Tag: polio vaccines

Is Polio Returning to Venezuela?

Breaking News – further tests have found that the person with suspected polio did not have either wild polio or vaccine-derived poliovirus (VDPV). Could it still be polio? (see below).

Polio is on the verge of being eradicated.

In 2017, there have only been 118 cases of polio in the whole world, including 22 cases of wild poliovirus in Afghanistan and Pakistan and 96 cases of vaccine-derived poliovirus (VDPV) in the Democratic Republic of Congo and Syria.

So far this year, there have only been 15 cases of polio in the whole world, including 10 cases of wild poliovirus in Afghanistan and Pakistan and five cases of vaccine-derived poliovirus (VDPV) in the Democratic Republic of Congo and Nigeria.

Is Polio Returning to Venezuela?

Most of us are aware that vaccine-preventable diseases are just a plane ride away.

We see it, or at least read about it, all of the time, as we continue to see outbreaks of measles affecting our communities.

But polio?

Could polio return?

Venezuela has been polio free for nearly 30 years. The last case of a wild poliovirus infection was in March 1989. And yet ,there are now thought to be at least four cases of poliovirus, type 3 in the Delta Amacuro state of north east Venezuela, where they are also seeing cases of diphtheria and measles.

Report of polio in Venezuela

Among the polio cases is a 2-year-old boy who was unvaccinated, an unvaccinated child who lived next to him, and a partially vaccinated child 8-year-old who lived next door.

“It has been reported unofficially that it is polio vaccine virus.”

Venezuelan Society of Public Health Report

But what is the source of the polio vaccine virus?

We supposedly stopped using oral polio vaccines that can shed in January 2016, right?

Actually, we began the switch from trivalent OPV (tOPV) to bivalent OPV (bOPV) in 2016, removing the the type 2 polio virus that is most likely to cause VAPP. Making sure kids get a dose of IPV first also lowers the risk of VAPP. At least it does when kids get vaccinated according to plan.

“Other children from the same community were vaccinated in April 2018 with oral bivalent polio vaccine.”

PAHO on Epidemiological Update Detection of Sabin type 3 vaccine poliovirus in a case of Acute Flaccid Paralysis 

When did the first case appear? Although we are just hearing about it now, his symptoms began in April, right around the time another child received a bivalent oral polio vaccine.

“No additional AFP cases have been identified to date through active search for AFP cases carried out in the community.”

PAHO on Epidemiological Update Detection of Sabin type 3 vaccine poliovirus in a case of Acute Flaccid Paralysis 

Fortunately, in the past month, no further cases have been identified.

Children in Venezuela are supposed to get at least one dose of IPV (inactivated polio vaccine), followed by four doses of bOPV (bivalent oral polio vaccine).
Children in Venezuela are supposed to get at least one dose of IPV (inactivated polio vaccine), followed by four doses of bOPV (bivalent oral polio vaccine).

So what does this all mean?

For one thing, wild polio isn’t returning to Venezuela. And it doesn’t look like we will see a large outbreak of cVDPV, as there are no further cases of AFP in the area.

But it does illustrate that we can easily see a return of vaccine-preventable disease if we don’t keep vaccinating until they are eradicated. Remember, low vaccination coverage is associated with outbreaks of cVDPV. If everyone is vaccinated and protected, then they won’t get polio, whether it is wild type or shed from someone who was vaccinated.

Latest Updates on AFP in Venezuela

While a Sabin type 3 polio virus had been initially isolated from the stool samples of the unvaccinated 34-month-old boy with polio symptoms, further tests have now been completed.

“Tests carried out by the specialized global laboratory for genetic sequencing have ruled out the presence of both wild poliovirus and vaccine-derived poliovirus (VDPV). The latter- VDPV- is a Sabin virus with genetic mutations that give it the ability to produce the disease. There is no risk of spread to the community or outbreaks of polio from this case.”

PAHO

So what does he have?

The possibilities are non-polio AFP, as many viruses and other diseases can cause polio-like symptoms.

