It’s true, polio has been eliminated in the United States.
But that doesn’t mean that we can stop vaccinating kids against polio yet.
Why Do We Still Vaccinate If Polio Has Been Eliminated?
For one thing, the last polio case in the United States was a lot more recent than 40 years ago.
What happened 40 years ago?
That was when we had the last endemic case of polio in the United States, in 1979. After that, in addition to cases of VAPP, there were at least 6 cases of imported paralytic poliomyelitis. In fact, the last case of wild polio in the United States was in 1993, just 26 years ago.
And just ten years ago, in 2009, was the very last case of VAPP, a patient with a long-standing combined immunodeficiency who was probably infected in the late 1990s, even though she didn’t develop paralysis until years later.
But still, why couldn’t we stop vaccinating against polio in the United States, even though polio isn’t eradicated yet? After all, we stopped using the smallpox vaccine in 1972, before smallpox was declared eradicated (1980).
While that is true, smallpox isn’t as contagious as polio and there hadn’t been a case of smallpox in the United States for over 30 years when we stopped using the vaccine.
Until wild polio is eradicated and the oral polio vaccine isn’t used anymore (OPV switch), we must continue to vaccinate against polio to prevent new outbreaks.
That is the polio eradication and endgame strategic plan.
Over the next few years, the world will hopefully switch to using just the injectable form of the polio vaccines, which eliminates the risk of VAPP.
But if we are so close, why not just stop vaccinating in those parts of the world that don’t have polio?
Because we are so close to eradicating polio.
Why take the risk of polio spreading from one of the remaining endemic countries, paralyzing kids, and putting eradication efforts further behind?
Unless you have a true contraindication to getting vaccinated, until a disease is eradicated, the benefits of a vaccine will typically be far greater than its risks.
The switch from the live, oral polio vaccine to the inactivated vaccine is a good example of when this wasn’t the case though. Since OPV could rarely cause vaccine-associated paralytic polio (VAPP), once polio was well controlled in the United States, the risk of this side effect became greater than the benefit of continuing to use the vaccine, but only because we had an alternative polio vaccine that didn’t cause VAPP.
Similarly, the original rotavirus vaccine was withdrawn because the extra risk of intussusception, even though it was small, was thought to be greater than the benefits of the vaccine.
In the great majority of cases though, to think that getting vaccinated is a bigger risk than getting a vaccine preventable disease, you have to buy into the anti-vaccine hype:
There is a lot more interest in polio these days, but not because we are close to eradicating this deadly disease, but rather because of the emergence of cases of acute flaccid myelitis (AFM).
Although the cases have a different cause, the symptoms of AFM are the same that we used to see during the outbreaks of polio that used to hit each summer in the pre-vaccine era.
Surprisingly, in most people, the poliovirus doesn’t actually cause any symptoms. They simply have an asymptomatic infection.
In some others, the poliovirus causes flu-like symptoms, including a fever, sore throat, nausea, and a headache – symptoms that last about 3 to 5 days.
Much more rarely, the poliovirus causes meningitis or paralysis.
It is these cases of paralytic polio that most people are aware of and that panicked parents during summers in the 1940s and 50s.
After having flu-like symptoms, those kids who would develop paralytic polio can develop pain and then flaccid paralysis.
“The most severe form, paralytic poliomyelitis, which is seen in less than 1% of patients, presents as excruciating episodes of pain in back and lower limbs. In children, the disease may present in biphasic form—a period of prodrome followed by a brief symptom-free period of 7 to 10 days and then appearance of asymmetrical paralysis of limbs. Flaccid paralysis is the hallmark with loss of deep tendon reflexes eventually.”
Mehndirattta et al on Poliomyelitis Historical Facts, Epidemiology, and Current Challenges in Eradication
Of course, polio wasn’t always called polio.
Other names have included infantile spinal paralysis, infantile paralysis, Heine-Medin disease, poliomyelitis anterior acuta, and acute anterior poliomyelitis.
The first use of the name “polio” came from Adolph Kussmaul, with his use of the term poliomyelitis anterior acuta, which was derived from the Greek polios “grey” and myelos “marrow” and itis “inflammation.” It was because he knew that it was caused by inflammation of the spinal cord gray matter, even if he didn’t know why.
