Officials in London have announced launching a polio vaccine booster campaign for all children aged one to nine after the virus was detected in sewage.

The virus, which can cause paralysis, has been found 116 times in London’s wastewater since February. The UK Joint Committee on Vaccination and Immunisation said a targeted inactivated polio vaccine booster dose should be offered to all children in all London boroughs.

“This will ensure a high level of protection from paralysis and help reduce further spread of the virus,” the UK Health Security Agency (UKHSA) said in a statement announcing the move.

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The urgent immunisation campaign will see nearly a million children getting the precautionary dose. 

According to the UKHSA, most of the samples contained vaccine-like virus, but some showed “sufficient mutations to be classified as vaccine derived poliovirus.” This was more concerning as such virus behaves more similarly to “wild polio and may, on rare occasions, lead to cases of paralysis in unvaccinated individuals.”

Dr Vanessa Saliba, a consultant epidemiologist at UKHSA, said, according to BBC: “All children aged one to nine years in London need to have a dose of polio vaccine now – whether it’s an extra booster dose or just to catch up with their routine vaccinations.”

“No cases of polio have been reported and for the majority of the population, who are fully vaccinated, the risk is low. But we know the areas in London where the poliovirus is being transmitted have some of the lowest vaccination rates,” Saliba said.

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The majority of people with the infection have no symptoms but some feel flu-like symptoms with high temperature, sore throat, headache, stomach pain and muscle ache.

The last case of polio in the UK was in 1984, according to the UKHSA statement.

“Decades ago before we introduced the polio vaccination programme around 8,000 people would develop paralysis every year,” Saliba added.