The UK Joint Committee on Vaccination and Immunization said all children aged 1 to 9 in all London boroughs should be offered a targeted booster shot of inactivated polio vaccine.
“This will ensure a high level of protection against paralysis and will help contain the further spread of the virus,” the UK Health Safety Authority (UKHSA) said in a statement announcing the move.
Around 1 million children of this age live in the London area, according to the latest data from the UK Office for National Statistics.
A total of 116 virus isolates were identified in 19 sewage samples collected in London between February and July, according to the UKHSA.
While most samples contained vaccine-like viruses, some “showed sufficient mutations to be classified as vaccine-derived poliovirus.” The UKHSA said this was more worrying as such a virus behaved more like ‘wild polio’ and in rare cases could lead to cases of paralysis in unvaccinated people.
The authorities emphasized that the vaccination campaign was a precautionary measure.
“No cases of polio have been reported and the risk is low for the majority of the population that is fully vaccinated. But we do know that areas of London where poliovirus is transmitted have some of the lowest vaccination rates,” said Dr. Vanessa Saliba, a consultant epidemiologist at UKHSA, said.
Vaccines are key as there is no cure for polio
Polio is caused by an enterovirus called poliovirus. It was one of the most feared diseases in the world until Dr. Jonas Salk invented the polio vaccine in 1954 and tested its safety.
By 1988, reported cases of polio worldwide peaked at 350,000, according to the World Health Organization.
About 1 in 4 infected people have flu-like symptoms such as a sore throat, fever, tiredness, nausea, headache and stomach ache. Up to 1 in 200 people will develop more serious symptoms, including tingling and numbness in the legs, brain or spinal cord infection, and paralysis, according to the US Centers for the Disease Control and Prevention.
There is no cure for polio. Treatment to manage symptoms may include medication to relax muscles, and heat and physical therapy to stimulate muscles. However, any paralysis caused by polio is permanent.
The last polio case in the UK was in 1984, according to the UKHSA statement.
“Decades ago, before we introduced the polio vaccination program, about 8,000 people developed paralysis each year,” Saliba added.
According to the Global Polio Eradication Initiative, a WHO program, there are three strains of the virus, two of which have been eradicated worldwide. A species of wild poliovirus is still circulating in Pakistan and Afghanistan. Transmission can also occur if an area does not have enough children vaccinated.
Last month, a person from Rockland County, New York was diagnosed with polio, the first case detected in the United States in almost a decade. The unvaccinated young adult developed weakness and paralysis, said the county’s health commissioner at the time, Dr. Patricia Schnabel Ruppert.
This story has been updated with additional information.
CNN’s Benjamin Brown, Molly Stazicker, Zahid Mahmood and Brenda Goodman contributed coverage.