Polio didn’t just suddenly appear in the middle of the 20th century though, it was likely around for ages.
In addition to an Egyptian funeral stele (a stone slab used as a monument) portraying Roma the Doorkeeper from 1500 BCE that suggests he had paralytic polio, archeologists have found evidence of polio in skeletons as far back as the Neolithic period.
Still, we don’t really know how long polio has been around and we don’t know why we began to see more cases in the mid-20th Century, although there are theories, including, ironically, about hygiene. While we often credit improved sanitation and hygiene for helping to reduce mortality from many diseases, some think that this actually set us up for polio outbreaks, as we were no longer exposed as infants, when we still had some maternal immunity.
The one thing that we do know is that we are on the verge of eradicating polio, as there are very cases now, in just a few countries.
Polio Timeline and Milestones
In addition to the more ancient discoveries about polio, there is a lot to learn about vaccines and vaccine-preventable diseases if we look at the major milestones of this important disease.
Although in the end it is a success story, the road to figuring out what caused polio symptoms and how polio could be prevented was very long.
Michael Underwood describes what is thought to be paralytic polio in his book A Treatise on the Diseases of Children, with General Directions for the Management of Infants from Birth in a section on “Debility of the Lower Extremities” (1789)
first reported outbreak of polio in Worksop, England (1835)
Jacob von Heine, head of an orthopedic hospital in Germany, publishes a monograph that describes 29 cases of paralytic polio, and actually attributes the condition to inflammation of the anterior horns of the spinal cord, although the cause was still not known (1840)
first use of the term poliomyelitis by Adolph Kussmaul (1874)
Nils August Bergenholtz reports on an outbreak of paralytic polio in Sweden (1881)
Karl-Oskar Medin, a pediatrician who reported on a polio epidemic in Sweden (1887), later presents his findings at the Tenth International Conference in Berlin (1890)
the first major outbreak in the United States is documented in Rutland County, Vermont and causes 132 cases of paralysis and 18 deaths (1894)
Ivar Wickman tracks cases of polio during an epidemic in Sweden in 1905 and was the first to suggest that polio was contagious and that you could get it from “those afflicted with the abortive type” (1907)
although they don’t actually identify the poliovirus, Dr. Karl Landsteiner and Dr. Erwin Popper identify that a virus causes polio when they inject material from the spinal cord of a child who had recently died with polio into the peritoneum of two monkeys, both of which soon developed paralytic polio (1908)
Simon Flexner, first discovers polio antibodies (1911), but unlike other researchers at the time, pushes the theory that polio was spread by the olfactory route, instead of the fecal-oral route, which was why we saw the development of nose sprays, etc., to try and prevent polio, none of which worked of course
a large polio epidemic in the United States causes at least 27,000 cases and 6,000 deaths (1916)
Philip Drinker and Louis Agassiz Shaw invent the first iron lung, the Drinker respirator (1929)
Frank M. Burnet and Jean Macnamara proposed that there were antigenically different strains of poliovirus (1931)
John R. Paul and James D. Trask help figure out how polio was spread by identifying the polio virus in human waste and sewage samples (1932)
Maurice Brodie and John Kolmer have unsuccessful field trials of early polio vaccines, including allergic reactions and vaccine induced polio because of poor attenuation (1935)
Sister Elizabeth Kenny establishes a clinic in Australia to treat polio survivors (1932) and later publishes her treatment recommendations, Infantile Paralysis and Cerebral Diplegia (1937)
the National Foundation for Infantile Paralysis is founded by FDR to stop polio (1937)
Carl Kling found traces of the poliovirus in the Stockholm sewage system (1942)
the Sister Kenny Institute is built in Minneapolis, as her treatment methods become widely accepted after years of controversy (1942)
the U.S. Army Neurotropic Virus Commission, including Albert Sabin, gets a grant from the NFIP to study polio in North Africa (1943)
Isabel Morgan actually developed the first inactivated polio vaccine, but only tested it on monkeys (1949)
John Enders, with T. H. Weller and F. C. Robbins, received the Nobel Prize in 1954 for their work on the cultivation of the poliomyelitis viruses (1949)
