A British man who was fully vaccinated against polio has been shedding the virus for nearly 30 years. He was vaccinated with the live weakened poliovirus vaccine, but due to an immune disorder, the poliovirus survived in his system. He shed the virus for all of these years in his stool. While many might think that that's not a real public health problem, because it was a weakened virus, researchers say it is actually a major concern.
The weakened polio virus mutated over the years, because viruses naturally mutate. The man's common variable immunodeficiency (CVID) allowed it to survive in his body. While in his body, the virus changed from the weakened virus that was in the polio vaccines he was given into a form of polio that can actually cause paralysis. Shockingly, all these years, he had no idea that he was shedding polio.
A team from the National Institute for Biological Standards and Control in Potters Bar, Hertfordshire, discovered the situation and now fear that similar cases are out there. Any one of them, the researchers claim, could trigger an outbreak. Their findings were published in the journal PLOS Pathogens, which included a look at two other immunodeficient patients in the U.K. from whom the researchers were also able to isolate vaccine derived poliovirus strains.
"While maintaining high immunisation coverage will likely confer protection against paralytic disease caused by these viruses, significant changes in immunisation strategies might be required to effectively stop their occurrence and potential widespread transmission."The British man was given his polio vaccines at five-months-old, seven-months-old, and 12-months-old. He was given an additional booster when he was around seven-years-old. Later, doctors diagnosed him with an immune disorder that made it so that the weakened poliovirus he was given in the form of a vaccine was not able to be fought off by his immune system. It stayed and thrived in his own gut. His feces tested positive for high levels of mutated poliovirus. The researchers believe he has been shedding variants of poliovirus for 28 years. His infection was eventually killed using blood plasma from people with healthy immune systems, according to the article the research team published.
"In conclusion, we describe a patient who has been excreting highly virulent and antigenically modified type 2 poliovirus at high titres for a period estimated to be twenty eight years so far. This is by far the longest reported poliovirus excretion and represents the most comprehensive collection of iVDPV (vaccine-derived polio viruses from immunodeficient individuals) sequential isolates available."The team also discovered highly-mutated strains of polio which they said came from the vaccines themselves in sewage samples in Slovakia, Finland, Estonia, and Israel. The BBC reported on the sewage samples on Friday.
"All bore the molecular fingerprints of "iVDPVs" - vaccine-derived polio viruses from immunodeficient individuals.The live attenuated polio vaccine (OPV) is still in use today in many parts of the world, but was discontinued in the United States in 2000, according to the CDC. At that time, the U.S. began using the inactivated poliovirus vaccine (IPV). According to the authors of the PLOS article, most type 2 poliomyelitis cases in India in the last decade, for example, were due to "vaccine-related poliovirus strains in either recipients, their immediate contacts or after the vaccine virus has regained the ability to transmit and circulate freely." Switching to an inactivated vaccine, the authors stated, could prevent all of the vaccine-associated paralytic poliomyelitis cases, which occur only in "a very small proportion of vaccines" of the live weakened polio vaccines.
"The researchers are calling for enhanced surveillance including sewage sampling and stool surveys to search for the presence of iVDPV strains.
"They also suggest the development of efficient anti-viral treatments to interrupt virus replication in people who [have] deficiencies in their immune system."
In the U.K., the government made the switch to the inactivated polio vaccine in 2004, so some immunodeficient people as young as 12 and 13-years-old in the U.K. could still be shedding live poliovirus without anyone even knowing.