So why did he have the Sabin type 3 polio virus in his stool?

It is well known that the oral polio vaccines shed. Even though he was  unvaccinated, he was likely exposed to others in the community who were recently vaccinated, as it is possible to shed the vaccine virus in your stool. The attenuated (weakened) vaccine virus is unlikely to cause symptoms though, unless it develops the mutations found in VDPV strains, which this one didn’t.

“The child is being further evaluated clinically to determine alternative causes of paralysis. The final classification of the case of acute flaccid paralysis [to define whether or not it is associated with the vaccine] will be based on clinical and virological criteria assessed at 60 days after the onset of paralysis.”

PAHO

So despite what folks are reporting, they didn’t say that this case couldn’t be associated with the polio vaccine. We just know that it is isn’t wild polio and the virus doesn’t have the mutations associated with cVDPV strains, which can not only cause polio symptoms, but can also spread from one person to another, causing outbreaks.

Remember, although the attenuated vaccine virus in the oral polio vaccine is unlikely to cause polio symptoms, it sometimes can, in about 1 in 2.7 million doses.

“VAPP at this time can’t be ruled out, of course, as it’s one of the possibilities.”

Communications Officer
Global Polio Eradication Initiative

Could this child have VAPP?

“A VAPP case was most often defined as a case of acute flaccid paralysis (AFP) with residual paralysis (compatible with paralytic poliomyelitis) lasting at least 60 days, and occurring in an OPV recipient between 4 and 40 days after the dose of OPV was administered, or in a person who has had known contact with a vaccine recipient between 7 and 60–75 days after the dose of OPV was administered.”

Platt et al on Vaccine-Associated Paralytic Poliomyelitis: A Review of the Epidemiology and Estimation of the Global Burden

I guess we will find out in a few weeks, as his symptoms started at the end of April.

Still, remember that VAPP is not contagious.

What to Know About Polio Returning to Venezuela

Several cases of a vaccine strain of polio virus have been found in Venezuela, which is linked to low vaccinated levels.

More on Polio Returning to Venezuela

Updated June 17, 2018

Is There a DDT-Polio Connection?

Polio is caused by one of three wild-type polio viruses.

Of course, anti-vaccine folks like to push misinformation about polio being caused by a lot of other things, from poor hygiene and eating too much white bread to having a tonsillectomy or being exposed to pesticides, like DDT.

“Williams describes the many blind alleys and false leads of the early days of polio research, when doctors, scientists, and public health officials were convinced that the disease was transmitted by bedbugs, budgies, cats, and flies, or caused by seafood, cow’s milk, jimson weed, fruit, vegetables, and DDT…”

Paul Offit on Polio Revisited

Not surprisingly, it is DDT that they like to focus on the most.

They even have graphs that they think correlate the rise in production of DDT with an “Age of Polio.”

Polio Is Good For Meeee!

First things first though.

Why do anti-vaccine folks want to connect DDT and polio?

It’s simple.

If the polio virus doesn’t cause polio (germ theory denialism), then you can’t really expect the polio vaccine to prevent polio, now can you?

The DDT-Polio Connection?

There actually is a bit of a connection between polio and DDT, but not the one anti-vax folks think.

Wait, what?

No, DDT didn’t cause polio.

“Between the end of World War II and the early 1950s, researchers, municipal officials, and individuals from Georgia to California employed DDT to stop polio by killing flies, a suspected but debated actor in the disease’s transmission.”

Conis on Polio, DDT, and Disease Risk in the United States after World War II 

Yes, many towns would routinely spray with DDT after a polio epidemic came to town because they didn’t yet know what did cause polio.

For example, in May 1946, “sections of the city were blanketed” with DDT as they sought to stop the source of a polio epidemic in San Antonio, which they thought might be a “tropical mosquito.”

Even the schools were closed in San Antonio when polio came to Texas in 1946.
Even the schools were closed in San Antonio when polio came to Texas in 1946. And they stayed closed for the last few weeks of the Spring term!

See the connection now?