David Bodian creates the monkey model using field isolates of poliovirus and with Jonas Salk, identifies the three poliovirus serotyes (1950s)
Hilary Koprowki develops the first oral, live polio vaccine, (1950) although Sabin’s vaccine eventually gets licensed because it is thought to be less neurovirulent in monkeys and undergoes more testing
there are 58,000 cases of paralytic polio in the United States (1952)
Renato Dulbecco, with Marguerite Vogt, successfully grows and purifies polio virus (1952)
the Polio Pioneers vaccine field trial, led by Thomas Francis Jr., that proves that Jonas Salk’s polio vaccine is safe and effective begins (1954)
the WHO Western Pacific Region is declared polio free (2000)
the United States switches back to using the an inactivated polio vaccine because of concerns over VAPP (2000)
the WHO European Region is declared polio free (2002)
outbreak of vaccine derived polio among a group of unvaccinated Amish in Minnesota (2005)
last case of VAPP that was acquired outside the United States, an unvaccinated 22-year-old U.S. college student who became infected with polio vaccine virus while traveling in Costa Rica in a university-sponsored study-abroad program (2005)
last case of VAPP, a patient with a long-standing combined immunodeficiency who was probably infected in the late 1990s (2009)
Bob Sears says that it is okay to delay the polio vaccine on his alternative vaccine schedule because “we don’t have polio in the United States” (2015)
a global switch from trivalent OPV to bivalent OPV in routine immunization programs (2016)
polio remains endemic in just three countries, Afghanistan, Nigeria, and Pakistan (2018)
So it should be clear, that despite what some folks think, polio wasn’t conquered overnight. And Salk and Sabin obviously had a lot of help, although those are the names we most commonly hear connected with polio eradication.
“Until poliovirus transmission is interrupted in these countries, all countries remain at risk of importation of polio, especially vulnerable countries with weak public health and immunization services and travel or trade links to endemic countries.”
Global Polio Eradication Initiative on Endemic Countries
It is well known that you can very rarely develop polio after being vaccinated with the oral polio vaccine.
VAPP or vaccine-associated paralytic polio are cases of polio that are actually caused by the polio vaccine. That’s why many countries switch over to the inactivated form of the polio vaccine once polio is under good control.
But can you get polio after an injection?
What is Provocation Polio?
You are probably thinking, sure, if the injection is full of live polio virus, right?
But this is actually the idea behind provocation polio.
No, the injection doesn’t give you polio, but if you are already infected with polio, the idea is that getting an injection could be a risk factor for developing paralytic polio.
“Provocation poliomyelitis describes the enhanced risk of paralytic manifestations that follows injection in the 30 days preceding paralysis onset.”
Remember, most people with polio don’t actually have any symptoms, although some do have flu-like symptoms. And fewer than 1% develop paralysis or weakness when they have polio. Although that doesn’t sound like a lot, during a polio epidemic, when a lot of kids are getting polio, the cases of paralytic polio quickly add up.
What else can provoke paralytic polio?
strenuous exercise (paralytic polio)
tonsillectomy (bulbar polio)
So how does an injection provoke paralytic polio?
“Skeletal muscle injury induces retrograde axonal transport of poliovirus and thereby facilitates viral invasion of the central nervous system and the progression of spinal cord damage.”
Gromeier et al on Mechanism of Injury-Provoked Poliomyelitis
Injury to a muscle by the needle is thought to have allowed the polio virus to move through the nerves in the area to the spinal cord, as long as the polio virus was already in their blood. How do we know it was the needle and not the vaccine itself? In experiments, they injected saline, and not an actual vaccine.
Is this how everyone developed paralytic polio?
Remember, kids didn’t get many vaccines around the time we were seeing polio outbreaks in the 1940s and 50s, although other injections, like penicillin were also thought to provoke paralytic polio.
Why were they getting penicillin? Often to treat congenital syphilis.
And although they went so far as to delay vaccines during outbreaks and to not do tonsillectomies during the summer, when polio outbreaks were more common, kids still got paralytic polio.
Could Provocation AFM Be a Thing?
Have you guessed why some folks are talking about provocation polio again, even though we are on the verge of eradicating polio?
