Polio can be eradicated and there are effective vaccines against it.

Afghanistan and Pakistan are the only two countries where wild polio is still endemic, and are targeted by eradication programmes to stop the virus spreading to other countries.

In the UK, the injected polio vaccine is used.

It contains inactivated virus (IPV) and is safe and effective in protecting the immunised person from paralysis, but it is less effective at inducing local immunity in the gut, so vaccinated people can still become infected and shed infectious virus, even though they may not show symptoms themselves.

The oral polio vaccine (OPV), which contains live but weakened virus, is ideal for this purpose.

This vaccine can induce potent gut immunity and it can prevent the shedding of wild polioviruses.

The downside of using OPV is that the weakened virus can mutate, and in rare cases, it can revert to paralysis-causing variants.

Indeed, the virus detected in London sewage was of the vaccine-derived variety, VDPV type 2.

There is still no wild poliovirus in the UK.

IPV is safe, free and effective to prevent polio disease.