Polio first. DDT spraying after.

This idea is especially easy to see when you understand that there were many polio outbreaks and epidemics in the late 19th and early 20th century, well before DDT was discovered to be an effective insecticide in the early 1940s.

And the spraying mostly stopped before the polio outbreaks stopped.

In 1951, although he wasn’t yet sure how the polio virus spread, Dr. Sabin did know it came from “human feces derived from patients and healthy carriers,”  and he declared that there was “general agreement that there is no justification for initiating emergency insect control measures in the hope of stopping a poliomyelitis epidemic.”

“It is perhaps an established epidemiological principle that epidemiological probability must be compatible with bacteriologic (or virologic) possibility, particularly when the epidemiological probabilities lend themselves to several alternative explanations.”

Albert B Sabin, MD on Transmission of Poliomyelitis Virus

And even before that, the Editorial Board for the American Journal of Public Health, in 1946, said that “While municipal cleanliness and sanitation are always highly desirable, there is no reason to believe that improved methods of sewage treatment and disposal, more rigid standards for the purification of water supplies, or the dusting of DDT over a city from aeroplanes will have any measurable effect on the incidence of infantile paralysis.”

Also remember the other big reason that we saw DDT spraying in the United States – the elimination of malaria.

“The National Malaria Eradication Program, a cooperative undertaking by state and local health agencies of 13 southeastern states and the CDC, originally proposed by Louis Laval Williams, commenced operations on July 1, 1947. By the end of 1949, over 4,650,000 housespray applications had been made.”

CDC on Elimination of Malaria in the United States (1947 — 1951)

Did the spraying of DDT to eliminate the flies that transmit malaria in the southeastern United States correlate with extra cases of polio?

No.

There were big outbreaks in New York, Indiana, Ohio, and many other parts of the country that didn’t spray DDT to help fight malaria.

“The peak year for use in the United States was 1959 when nearly 80 million pounds were applied. From that high point, usage declined steadily to about 13 million pounds in 1971, most of it applied to cotton.”

EPA on DDT Ban Takes Effect

Did we stop spraying with DDT in the early 1950s because it was banned and is that why we stopped seeing so much polio?

No.

The peak year for DDT use was in 1959. Surprisingly, we don’t see that peak on any anti-vaccine graphs in 1959…

What was the peak year for polio cases? It wasn’t 1959 or 1960, as you would expect if there was a link between DDT and polio.

The peak year for polio cases was in 1952.

Although the use of DDT decreased after 1959, it was used until it was “banned” in 1972, and even then, there were exceptions for public health uses.

Explaining Polio

The polio virus causes polio.

But why?

Or at least why did we start seeing so many more cases in the late 18th through the mid 19th century, until it was controlled with our polio vaccines?

“…contrary to the prevailing “disease of development” hypothesis, our analyses demonstrate that polio’s historical expansion was straightforwardly explained by demographic trends rather than improvements in sanitation and hygiene…”

Martinez-Baker et all on Unraveling the Transmission Ecology of Polio

One rather simple and elegant explanation is that we started to get too clean, the “disease of development” hypothesis.

Improved hygiene and sanitation helped delay when kids would get polio. Remember, polio is spread by contaminated food and water through fecal-oral transmission.

So instead of routinely getting it when they were newborn babies or young infants, when they still had some protection from maternal antibodies, they got it later when they had no immunity. So polio essentially changed from an endemic disease, or something that everything got, to an epidemic form.

And now, despite the work of the anti-vaccine movement, it will hopefully soon become an eradicated form!

What to Know About The DDT-Polio Connection

DDT is a pesticide that was widely used after World War II and was sometimes sprayed in a vain attempt to keep polio outbreaks from getting out of control. That is the only connection to polio though.

More About The DDT-Polio Connection

 

How Quickly Can You Debunk Anti-Vaccine Propaganda?

It is well known that much of the stuff on anti-vaccine websites is pure misinformation that is simply put out there to scare parents away from vaccinating and protecting their kids.

