Parents of unvaccinated children in London are to be contacted by the NHS in a bid to try and contain a polio outbreak in the UK.
Health chiefs declared a national incident on Wednesday following the return of the disease for the first time in nearly 40 years.
The virus was detected at the Beckton sewage treatment works, which covers a population of four million in north and east London. Signs of it were first found in February.
Now an investigation is searching for the source of the outbreak, so the area can be targeted with a vaccination drive. Anyone found to be infected might be asked to isolate.
The UK Health Security Agency believes a traveller, possibly from Pakistan, Afghanistan or Nigeria, shed the virus in their faeces after being given a live oral polio vaccine during an outbreak.
It is likely they then infected relatives by failing to wash their hands properly and contaminating food and drink. Officials are looking at the possibility that just one family – or an extended family – may be affected.
However, the NHS is starting up a major drive to ensure routine vaccinations are being taken up after the Covid-19 pandemic caused a lull in appointments.
Jane Clegg, chief nurse for the NHS in London, said: ‘The NHS will begin reaching out to parents of children aged under five in London who are not up to date with their polio vaccinations to invite them to get protected.’
But he told BBC Radio 4’s PM programme: ‘As a precaution, sensibly what the NHS will be doing in London is contacting those families that have children age five or below and just making sure they’re up to date with their polio vaccination status.’
Great Britain was pronounced clear of polio in 2003 with the last case coming in 1984, but experts repeatedly found samples of it in the waste water site in London this week.
Doctors, most of whom will have no direct experience of the disease, were yesterday given reminders of the symptoms and ordered to remain alert. In the worst cases polio can paralyse or even kill.
Most people show no signs of infection at all but about one in 20 people have minor symptoms such as fever, muscle weakness, headache, nausea and vomiting.
Around one in 50 patients develop severe muscle pain and stiffness in the neck and back. Less than one per cent of polio cases result in paralysis and one in 10 of those result in death.
Unvaccinated adults and parents of children who are behind with their polio jabs are urged to contact a GP, and youngsters should have had five doses between the ages of eight weeks and 14 years.
The live oral polio vaccine has not been used in the UK since 2004 but it is still deployed in some countries, particularly to respond to polio outbreaks. This vaccine generates gut immunity and for several weeks after vaccination people can shed the vaccine virus in their faeces.
These viruses can spread in under-protected communities and mutate into a ‘vaccine-derived poliovirus’ during this process. This behaves more like naturally occurring ‘wild’ polio and may lead to paralysis in unvaccinated individuals, as has happened abroad.
The UK uses an inactivated polio vaccine, which is given as part of a combined jab to babies, toddlers and teenagers as part of the NHS routine childhood vaccination schedule.
Vaccine-derived poliovirus type 2 (VDPV2), the one that has been detected in London, is the most common type. There were nearly 1,000 cases of VDPV2 globally in 2020.
Since 2019 every country in the world has been using vaccines that contain inactivated versions of the virus that cannot cause infection or illness.
But the UKHSA said countries where the virus is still endemic continue to use the live oral polio vaccine (OPV) in response to flare-ups.