“Seizing on a 2014 historical perspective piece on a phenomenon known as “polio provocation” in the highly respected medical journal, The Lancet, anti-vaccine forces have attempted to link the recent AFM cases (as they attempt to do with many other medical occurrences) to childhood vaccinations.”
Dr. Amesh Adalja on Clusters of polio-like illness in the US not a cause for panic
“…is there any relationship between vaccination status and a developing acute flaccid myelitis? Meaning, are vaccines a risk factor? And the data so far says no, the overwhelming number of children who have gotten AFM have had no recent vaccination of any kind or vaccine exposure. These cases over these years have been happening before flu season and flu vaccination starts, which is one of the questions that comes up, and there hasn’t been any pattern to vaccine exposure of any kind in developing AFM. So far, we have not found a link between the two.”
Benjamin Greenberg, MD on 2018 Podcast on Acute Flaccid Myelitis
For vaccines to provoke AFM, you would have to have gotten a recent vaccine.
We aren’t seeing that and anything else all of the kids with AFM had in common that might provoke paralysis, like acupuncture, cupping, or dry needling, would likely have come out in epidemiological reports.
As most folks know, neither the DPT nor OPV vaccines are used in the United States.
That they are still used in other countries likely raises some questions for those folks that get them.
Why Are the DPT and OPV Vaccines Still Used in Some Countries?
As I am sure you have guessed, there is no conspiracy about the continued use of these vaccines in other parts of the world. We aren’t getting rid of old stocks of vaccines or using cheaper vaccines in poorer parts of the world.
So what’s the reason?
To understand why they are still used in other countries, it helps to understand why they aren’t used here.
Remember that the DPT vaccine, which protects folks against diphtheria, pertussis, and tetanus, came under attack in the 1970s and 80s as some folks blamed the vaccine for causing vaccine injuries, including seizures and encephalopathy. It didn’t, but we still got a new vaccine, DTaP, which doesn’t seem to work as well.
“Although concerns about possible adverse events following their administration have led to the adoption of acellular pertussis vaccines in some countries, whole-cell pertussis vaccines are still widely produced and used globally in both developed and developing countries. Whole-cell pertussis vaccines that comply with WHO requirements, administered according to an optimal schedule have a long and successful record in the control of whooping cough. Furthermore, the excellent efficacy of some currently available whole-cell pertussis vaccine has also been shown, not only in recent clinical trials, but also on the basis of the resurgence of disease where vaccination has been interrupted or when coverage has markedly decreased. Therefore, WHO continues to recommend whole-cell pertussis vaccines for use in national immunization programmes.”
WHO on Recommendations for whole-cell pertussis vaccine
The WHO now recommends that if countries do switch to DTaP, the acellular pertussis vaccine, they should be prepared to add additional periodic booster doses and immunizations during pregnancy, which may still “may not be sufficient to prevent resurgence of pertussis.”
The OPV vaccine, on the other hand, was replaced because it can rarely cause vaccine-associated paralytic polio (VAPP) and circulating vaccine-derived polio virus (cVDPV). Of course, it does it at much lower rates than wild polio virus, so until polio is well controlled, the benefit of using OPV outweighs the risk. In addition to being less expensive and easier to use, OPV has the benefit over IPV of providing better herd immunity.
At some point, as we did in the United States in 2000, countries make a switch to the IPV vaccine.
In 2016, remaining countries that use OPV switched from trivalent OPV to bivalent OPV, because wild polio virus type 2 was eradicated in 1999. Once the remaining two types are eradicated, we can stop using the OPV vaccine altogether.
Until then, countries either use:
OPV plus one dose of IPV
sequential IPV-OPV schedules – high vaccine coverage and low risk of wild polio importation
IPV only schedules – sustained high vaccine coverage and very low risk of wild polio importation
So there is no conspiracy. These vaccines are safe and they work.
“All members of the household should wash their hands after changing the diaper of an infant. This minimizes rotavirus transmission, for an undetermined number of weeks after vaccination, from an infant who received rotavirus vaccine.”