At least it is well known by the people who understand that vaccines are safe, vaccines are necessary, and that vaccines work.

If you are on the fence or hesitant to vaccinate your kids, you might not be so sure and might not know who to trust when it comes to getting information about vaccines.

That’s why it is important to get educated, be skeptical, and do your own research.

How Quickly Can You Debunk Anti-Vaccine Propaganda?

What do you think about the following photo description that is making the rounds on anti-vaccine websites and on Facebook?

How quickly could you figure out if the information is true or not?

Is this a photo of kids in iron lungs because of the Cutter Incident?
Is this a photo of kids in iron lungs because of the Cutter Incident?

Of course, the Cutter Incident is actually true and plenty of folks ended up in iron lungs, mostly because of natural polio infections though, not because of the polio vaccine.

“In 1952 alone, nearly 60,000 children were infected with the virus; thousands were paralyzed, and more than 3,000 died.”

Jason Beaubien on Wiping Out Polio: How The U.S. Snuffed Out A Killer

Let’s start doing some research…

The first clue that this isn’t real is that the cases from the Cutter Incident would have been spread out over the five Western and mid-Western USA states where kids got this particular polio vaccine. With about 200 of them severely affected, they almost certainly would not have had such a large group of people in iron lungs, enough to fill a gymnasium, in just one area.

The next clue is that the iron lungs aren’t plugged in.

That led me to a quick search for ‘iron lung photos’ and an article on Understanding Historical Photos that features the iconic “Iron lungs in gym” photo.

“At first glance, this image shocks and saddens from the enormity of the problem of sick children in need of iron lungs. On closer examination, it is clear that the equipment that usually accompanied people using iron lungs, such as tracheotomy tubes and pumps and tankside tables, is not present (compare the picture to photographs in the section on the iron lung). This scene was staged for a film. It is not historically accurate as a respirator ward, but is an example of an established photographic technique (famously used, for example, by WPA photographers in the 1930s) of directing the viewer’s response by creating a shot that would not naturally occur. ”

Smithsonian National Museum of American History on Understanding Historical Photos

A little more research helped me discover that the photo was taken:

  • for an informational film that was being produced by the March of Dimes
  • in the auditorium of the Rancho Los Amigos National Rehabilitation Center in Downey, California USA
  • in 1953

So it took less than a few minutes to figure out that the folks who claim to be “exposing the truth” about vaccines are pushing pure propaganda.

Remember, the Cutter Incident happened in 1955, two years after this photo was taken…

So, a staged 1953 photo for an informational movie for the March of Dimes does not show kids in iron lungs from the Cutter Incident!

How long would you have believed this or other polio myths?

How long would it take you to debunk them?

What to Know About Debunking Anti-Vaccine Propaganda

Learn just how quickly most anti-vaccine misinformation can be debunked if you simply practice being a little skeptical and do your own research.

More About Debunking Anti-Vaccine Propaganda

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Who Is Robin Cavendish?

Polio is close to being eradicated.

So far this year, there have only been 11 cases of wild polio in the world – 6 in Afghanistan and 5 in Pakistan.

“In 1952 alone, nearly 60,000 children were infected with the virus; thousands were paralyzed, and more than 3,000 died.”

Jason Beaubien on Wiping Out Polio: How The U.S. Snuffed Out A Killer

Robin Cavendish was born and raised in the pre-vaccine era though, before we had the polio vaccines that have controlled, and will hopefully soon eradicate, polio.

Who Is Robin Cavendish?

Breathe is the story of Robin and Diane Cavendish.
Breathe is the story of Robin and Diana Cavendish.

Robin Francis Cavendish was born on March 12, 1930 in Middleton, Derbyshire, England.

After an early career in the Army, he helped start a tea-brokering business in Africa and made frequent trips to Kenya.

It was in Kenya that he developed paralytic polio in December 1958, just over three years after Jonas Salk‘s polio vaccine was found to be effective in field trials (April 1955).

Although he was initially given just three months to live after his diagnosis, with the help of his wife Diana, he was able to survive for another 36 years!

