Polio: why is there a drive to vaccinate children in London?

As public health officials announce a polio vaccine booster programme for children in London, we take a look at the reasons for the campaign.

Who is being offered the polio vaccine?

All children aged one to nine in London are expected to be offered a polio vaccine in the next few weeks. For some, this will be part of a “catchup” programme to ensure they are up-to-date with their childhood vaccinations, while for others it will be a booster vaccination that is being offered to all children in London in this age group.

Parents and carers will be advised by their GP when it is their child’s turn to come forward for a vaccination.

What vaccine is being used?

The vaccine used in the UK is known as the inactivated polio vaccine (IPV) – meaning it cannot cause polio. This vaccine is very safe and effective.

IPV is typically given in combination with vaccines for other conditions, such as tetanus and diphtheria, although the combination used varies with age.

The Guardian understands all three types of IPV-containing jab used in the UK will be deployed in the polio vaccine booster programme to ensure rapid access to supply.

Related: All children aged one to nine in London to be offered polio vaccine booster

Why are the extra vaccines only being given in London?

At present, geographical analysis of sewage samples has revealed poliovirus in wastewater from across north-east and central London.

As a result, public health officials are focusing on boosting levels of vaccination in London, starting in boroughs where poliovirus has been detected and vaccination rates are low.

However officials say sewage surveillance for polio is being expanded in and beyond London to explore if poliovirus has spread outside the capital.

Why are young children the focus for vaccination?

One issue raised by the Joint Committee on Vaccination and Immunisation (JCVI) is the low uptake of polio vaccine-containing jabs among this demographic.

“Vaccination coverage for the three-dose primary schedule in one-year-olds in London is well below the average achieved for the UK and uptake of the preschool booster in five-year-olds is even lower,” the committee has said, adding that there is significant overlap between areas with low levels of vaccine coverage and those where poliovirus has been found in the wastewater.

What’s more, public health officials say young children may be less able to practise good hygiene – an important factor managing the spread of the poliovirus.

By vaccinating young children public health officials are hoping to both strengthen their protection against paralysis – a rare, but life-threatening symptom of polio – and curb the spread of the virus.

How worried should parents and carers be?

At present, the UK Health Security Agency says most of the poliovirus-containing samples from London sewage involve vaccine-like poliovirus – a weakened form of the virus that cannot cause polio. This virus can be shed in the faeces of people recently vaccinated with live oral poliovirus vaccine (OPV), which has not been used in the UK since 2004.

However if vaccine-like poliovirus circulates it can gain mutations that increase its virulence, resulting in vaccine-derived poliovirus which has the potential to cause paralysis in those who are unvaccinated. Some of the samples from the London sewage have been found to contain this type of poliovirus.

No cases of polio or related paralysis have yet been reported and the JCVI says paralysis from vaccine-derived polioviruses is rare. However the committee notes non-immune children are at risk.

“I recognise parents and guardians will be concerned about the detection of polio in London, however I want to reassure people that nobody has been diagnosed with the virus and the risk to the wider population is low,” said Steve Barclay, the health secretary.

As a result of vaccinations the last case of polio in the UK was in 1984.