"Vaccine-derived" cases of poliovirus are the result of low immunization rates, rather than an issue with the vaccine itself.
Following the recent announcement by the U.K. Health Security Agency that poliovirus has been found in sewage in North and East London, a number of posts on social media have framed this in a conspiratorial manner. These posts often create unnecessary fear and obfuscate the facts.
In one particular post, a Facebook user claims that this news raises a number of questions, including why the polio virus was detected if it was previously declared to have been eradicated; the efficacy of vaccines in general; and why the government is encouraging people to make sure that they are properly vaccinated. The post goes on to state that polio is “just another virus” akin to the common cold or flu.
The post contains a number of misconceptions and inaccurate information. First, the post confuses the terms "eliminated" and "eradicated" –– likely because these two terms are often used interchangeably by the media and general public.
A disease is considered eliminated within a specific region when it is no longer circulating through the population of that region. A disease is considered eradicated when it is no longer present in the global human population at all. The poliovirus is considered an eliminated virus in the U.K. as it is no longer in circulation among the general population. It is not considered eradicated because polio is still considered endemic in some countries, for example, Afghanistan and Pakistan.
The poliovirus is said to have been eliminated around much of the world because it used to be endemic around the world. Following the introduction of vaccination programs around the world throughout the 20th century, the number of new polio cases was successfully reduced to the point where it no longer posed a risk to the general public. The last documented case of “wild” polio in the U.K. occurred in 1984.
The post accurately claims that the overwhelming majority of new cases of polio around the world are “vaccine-derived.” The Global Polio Eradication Initiative explains how this occurs: “The oral polio vaccine that has brought the wild poliovirus to the brink of eradication has many benefits: the live attenuated (weakened) vaccine virus provides better immunity in the gut, which is where polio replicates. The vaccine virus is also excreted in the stool, and in communities with low-quality sanitation, this means that it can be spread from person to person and actually help protect the community. However, in communities with low immunization rates, as the virus is spread from one unvaccinated child to another over a long period of time (often over the course of about 12-18 months), it can mutate and take on a form that can cause paralysis just like the wild poliovirus. This mutated poliovirus can then spread in communities[.]”
This means that “vaccine-derived” cases of polio are not a fault with the vaccine itself, as the post implies, but a result of inconsistent vaccine uptake. This means that cases of vaccine-derived polio do not undermine the assertion that polio was successfully eliminated throughout much of the world, as polio no longer poses the endemic threat to public health and safety that it once did, thanks to the efforts of various education and vaccination programs around the world.
Furthermore, the post on Facebook questions why the U.K. government was testing for polio in the wastewater and implies that this ought to raise suspicion. The answer is simple: many of the viruses that are harmful to human health affect the gastrointestinal tract, so the U.K. routinely monitors sewage and wastewater content for a range of pathogens, such as poliovirus, norovirus, hepatitis A and E, adenovirus, and rotavirus. Because poliovirus is eliminated rather than eradicated, there remains a chance that visitors from regions where the virus is still in circulation could re-introduce it, which would affect populations with inconsistent vaccine uptake.
The post makes a potentially dangerous claim when it states that poliovirus is akin to the common cold or flu. This is false because while the flu can be dangerous to older generations or people with compromised immune systems, it is relatively rare that it is life-threatening. The poliovirus, on the other hand, primarily affects young children under the age of 5 –– and 1 in 200 poliovirus infections lead to irreversible paralysis. Among those paralyzed, 5 to 10 percent die as a result of their breathing muscles becoming immobilized.
The post contains a number of inaccuracies and some dangerous misinformation. We have therefore marked the post as false.