune to poliovirus, but they are most likely protected for many years after a complete series of IPV.