And they did a lot with those years, including:

  • using a specially adapted van to travel around England
  • developing a wheelchair with a built-in respirator with their friend, Oxford professor Teddy Hall and his company Littlemore Scientific Engineering. Their first prototype of their portable respirator was released in 1962 – the Cavendish Chair.
  • helping scientists develop the Possum, a device that helped severely disabled people electronically control their environment, including answer the phone or turn on the TV
  • becoming an advocate for other polio survivors
  • co-founding the charity Refresh with Dr. Geoffrey Spencer, which started as a way for families who needed extra help because of the need for a respirator to go on vacation together

The story of his remarkable life is told in the new movie Breathe.

And while it is also a great reminder of what life was like before we had vaccines, we shouldn’t forget about all of the other polio survivors, some of whom now have to deal with post-polio syndrome.

Nor the fact that we are so close to ending polio. Or at least new polio infections.

What to Know About Robin Cavendish

Robin Cavendish was a respirator dependent polio survivor whose life story is told in the new movie Breathe.

More About Robin Cavendish and Surviving Polio

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Myths About Polio and Acute Flaccid Paralysis

Polio is one of the most well known causes of acute flaccid paralysis.

Although most people with polio infections have no symptoms at all, or just have a very mild illness, with a sore throat and a low grade fever, a small percentage can develop:

  • a loss of superficial reflexes
  • severe muscle aches and spasms in their limbs or back
  • an asymmetrical flaccid paralysis with diminished deep tendon reflexes

This acute flaccid paralysis only affects the child’s strength in the affected muscle groups – there is no loss of sensation. The severity of the symptoms and the disease depends on which muscles are affected the most. If it is just your legs, then you will have trouble walking. On the other hand, if it affects your chest, then you might not be able to breath, unless you are put on a ventilator (iron lung).

Acute Flaccid Paralysis

Thinking about it in the context of polio, it becomes easy to understand acute flaccid paralysis or AFP.

It is the sudden onset (acute) of a flaccid (floppy or poor muscle tone) paralysis (weakness or inability to move) of one or more muscles.

But what many people don’t understand, is that in addition to polio, there are many more non-polio causes of AFP.

Non-Polio AFP

Many of us got a crash course in non-polio acute flaccid paralysis (NP-AFP) a few years ago when we started hearing reports of kids developing polio-like paralysis in 2014. Now thought to be caused by enterovirus D68 infections (EV-D68), the paralysis followed respiratory tract infections in many of the affected children. All together, at least 120 children in 34 states developed acute flaccid paralysis that year.

Interestingly, EV-D68 is one of more than 100 non-polio enteroviruses. The virus that causes hand, foot, and mouth disease, coxsackievirus A16, is another. Others cause pinkeye, meningitis, or encephalitis.

Keep in mind that many other viruses and conditions can cause non-polio AFP too, including:

  • Guillian-Barré syndrome
  • toxins (botulism)
  • tumors
  • transverse myelitis
  • traumatic neuritis
  • other infections, including novel enterovirus C105, a non-polio enterovirus, and even tick-borne (Lyme disease) and mosquito-borne (Japanese encephalitis) infections

How do you determine the cause and how do you know it isn’t polio?

These kids with AFP typically have extensive testing to determine what is causing their AFP, including an MRI, antibody tests, and testing of their cerebrospinal fluid, etc. Although it isn’t always possible to identify a cause, you can at least rule out many potential suspects, like trauma, polio, and other infections.

Myths About Polio and Acute Flaccid Paralysis

Some folks don’t believe in non-polio AFP.

They believe that polio never really disappeared because vaccines don’t really work and that polio was simply renamed to, you guessed it, acute flaccid paralysis.

