Tag: VAPP

Why Are the DPT and OPV Vaccines Still Used in Some Countries?

As most folks know, neither the DPT nor OPV vaccines are used in the United States.

Pope Francis helped launch a polio vaccine campaign when he visited Mexico in 2016.

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.

Without them, there would be over:

1.3 million pertussis related deaths each year
600,000 cases of paralytic polio each year

With most of these cases affecting young children.

Can I Get Rotavirus from My Recently Vaccinated Baby?

Your two month old recently got her vaccines, including the rotavirus vaccine.

Now you have diarrhea.

Was it from shedding from your child’s rotavirus vaccine?

Does the Rotavirus Vaccine Shed?

Like some other live virus vaccines, it is well known that the rotavirus vaccine can shed.

And like with most other vaccines, this shedding isn’t usually a cause for concern and definitely isn’t a reason to think about skipping or delaying your child’s vaccines.

Why not?

“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.

Does the FluMist Vaccine Shed?

Anti-vaccine folks like to talk a lot about shedding.

Where do they get the idea that vaccines shed?

Well, there is the fact that some live vaccines, like the rotavirus and oral polio vaccine, do actually shed.

Does the FluMist Vaccine Shed?

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?

Shedding from the Flumist vaccine doesn't cause disease. — Anti-vaccine folks are sharing this table like they uncovered some secret, but it is important to understand that shedding from the Flumist vaccine doesn’t cause disease. And this table is in package insert for Flumist!

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 or 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 enviornment, this type of shedding isn’t going to get anyone sick and isn’t a reason to avoid this vaccine.

When is Shedding Season?

Have you heard of shedding season?

I’ll give you a hint, we aren’t talking about cats and dogs…

When is Shedding Season?

So it seems that some folks are really worried about vaccines and shedding.

Precautions against viral shedding? Was he giving out smallpox or oral polio vaccines?

While some vaccines do actually shed, it is really only the oral polio vaccine and the smallpox vaccine that we get concerned about with shedding.

And even then, shedding from the oral polio vaccine would only be a concern for someone with an immune system problem. Since the oral polio vaccine contains an attenuated virus, if that attenuated virus shed to someone else, they wouldn’t get polio except in the very rare situation when the virus mutates. Instead, they would get protection against polio. That’s one of the benefits of using the oral polio vaccine!

Still, we don’t use the oral polio vaccine in the United States anymore.

Although the smallpox vaccine can shed, it is from the site of injection, where a scab forms in the days to weeks after getting vaccinated. Covering the site should prevent other people from getting exposed to shed virus and fortunately, this vaccine is only used in very special situations.

And the rotavirus vaccine sheds, but you just have to wash your hands after changing diapers to avoid this attenuated virus. Are you going to get rotavirus if you are exposed to an infant who was recently vaccinated? Infants who get the vaccine don’t get rotavirus, so why would you if you are exposed to them?

And other vaccines?

While some live vaccines might shed in very specific situations, like if they caused a rare vaccine-induced disease, they otherwise don’t shed. That’s why we don’t worry about most folks with immune system problems getting exposed to people who have recently been vaccinated.

Don’t believe me?

Every time there is an outbreak of measles, someone insists that it was caused by a vaccine strain of measles that was shed from someone who was recently vaccinated. How often is that true?

So when is shedding season?

Anti-vaccine folks consider the start of the school year to be shedding season, because that’s when they think kids get caught up on their vaccines. Is that why we see big outbreaks of measles, chicken pox, and rotavirus at the start of the school year?

Oh wait, we don’t…

“Live vaccine virus shedding is a possible source of transmission of vaccine-strain viral infection but how frequently that occurs is unknown. There is no active surveillance of live virus vaccine shedding and most vaccine strain virus infections likely remain unidentified, untested and unreported.”

NVIC on The Emerging Risks of Live Virus & Virus Vectored Vaccines: Vaccine Strain Virus Infection, Shedding & Transmission

Despite the best efforts of anti-vaccine folks to scare parents about shedding, folks should know that this is no shedding season.

Cases of vaccine strain virus infections from shedding are unidentified and unreported because they don’t happen!

This is why some folks believe in shedding season... — This is why some folks believe in shedding season…

Do you need to teach your kids to fist bump instead of shaking hands during shedding season???

Think about it.

If there were a shedding season, then why wouldn’t there be more outbreaks? Because everyone has learned to fist bump and avoid shaking hands in school?