General Recommendations on Immunization Recommendations of the Advisory Committee on Immunization Practices (ACIP)
If you wash your hands when you change your child’s diapers after they have been vaccinated, just like you hopefully do anyway, you can avoid any possible contact with any rotavirus vaccine virus that might be shed in your child’s stool.
Can I Get Rotavirus from My Recently Vaccinated Baby?
But what would be the risk of your getting sick if you did come into contact with shedding rotavirus vaccine virus in your child’s diaper?
Would you be at risk to get sick?
Did your baby get sick after getting the actual vaccine?
That’s the thing about shedding that many people don’t understand. These live vaccines are made with attenuated or weakened strains of viruses, so they don’t typically get you sick when you are vaccinated. And they don’t typically get you sick when you are exposed through shedding. In fact, this shedding can sometimes help build herd immunity, as more people get exposed to the weakened strain of vaccine virus.
But can they get you sick?
Yes, if you have a problem with your immune system, which is why there are warnings about giving live vaccines to folks who are immunocompromised. And there used to be warnings about giving the oral polio vaccine to kids if they were around anyone with an immune system problem.
Vaccine viruses could also get you sick if they mutated from their attenuated state and became more virulent. Fortunately, that rarely happens with most vaccines.
“The theoretical risk of HRV and PRV shedding, transmission to, and infection of immunocompromised contacts is much lower than the real risk of wildtype rotavirus infection transmitted from unvaccinated children.”
Anderson on Rotavirus vaccines: viral shedding and risk of transmission
And most importantly, since kids are much more likely to shed virus after natural infections, it is much safer for everyone to get vaccinated and protected with these vaccines.
Surprisingly, even children with asymptomatic natural rotavirus infections can shed virus for several weeks, which is likely why these infections used to spread so easily or without known contacts.
Something that will likely surprise some folks even more is the news that just because someone gets diarrhea after being exposed to the rotavirus vaccine, either because they were vaccinated or through shedding, it doesn’t mean that the vaccine was the cause of the diarrhea!
“Of note, among all six AGE cases which possessed Rotarix-derived strains, four (sample No.1, 5, 6 and 7) were suspected to be caused by other pathogens. Most likely, the infants were infected with other pathogens during the shedding period of Rotarix strain.”
Kaneko et al on Identification of vaccine-derived rotavirus strains in children with acute gastroenteritis in Japan, 2012-2015
When vaccine strain rotavirus have been detected in kids with gastroenteritis, they often have other reasons to have diarrhea.
What does this all mean?
Don’t believe all of the hype anti-vaccine folks push about shedding from vaccines.
Remember, shedding occurs when an infectious agent, typically a virus, can be found in urine, stool, or other bodily secretions. Shedding is not specific to vaccines though. Shedding occurs very commonly after natural infections too, which is one reason they are so hard to control.
So does the Flumist vaccine shed?
Yes, it does, and it isn’t a secret.
There is actually a warning about shedding and Flumist – to avoid contact with severely immunosuppressed persons (e.g., hematopoietic stem cell transplant recipients in a protected enviornment) for seven days after vaccination because of the theoretical risk that their severe immunosuppression might allow the weakened flu strain to somehow cause disease.
This warning obviously doesn’t apply to the great majority of people though.
And it shouldn’t be surprising that it sheds, after all, it is a live virus vaccine that is squirted in your nose!
Why isn’t it usually a problem?
Flumist contains attenuated viral strains of the flu that are temperature-sensitive, so even if you did get infected with the weakened flu strains from Flumist via shedding, they wouldn’t cause disease.
Another way to think about it is that the folks who actually get the Flumist vaccine don’t get the flu, so why would you get the flu if you were simply exposed to the vaccine virus by shedding?
The real concern with shedding is when it leads to folks actually getting sick.
Trying to scare folks about Flumist shedding is just like when they talk about the MMR vaccine, pushing the idea that the rubella vaccine virus might shed into breast milk or measles vaccine virus into urine. Either might happen, but since it won’t cause infection and disease, it certainly isn’t a reason to skip or delay your child’s vaccines.
What to Know About Shedding and Flumist
The Flumist vaccine does indeed shed, but unless you are going to have contact with someone who is severely immunocompromised in a protected environment, this type of shedding isn’t going to get anyone sick and isn’t a reason to avoid this vaccine.