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

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