MIL-OSI United Kingdom: expert reaction to report from the UKHSA of poliovirus detected in sewage from North and East London


Source: United Kingdom – Executive Government & Departments

The UK Health Security Agency (UKHSA) have announced that an investigation is underway following poliovirus detection in sewage from North and East London.

Dr Kathleen O’Reilly, Associate Professor in Statistics for Infectious Disease and expert in Polio Eradication, said:

“In these investigations, ‘vaccine-derived’ poliovirus has been detected from several sewage samples from the north London area. These findings suggest that there may be localised spread of poliovirus, most likely within individuals that are not up to date with polio immunisations. The most effective way to prevent further spread is to check vaccination histories, especially of young children, to check that polio vaccination is included. The UK vaccinates against polio using the ‘inactivated’ vaccine (called the IPV) where there is no risk of onward spread. For families that have recently moved to the UK, I recommend that they contact their local doctors (“GP”) and they will provide further support to confirm that children are up to date with their vaccines. It is free to register.

“The findings are from sewage sampling, as people infected with poliovirus shed virus in their faeces, which can then be detected in sewage treatment plants. Sewage surveillance for polio, and other pathogens, have been extremely useful to detect emergence of pathogens and respond to these detections early, preventing disease and onward spread. The surveillance in London that identified vaccine-derived poliovirus is such an example. Another example is from Israel in 2014 where poliovirus was also detected in sewage samples, and polio cases were prevented through vaccination.

“Vaccine-derived poliovirus is present in many countries across the world, especially within the African continent and some countries in Asia. The origin of the vaccine-derived poliovirus is from certain versions of the live oral polio vaccine, which are used in a small number of countries. The UK has not used this vaccine for some years. Until all poliovirus are stopped globally, all countries are at risk, highlighting the need for polio eradication, and continued global support for such an endeavour.”

Prof Nicholas Grassly, Professor of Vaccine Epidemiology, Imperial College London, said:

What is vaccine-like and vaccine-derived poliovirus?  How/why can people who have had the oral polio vaccine shed virus; is the virus they shed normally a risk to other people?

“Oral polio vaccine contains a weakened, live virus that immunises us by growing in the intestine for a short period during which it can be detected in stool.  This virus can occasionally be transmitted and very rarely it can spread further to cause an outbreak of vaccine-derived poliovirus.  Whilst rare, these vaccine-derived polioviruses have lost their attenuating mutations and and are just as likely as the wild-type strain to cause paralysis.

Which polio vaccine do we currently use in the UK?  Why do some other countries still use (live) oral polio vaccine?

“Oral polio vaccine is easy to administer and gives good gut immunity that protects against infection and poliovirus shedding in stool if exposed.  It is needed to stop polio outbreaks in countries with poor sanitation where food and water may be contaminated with human waste.  In the UK the oral vaccine was replaced with an injectable inactivated polio vaccine in 2004.

Is it unusual to detect these viruses in sewage sampling?  What makes this situation different from previous situations?

“Polio persists in some of the poorest parts of the world and the UK quite frequently detects imported virus in sewage samples.  In this case, genetically related viruses have been detected since February in sewage from north and east London suggesting there may be local circulation.  Fortunately, so far no one has developed symptoms of the disease, which only affects about 1 in 200 of those infected, but it is important that children are fully up-to-date with their polio vaccines.  Until polio is eradicated globally we will continue to face this infectious disease threat.”

Dr David Elliman, consultant paediatrician at Great Ormond Street Hospital, said:

“Parents sometimes ask why, when diseases are uncommon in UK, or in the case of polio has been eliminated, do we continue to vaccinate against them.  The answer is that, although we are an island, we are not isolated from the rest of the world, which means diseases could be brought in from abroad.  The finding of vaccine derived polio virus in sewage proves the point.  Although the uptake of polio vaccines is high in UK, there are children who are unimmunised and therefore at risk of developing polio if in contact with this virus.  The risk is small, but it is easily preventable by the vaccine, which in the UK is killed and so cannot cause the disease.  There is no upper age limit for the vaccine.  Anyone who is not fully vaccinated against polio should seek advice from their health visitor or general practice.”

Prof David Heymann, Professor of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, said:

“Vaccine derived polio virus is now present in many countries around the world.  The virus results from a mutation of the Sabin virus that is a live virus used to vaccinate against polio, and it causes paralysis in some, though the majority of infections are asymptomatic.

“Sabin-virus based vaccine (live oral polio vaccine) is now only being used in countries that are in the active eradication phase of polio eradication – other countries have switched to inactivated polio virus vaccine that cannot mutate.

“The fact that it has been found in sewage in the UK attests to the strength of the surveillance programmes of UKHSA.  Its presence in the reminds us that polio eradication has not yet been completed in the world.  The high vaccination coverage using inactivated polio vaccine in the UK will limit the spread of vaccine derived polio and protect those who have been vaccinated against polio paralysis.”

Declared interests

Dr David Elliman: “I have no conflicts of interest.”

Prof David Heymann: “None.”

For all other experts, no reply to our request for DOIs was received.

MIL OSI United Kingdom