The fight against polio is considered one of the great vaccination success stories: the infectious disease is close to being eradicated worldwide, and Europe, for example, has been officially polio-free since 1990. But now experts have found the virus in London’s sewage. This means that the pathogen has been detected in Great Britain for the first time in 40 years.
The impression that the dreaded polio is now breaking out again on a large scale is deceptive. It is not uncommon for polioviruses to keep popping up somewhere in the world – not in spite of the global eradication campaign, but because of it. It is also not the first such case in Europe.
The worldwide vaccination campaign, which has eradicated the wild polio virus in almost every country on earth, is based on a vaccine with reproducible polio viruses – the famous oral vaccination. This live vaccine contains weakened pathogens that can still reproduce and even infect other people. Those who have been vaccinated shed the virus for about two to six weeks.
Why you can get infected with the vaccine
There is another vaccine that contains inactivated viruses, but it has to be injected into the muscle. The oral intake of the live vaccine, on the other hand, offers considerable advantages if you want to vaccinate millions of children worldwide. And in fact it is even a positive side effect that the virus can still spread, because in this way vaccinated children also vaccinate part of their family. A phenomenon known as silent freedom.
In addition, only the oral vaccination reliably protects against infection. The inactivated vaccine prevents disease but not infection, so poliovirus can circulate silently if only this vaccine is used. Therefore, in the 1960s and 1970s, the live vaccine was used with preference to additionally suppress the wild poliovirus. Last but not least, the weakened vaccine virus is only slightly contagious and usually dies after just one or two infections.