NIBSC scientists have published new research that describes a man from the UK who has been chronically infected with a virus type present in the Sabin Oral Poliovirus Vaccine and has continued to excrete the virus for the last 28 years.
Live polio vaccine viruses can sometimes genetically change back to a form that can cause disease. This case shows that vaccination against polio needs to carry on for a long time to avoid the risk of reintroducing the disease.
Cases like this do pose a risk to polio eradication. But the virus neutralisation assays (tests) with human and animal sera, cited in the study, show that despite extensive changes in the vaccine-derived virus strains from this patient, the current polio vaccines give adequate protection against paralytic diseases caused by these viruses.
Researchers analysed more than 150 stool samples collected between 1995 and 2015 from a white male. The individual received a full course of childhood immunizations, including OPV at 5, 7, and 12 months, with a booster at about 7 years of age. He was later diagnosed with an immunodeficiency, which can affect the ability of the immune system to kill viruses in the digestive tract.
The global polio eradication initiative is the most ambitious and complex public health programme directed at a single disease in history with a projected cost of $16.5 billion. Polio serotypes are now restricted to parts of Pakistan and Afghanistan and there is a real probability of total eradication in the near future.
NIBSC scientists are working on several international collaborative projects to tackle outstanding issues relating to polio. These include:
The research was published in PLoS Pathogens in August 2015.