What to Know About Vaccine Shedding and Shedding Season

Shedding season isn’t a real thing.

Did Modern Ventilators Replace the Iron Lung for Folks with Polio?

Believe it or not, some folks don’t think that vaccines work and that some diseases, like smallpox and polio, never really went away.

Want the real truth? Residual paralysis that lasts more than 60 days is the strongest predictor that a case is really polio, which is why, in addition to testing for polio virus, the 60 day standard is used.

Of course, they have special little theories for how this all works.

Did Modern Ventilators Replace the Iron Lung for Folks with Polio?

In addition to thinking that we just change the names of diseases when we want them to go away, some folks think that we don’t see anyone in iron lungs anymore, not because polio has been eliminated, but because modern ventilators simply replaced the iron lung.

Is that true?

The iron lung, invented in 1927, helped people with polio breath.

In fact, in the 1940s and 1950s, there were whole hospital wards full of polio patients in iron lungs.

Unlike most of today’s ventilators, the iron lung is a negative pressure ventilator. In contrast, most modern ventilators, the ones that you see people hooked up to with a tube going down to their lungs, are positive pressure ventilators.

Iron Lung

What’s the difference?

A positive pressure ventilator pushes air into your lungs. They are useful when you have a lung disease or simply can’t breath on your own.

When people had polio, there usually wasn’t anything wrong with their lungs – it was their chest muscles and diaphragm that were the problem. So the negative pressure in the iron lung would compress and decompress their chest.

One benefit of the iron lung included that it was less invasive than ventilating someone through a tracheostomy, which became an option in the 1960s. While many new options became available for those needing long term ventilation since then, including noninvasive positive pressure ventilation, some still like to use their iron lungs.

Thanks to vaccines, most folks will only see an iron lung in a museum and read about polio in history books. Photo by Oscar Tarragó, M.D., M.P.H.

And while it is true that they don’t make them anymore, iron lungs have not disappeared. There are some folks with polio that still use them.

But what if someone developed polio now, would they be put in an iron lung?

No, they wouldn’t. For one thing, they don’t make iron lungs anymore. Instead, they would likely use mouth intermittent positive pressure ventilation.

Still, we don’t see a lot of folks getting diagnosed with polio, needing to use mouth intermittent positive pressure ventilation, instead of iron lungs these days. And that’s because we don’t see a lot of folks getting diagnosed with polio.

Vaccines work. Polio is almost eradicated.

What to Know About Polio, Modern Ventilators and Iron Lungs

Although some people with polio are still using their iron lungs, the main reason we don’t see more people with polio needing to use iron lungs or modern ventilators is simply because polio is almost eradicated.

Did the US Government Lose a Landmark Vaccine Lawsuit?

Have you heard the big news in the anti-vaccine world?

The anti-vaccine world thinks that they won some landmark lawsuit.

Reagan didn’t do much for vaccines, but it isn’t fair to pin this one on him.

It seems that some folks think that the Department of Health and Human Services hasn’t been complying with federal vaccine safety mandates for 30 years.

The 1986 National Childhood Vaccine Injury Act includes a mandate for safer vaccines. — The National Childhood Vaccine Injury Act of 1986 includes a mandate for safer vaccines.

Really?

Which ones?

Did the US Government Lose a Landmark Vaccine Lawsuit?

While anti-vaccine folks are pushing this lawsuit victory (?) to make folks think that HHS has done absolutely nothing to promote vaccine safety in the last 30 years, that is obviously nonsense.

The lawsuit was actually just about the reporting requirements of paragraph (c) of section 2127 of the National Childhood Vaccine Injury Act of 1986.

It should be clear that the HHS has done plenty to promote vaccine safety though.

HHS Secretary Donna Shalala reported to the Senate Committee on Health Education Labor and Pensions in 1998. — HHS Secretary Donna Shalala actually reported to the Senate Committee on Health Education Labor and Pensions in 1998.

Even if no formal reports were filed, the HHS secretary did report to and appear before Congress. Come to think of it, they even sent some reports to Congress.

The Health Resources and Services Administration (HRSA), an agency of the U.S. Department of Health and Human Services, has commissioned almost a dozen reports about vaccine safety over the years.

And the Health and Medicine Division (HMD) division (previously known as the Institute of Medicine (IOM) of the National Academies of Sciences, Engineering, and Medicine has published a number of vaccine safety reviews and reports under commission of HRSA, an agency of HHS.

