In fact, morbidity/mortality from polio vaccines are decreasing, as we are using much less oral polio vaccine (OPV) in the transition (OPV cessation) to just using inactivated polio vaccine (IPV).
“Over the past ten years, more than 10 billion doses of OPV have been given to nearly three billion children worldwide. More than 16 million cases of polio have been prevented, and the disease has been reduced by more than 99%. It is the appropriate vaccine through which to achieve global polio eradication.”
And while most developed countries already use IPV, those that are still using OPV recently switched from a trivalent (tOPV) to a bivalent (bOPV) form of OPV. We could do this because type 2 poliovirus has already been eradicated (2015)!
So morbidity (getting sick)/mortality (dying) from polio vaccines is low.
What about morbidity/mortality from polio?
“As recently as 30 years ago, wild poliovirus paralysed more than 350 000 children in more than 125 countries every year. In 2018 there were fewer than 30 reported cases in just two countries – Afghanistan and Pakistan.”
“Zero polio transmission and health for all”, WHO Director-General gives new year’s wish to the people of Afghanistan and Pakistan
With a 99.9% drop in polio cases since 1998, your risk of getting polio in most parts of the world is very low, but you still have to consider both the morbidity/mortality of polio in the pre-vaccine era and the risk of polio returning if we stop vaccinating before it is eradicated.
What about the idea that you don’t have to worry about polio because only 1% of kids with polio developed paralysis?
“The mortality rate for acute paralytic polio ranges from 5–15%.”
Disease factsheet about poliomyelitis
Well, when everyone gets polio, even 1% is a lot.
With such a safe vaccine, why put your kids at risk of getting polio?
Do you even understand what the risks are?
No, it isn’t just the risk of wild polio in Afghanistan and Pakistan.
Since the oral polio vaccines shed, if you are unvaccinated, in addition to the risk of wild polio, there is a small risk of getting circulating vaccine-derived polioviruses (cVDPV) if you are not vaccinated and protected. No, it is not a big risk, as there were only 102 cases of cVDPV in 7 countries in 2018, but it isn’t zero either.
And the other big risk is that if enough folks stop getting vaccinated, taking their chances hiding in the herd, polio will come back and our chance to eradicate another vaccine-preventable disease will fail.
More on the Morbidity and Mortality Rates of Polio
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)
last imported case of polio in the United States (1993)
the WHO Region of the Americas is declared polio free (1994)
“last” case of VAPP that was acquired in the United States (1999)
last case of wild poliovirus type 2 (1999)
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 in the United States, 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 two countries, Afghanistan 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