“Unbeknownst to most doctors, the polio-vaccine history involves a massive public health service makeover during an era when a live, deadly strain of poliovirus infected the Salk polio vaccines, and paralyzed hundreds of children and their contacts. These were the vaccines that were supposedly responsible for the decline in polio from 1955 to 1961! But there is a more sinister reason for the “decline” in polio during those years; in 1955, a very creative re-definition of poliovirus infections was invented, to “cover” the fact that many cases of ”polio” paralysis had no poliovirus in their systems at all. While this protected the reputation of the Salk vaccine, it muddied the waters of history in a big way.”

Suzanne Humphries, MD on Smoke, Mirrors, and the “Disappearance” Of Polio

What’s their evidence?

A rise in cases of non-polio AFP in India since 1997.

How do we know that there has been a rise in non-polio AFP cases in India since 1997?

It’s very simple and explains why there isn’t any data on before that 1997. 

As part of the strategy to eliminate polio in that country, starting in 1997, all cases of AFP started getting tested for polio. It was a way to track the effectiveness of the immunization program. If you were seeing too many cases of AFP caused by polio, then not enough people were getting vaccinated. On the other hand, if you weren’t seeing any cases of AFP in an area, then the testing and surveillance probably wasn’t getting none, since there will always be some cases of non-polio AFP.

Unfortunately, they found many cases to track. And the cases kept increasing, although more and more, they weren’t being caused by polio. At least not by live polio virus.

Were they caused by the polio vaccine?

In some cases, yes. It is well known that the live polio vaccine can rarely cause VAPP and cVDPV.

By 2015, after India was declared free of polio (the last case was in 2011), none of those cases of AFP were found to be caused by wild polio though. And India hasn’t had a case of cVDPV since 2010.

Why the increase in cases of non-polio AFP? It certainly isn’t because of Suzanne Humphries’ polio virus renaming conspiracy or any other anti-vaccine conspiracy involving the polio vaccine itself.

The 'data' that Susanne Humphries uses to try and make her case about AFP neglects to mention that in the pre-vaccine era, polio paralyzed 500 to 1,000 children in India each day! Those 180,000 to 365,000 cases of paralysis wouldn't fit on her chart though...
The ‘data’ that Susanne Humphries uses to try and make her case about AFP neglects to mention that in the pre-vaccine era, polio paralyzed 500 to 1,000 children in India each day! Those 180,000 to 365,000 cases of paralysis wouldn’t fit on her chart though…
If we simply renamed polio to non-polio AFP, why did the numbers drop for so long and then slowly start to increase? Shouldn’t it have been a rapid crossover?

More importantly,  why are the case of paralysis from non-polio AFP so much lower than the pre-vaccine era cases of AFP from polio?

And how come we rarely see large outbreaks of AFP like we did in the pre-vaccine era?

Sure, 120 kids in the EV-D68 non-polio AFP outbreak of 2014 is way more than any of us would like to see, but it is tremendously less than what we used to see in the pre-vaccine era from polio.

“Poliomyelitis is one of the important emergent viral diseases of the twentieth century… At its height, from 1950–1954, poliomyelitis resulted in the paralysis of some 22,000 U.S. citizens each year… Many thousands were left permanently disabled by the disease, while many others suffocated as a consequence of respiratory paralysis.”

Barry Trevelyan on the The Spatial Dynamics of Poliomyelitis in the US

While anti-vaccine conspiracy theories about AFP are as easy to dismiss as all of the rest they bring up,  what is behind the rise in AFP in some areas of the world?

Although one study that was published in Pediatrics, “Trends in Nonpolio Acute Flaccid Paralysis Incidence in India 2000 to 2013,” did find a correlation between the use of the OPV vaccine and the incidence of non-polio AFP, many experts think the rise is a result of better screening. Also, once polio gets under control, other more neglected diseases start getting more attention, like enteroviral infections. Not surprisingly, other parts of the world have had the same experience.

There is also the fact that in 2005, the Global Poliomyelitis Eradication Initiative began “to cast a wider net for poliovirus detection and to maximize sensitivity so that every poliomyelitis case is detected.” Why? If even a single case was missed, it could lead to continued outbreaks and would get in the way of polio elimination in the country.