Where do folks think that all of those IOM vaccine safety reports and reviews come from? Were they sent to Congress?

The Assistant Secretary for Health leads development of HHS-wide public health policy recommendations, oversees 11 core public health offices — including the Office of the Surgeon General and the U.S. Public Health Service Commissioned Corps, which has approximately 6,500 uniformed health officers who serve in nearly 600 locations around the world to promote, protect and advance the health and safety of our nation and our world. He also oversees three Presidential and 11 Secretarial advisory committees. — The Assistant Secretary for Health leads development of HHS-wide public health policy recommendations, oversees 11 core public health offices and three Presidential and 11 Secretarial advisory committees. We have had a National Vaccine Plan since 1994.

And also consider that:

the National Vaccine Advisory Committee (NVAC), established in 1987, has had regular meetings and published regular reports about vaccine safety
a number of other vaccine safety oversight advisory committees and government groups were established, including the Advisory Commission on Childhood Vaccines, the Advisory Committee on Immunization Practices (ACIP), the Microbiology and Infectious Diseases Review Advisory Committee (MIDRAC) of NIAID, and the Vaccines and Related Biological Products Advisory Committee, with the Vaccine Interagency Group of the National Vaccine Program Office providing overall coordination. They all report to the Secretary of HHS.
the Vaccine Adverse Events Reporting System (VAERS) and Vaccine Safety Datalink were established in 1990, but it is important to keep in mind that VAERS was created from a merger of the CDC Monitoring System for Adverse Events Following Immunization (MSAEFI) and the vaccine reports contained in the FDA Spontaneous Reporting System (SRS) programs. It’s not like we just start following adverse events following immunization in 1990.
a Task Force on Safer Childhood Vaccines was established and completed a report, “identifying key issues and enhancing collaboration on behalf of vaccine safety” in 1996. Did someone forget to send it to Congress?
the Salk inactivated polio vaccine (IPV) replaced the oral polio vaccine (OPV) in 1996 because of a small risk of vaccine-associated paralytic poliomyelitis (VAPP), beginning with a sequential IPV-OPV vaccine schedule and then going to an all IPV schedule in 2000
the DTaP vaccine, which is supposed to have fewer side effects than DTP is licensed, and replaces DTP for all required doses by 1997, although DTP is never actually shown to have caused seizures or brain damage
RotaShield, the first rotavirus vaccine is licensed in 1998 but is soon withdrawn from the market in 1999 after it is associated with an increased risk of intussusception, a form of bowel obstruction
the Clinical Immunization Safety Assessment (CISA) Project was established in 2001
a new National Vaccine Plan was established in 2010, with the goal to develop new and improved vaccines, enhance the vaccine safety system, support communications to enhance informed vaccine decision-making, ensure a stable supply of, access to, & better use of recommended vaccines in the U.S., and increase global prevention of death & disease through safe & effective vaccination. Was the plan sent to Congress?
vaccine recalls have occasionally been issued
a White Paper on the U.S. Vaccine Safety System was published in 2011
a report on Safety of Vaccines Used for Routine Immunization
in the United States was published in 2014
a report on Overcoming Barriers and Identifying Opportunities for Developing Maternal Immunizations was published in 2016

Most importantly, new vaccines have been approved that protect our kids against many more now vaccine-preventable diseases.

HHS Settles Lawsuit Over Vaccine Safety Reporting

But wait, did the HHS even lose the lawsuit?

Not saying I'm surprised, but even Dr. Bob has bought into the idea that this lawsuit against HHS means something big. — Not saying I’m surprised, but even Dr. Bob has bought into the idea that this lawsuit against HHS means something big.

They actually didn’t.

They did settle a lawsuit though, a lawsuit which was then dismissed.

So like the CDC whistleblower movie that didn’t include a whistleblower, anti-vaccine folks think that they have a smoking gun about vaccine safety reports, except that it is very obvious that all kinds of reports about vaccine safety have been done over the years.

Vaccines are still safe. And they are still necessary.

What to Know About the HHS Vaccine Lawsuit

Although it does seem like HHS didn’t file the required formal reports and keep to the strict letter of the National Childhood Vaccine Injury Act of 1986, there is abundant evidence that they have actually done all of the work required to make sure that our vaccines are safe.

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).

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

VAXOPEDIA

Why Are the DPT and OPV Vaccines Still Used in Some Countries?

Why Are the DPT and OPV Vaccines Still Used in Some Countries?

More on the Continued Use of DPT and OPV Vaccines