In recent days, headlines crying “more polio cases now caused by vaccine than by wild virus” are circulating online. But before you jump to conclusions about the safety of polio vaccines, you should look a little closer.
No, people are not catching polio from getting a polio vaccine. But there is some truth to those headlines. Here’s what’s really happening…
When and where did the initiative to eradicate polio begin?
There is still no known cure for polio, so efforts to save lives are focused on preventing its spread in the first place.
Global initiatives to prevent the spread of wild poliovirus began in 1988. Many, many countries haven’t had a reported case of polio in decades (you can see a full list of the last recorded polio cases here!)
According to the World Health Organization, “Polio does still exist, although polio cases have decreased by over 99% since 1988, from an estimated more than 350 000 cases to 22 reported cases in 2017. This reduction is the result of the global effort to eradicate the disease. Today, only 3 countries in the world have never stopped transmission of polio (Pakistan, Afghanistan, and Nigeria).”
Oral vs. Injected Polio Vaccine
Typically, Western countries including Canada and the United States now use injections of inactivated poliovirus to vaccinate the population. Unfortunately, this version of the vaccine can be too expensive to administer in other regions, so WHO and partners also rely on a cheaper option: oral polio vaccines.
Other benefits of the oral polio vaccine include the fact that it’s not necessary to have a nurse or physician administer it or to have readily available stock of sterile syringes.
Is the oral polio vaccine linked to real cases of polio?
The oral polio vaccine contains a weakened poliovirus that triggers the body to build immunity while it is making its way through the digestive tract. The virus is excreted after a short period of time, leaving the person to whom it was administered immune to polio.
In regions with inadequate sanitation systems, sometimes the weakened poliovirus can survive after being excreted and start to be circulated. The longer the virus is able to survive and reproduce, the more likely it could evolve into a dangerous version of polio.
This is known as a circulating vaccine-derived poliovirus (cVDPV), and it is not the same thing as wild poliovirus.
While cVDPV cases are possible, they are very rare. “Since 2000, more than 10 billion doses of OPV have been administered to nearly 3 billion children worldwide. As a result, more than 13 million cases of polio have been prevented, and the disease has been reduced by more than 99%. During that time, 24 cVDPV outbreaks occurred in 21 countries, resulting in fewer than 760 VDPV cases, ” the WHO reports.
How many cases of vaccine-derived polio have been reported to date?
According to WHO, there have been 176 vaccine-derived polio cases across the globe to date (as of November 2019).
These cases have been located in Angola, Benin, Central African Republic, Democratic Republic of Congo, Ethiopia, Ghana, Myanmar, Niger, Nigeria, Pakistan, Philippines, Somalia, Togo, and Zambia.
Should you be worried about the polio vaccine?
No, and here’s why.
First, Western countries are administered the injectable, inactive version of the polio vaccine, which is impossible to spread like cVDPV.
Second, cVDPV affects unvaccinated people who are exposed to the weakened polio vaccine that is excreted by people given the oral vaccine.
Third, cVDPV is exceptionally rare. The risks of getting wild poliovirus or exposing someone else to it are far, far greater than the risk of getting cVDPV. In fact, the Independent Monitoring Board cites suspicion of the polio vaccine as a major roadblock to the full eradication of polio across the globe.
The Independent Monitoring Board is a group set up by WHO to assess polio eradication all over the world. In their 2019 report, they identified a number of challenges standing in the way of progress against polio. These include:
- “Widespread hostility to, and rejection of, the oral polio vaccine in many deprived communities
- A weak emergency culture not commensurate with the present stage of
- A weak emergency culture not commensurate with the present stage of the eradication process
- Oppressive top-down demands stifling the eradication process Oppressive top-down demands stifling of the eradication process
- Oppressive top-down demands stifling local creativity and ingenuity and creating a climate of fear at the frontline
- The top-performing staff not being identified or sent to the most difficult places
- Action to raise essential immunization levels unconvincing and inadequate
- A program inundated with excessive amounts of data and weak in using insights to improve quality
- Levels of missed children in Afghanistan very high and rising fast
- Widespread environmental samples and community mistrust in the Pakistan Programme were not being given proper attention
- Wild poliovirus circulation in Nigeria could not be ruled out until the security situation improves and surveillance is conducted in inaccessible areas.”
The Global Polio Eradication Initiative (GPEI) plans to phase out the oral polio vaccine once the wild poliovirus has become completely extinct. At that point, only the inactivated polio vaccine would be used to ensure all populations are still immune to polio.
Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.
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