“This large increase in NP-AFP cases, which represent AFP cases caused by agents other than poliovirus, probably reflects the excellent implementation of the expanded definition of AFP and highly sensitive surveillance and detection methods used by NPSP in India from 2005 onwards…”

C. Durga Rao on Nonpolio Acute Flaccid Paralysis in India

So did the polio vaccine recently cause 53,000 paralysis victims in India?

No. 

The polio vaccine has worked to get us on the brink of eradicating polio though.

What To Know About Acute Flaccid Paralysis

Acute flaccid paralysis can be caused by the polio virus, but non-polio acute flaccid paralysis becomes a more important cause once polio is eliminated in a region.

More About Acute Flaccid Paralysis

cVDPV

Circulating vaccine-derived polio virus or cVDPV are outbreaks of polio that are actually caused by the polio vaccine.

Very rarely, the attenuated (weakened) virus in the oral polio vaccine can revert to a form that can cause the person who was vaccinated or their close contact to actually develop polio.

It should not be confused with VAPP or vaccine-associated paralytic polio. With VAPP, the original strain of attenuated vaccine virus reverts to a form that can cause polio, but it does spread from one person to another, so does not lead to outbreaks.

cVDPV Outbreaks

Fortunately, both VAPP and cVDPV are rare.

How rare? VAPP only occurs in about 1 in every 1.27 million children receiving their first dose of OPV.

And according to the WHO, there had only been about 24 outbreaks of cVDPV over the past 10 years. Tragically, this has resulted in at least 750 cases of paralytic polio in 21 countries.

An outbreak of cVDPV in Syria will be controlled by 355 vaccination teams that will vaccinate up to 328,000 children.
The WHO reports that an outbreak of cVDPV in Syria will be controlled by 355 vaccination teams that will vaccinate up to 328,000 children.

A new outbreak of cVDPV in Syria adds to those numbers though.

After being polio free for 15 years, since 1999, Syria began having cases of wild type polio again in 2013 (35 cases) and 2014 (1 case). Those polio cases and the emergence of an outbreak of cVDPV2 (there are three strains of polio virus – this outbreak was caused by the type-2 strain) highlight the effects of years of poor immunization rates because of war.

While there are many challenges to getting kids vaccinated in Syria, up to 355 vaccination teams with 61 supervisors will be working out of five vaccine distribution centers to vaccinate 328,000 children to control the outbreak and get kids vaccinated.

Circulating Vaccine-Derived Polio Virus

Just like wild type polio, we can stop cVDPV by increasing vaccination rates and increasing access to improved sanitation facilities.

Why?

Although anti-vaccine folks routinely cry wolf about shedding, the oral polio vaccine really does shed – in the stool of people who have been recently vaccinated. You can then be exposed to the attenuated polio vaccine virus (which can help give immunity to others in the community by passive immunization) or a strain of cVDPV (which can, unfortunately, help give others, especially if they are not vaccinated, paralytic polio) if they are exposed to open sewage or can not practice proper hygiene, etc.

Can’t we just stop using the live, oral polio vaccine?

Although a serious side effect of the vaccine, the vaccine’s benefits clearly outweigh the risk of both VAPP and cVDPV while polio is endemic (lots of cases) in a region, after all, without the vaccine, hundreds of thousands of children would get polio and would be paralyzed.

In polio-free countries, the risks of VAPP and cVDPV becomes greater than the risk of polio though, and they move to the inactivated polio vaccine. That helps prevent a situation in which the polio vaccines actually causes more cases of polio than wild type polio viruses.

Eventually, all countries will move to the IPV vaccine as we move closer to polio eradication. We came one step closer to that point in April 2016 when all countries that were still using the oral polio vaccine switched from trivalent OPV (three strains) to bivalent OPV (two strains) for their routine immunization programs. This could eliminate up to 90% of cases of cVDPV (most are caused by the type-2 strain which is not in bOPV)!

What To Know About cVDPV

Circulating vaccine-derived polio virus outbreaks are a rare side effect of the oral polio vaccine.

More Information About cVDPV