Children in London are being offered polio vaccine boosters after sewage samples with the virus were found in multiple areas across the city.
The U.K. Health Security Agency announced Wednesday that all children between ages 1 and 9 across the British capital will be eligible to receive an inactivated polio vaccine booster.
"This will ensure a high level of protection from paralysis and help reduce further spread of the virus," the agency said in a statement.
"While the majority of Londoners are protected from polio, the [National Health Service] will shortly be contacting parents of eligible children aged 1 to 9 years old to offer them a top-up dose to ensure they have maximum protection from the virus," Jane Clegg, chief nurse for the NHS in London, added.
There are more than 1 million children between those ages who live in London as of mid-2020, the latest year for which data is available, according to the U.K. Office of National Statistics.
Between February 8 and July 5 of this year, poliovirus has been detected in 19 sewage samples across nine boroughs including at Beckton Sewage Treatment Works in London, which is the largest sewage treatment plant in the U.K.
Recently, a report indicated a polio case in New York was genetically linked to the samples found in the U.K.
Polio vaccines are part of routine immunizations for children. In the U.S., vaccinated children are not recommended to get a booster shot at this time.
According to the UKHSA, the booster program will begin in the areas where the virus has been detected and where vaccination rates are lowest before being rolled out across the city.
"The NHS in London will contact parents when it's their child's turn to come forward for a booster or catch-up polio dose -- parents should take up the offer as soon as possible," the agency's statement read.
On July 21, health officials reported a case of polio was discovered in Rockland County in New York -- just north of New York City -- in a 20-year-old unvaccinated man.
The man contracted vaccine-derived polio, which means he was infected by someone who received the oral polio vaccine, which is no longer used in the U.S. or the U.K.
The oral vaccine uses a live weakened virus, which -- in rare cases -- can spread through fecal matter and infect unvaccinated individuals. Comparatively, the injectable polio vaccine, uses an inactivated virus.
As of Aug. 5, 11 samples were genetically linked to the Rockland County patient including six samples collected in June and July from Rockland County and five samples collected in July from nearby Orange County, health department data shows.
However, health officials have said the majority of the population is not at risk for polio because most were vaccinated as part of their regular childhood immunizations, but that it's important for those who are unvaccinated to get their shots.
The New York State Health Department told ABC News its focus would be on ensuring immunizations.
"Our current focus is to ensure unvaccinated New Yorkers and children get immunized against polio and that they are up to date with their polio immunization schedule," the department said.
The Centers for Disease Control and Prevention is the organization in the U.S. that makes vaccine recommendations, but has not suggested any such move to add a fifth dose of polio vaccine to the current vaccine schedule underway.
The CDC did not immediately respond to a request for comment from ABC News.
The agency recently told ABC News the U.S. health agency is deploying a team to New York to investigate the case in Rockland County. The team will also administer vaccines in the county.
"These efforts include ongoing testing of wastewater samples to monitor for poliovirus and deploying a small team to New York to assist on the ground with the investigation and vaccination efforts," the agency said in a statement.