The targeted action in the UK capital is being undertaken on the advice of the independent Joint Committee on Vaccination and Immunisation (JCVI) to ensure a high level of protection from paralysis and help reduce further spread of the virus.
The virus found in London sewage is mainly the vaccine-like virus, which is found when children vaccinated with a particular kind of live vaccine - now only used overseas - shed the virus in their faeces. This harmless virus can transmit between unvaccinated children, and while doing so, can mutate back into a more dangerous version of the virus, and cause illness.
Pakistan is the only country after Afghanistan, with deposits of polio virus. In the past, militant groups have not only targeted and killed dozens of polio workers but have also threatened locals, especially in the tribal areas of Pakistan, of dire consequences of they let their children get polio vaccinations.
"It is important to realise that the polio virus still exists in our surroundings and no child is safe until all children are truly vaccinated," The Express Tribune quoted the top official as saying.
The UK Health Security Agency noted that the virus was probably imported from some country, and has asked parents to ensure their children were fully immunised against the crippling disease.
War-torn Ukraine is also grappling with an outbreak of vaccine-derived polio with two cases in the country's west last year, and the most recent in December. Poliovirus was also isolated from 19 healthy contacts, Nature reported.
The programme will cover 17 crore children aged under five years to maintain the country's 'polio-free' status.
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