The NHS is offering children aged 1 to 9 in London a polio vaccine. This will either be a booster on top of your child’s routine immunisations or a catch up dose.
The NHS will contact you to book an appointment. https://www.nhs.uk/conditions/polio/
The best source of information is the polio booster page: https://www.gov.uk/government/publications/polio-booster-campaign-resources/have-your-polio-vaccine-now-information-for-parents
And the polio vaccine leaflet for parents: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1097153/UKHSA_12440_polio_leaflet_for_parents_and_carers.pdf