Tag: IPV

What Is the Morbidity/Mortality Rate of the Polio Vaccine vs the Wild Virus?

Some anti-vaccine folks still think that the risks of vaccines are far greater than the risks of the vaccine-preventable diseases they keep you from getting.

As more people are vaccinated and diseases disappear, they forget how bad those diseases are, skip or delay getting their vaccines, and trigger outbreaks.
As more people are vaccinated and diseases disappear, they forget how bad those diseases are, skip or delay getting their vaccines, and trigger outbreaks. Photo by WHO

They aren’t, but you can kind of understand why they might think that with a disease like polio, when they might never actually have known anyone to have the disease.

What Is the Morbidity/Mortality Rate of the Polio Vaccine vs the Wild Virus?

Still, even though polio is under good control and close to being eradicated, the risk/benefit ratio clearly favors getting vaccinated and protected.

That’s because the polio vaccines are very safe and if we stopped vaccinating, polio could come back.

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.”

OPV Cessation

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)!

Of course, the issue with the OPV vaccines is that they rarely cause vaccine-associated paralytic polio (VAPP) and circulating vaccine-derived polioviruses (cVDPV).

Fortunately, this is even less common with bOPV.

As this chart from the WHO shows, polio vaccines are very safe.
As this chart from the WHO shows, polio vaccines are very safe.

So morbidity (getting sick)/mortality (dying) from polio vaccines is low.

There were only 31 cases of wild polio in 2018, in Afghanistan and Pakistan, and an additional 102 cases of cVDPV in 7 countries.

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

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.
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.

More on the Continued Use of DPT and OPV Vaccines