- Traces of poliovirus have been detected in routine sewage surveillance in the United Kingdom. Health officials say the virus identified is vaccine-derived.
- The risk to the public is low since most people in the U.K. will be protected through prior vaccination through polio; those under 5 will likely soon be vaccinated.
- In the U.S., at least 92 percent of children are vaccinated against polio.
Health officials in the United Kingdom have identified traces of poliovirus during routine sewage screening.
Typically, routine sewage surveillance detects poliovirus a couple of times a year, but between February and May, health officials detected several sewage samples with poliovirus.
The virus has since evolved and is now classified as a ‘vaccine-derived’ poliovirus type 2 (VDPV2).
Health authorities say there have been no serious cases of illness but suspect there has been community transmission among kids in North and East London.
Health authorities say that most of the U.K. population will be protected against poliovirus through vaccinations they receive in childhood.
Children under 5 who live near London will soon be invited to get vaccinated against polio, according to health officials.
“VDPV2, or type 2 poliovirus, is a type of poliovirus derived from an oral polio vaccine which utilizes a live form of the virus. For a short period of time, a newly vaccinated individual may potentially transmit the live virus through stool,” Hannah Newman, MPH, CIC, FAPIC, the director of infection prevention at Lenox Hill Hospital, told Healthline.
What is vaccine-derived poliovirus?
There are two types of vaccines available for polio — inactivated polio vaccine (IPV) and oral polio vaccine (OPV).
IPV is used in the United States and the U.K. It does not contain functional virus.
OPV, on the other hand, is a live attenuated vaccine. It is an extremely effective vaccine, but it contains the risk of circulating vaccine-derived poliovirus (cVDPV).
“The live oral polio vaccine (OPV) was recommended in the United States from 1963-2000; and switched to the current recommendation to utilize inactivated poliovirus vaccine (IPV) at that time. OPV is still administered in some countries,” Newman said.
Some people recently vaccinated with OPV can shed infectious virus in their stools. This can be detected in wastewater surveillance.
How cVDPV can spread
“The vaccine is designed to mimic natural polio virus which is shed via the fecal route,” Dr. Amesh Adalja, an infectious diseases expert and senior scholar at the Johns Hopkins University Center for Health Security, told Healthline.
According to Adalja, this is one of the touted benefits of the OPV — the fecal shedding can ultimately immunize people who are not vaccinated and help protect communities.
There isn’t a risk of the virus spreading through wastewater systems, according to Newman. Still, transmission can occur if an unvaccinated person is exposed to the stool or respiratory droplets of person with polio.
In areas with low vaccination rates it is possible that the virus can spread from one child to another, and over months to a year it can mutate and cause paralysis similar to the wild poliovirus. This mutated version of the virus can spread even more widely, leading to cVDPV.
In certain instances, it can cause paralysis. It can also recombine with related viruses and spread, according to Adalja.
“The current hypothesis is that [person with polio] may have brought the virus into London and spread to others who weren’t immunized,” Newman said.
The risk is low but vaccinations are advised
Newman says the risk to the general public is very low. Polio immunization is part of the routine vaccination schedule in the United States.
“CDC data shows 92.4% of U.S. children under 24 months are vaccinated against polio. This is great vaccine coverage, and I am confident that we would be protected against any potential threat,” Newman said.
Polio predominantly impacts children under 5, but it can people who are unvaccinated are also at risk for developing the disease, according to Newman.
People can request immunization from their physician or local health department.
That said, anyone who has not been vaccinated should make an appointment to get immunized against polio, Newman added.
“I would recommend vaccination to anyone who is not fully immunized based on current poliovirus vaccine recommendations,” Newman said.
The bottom line:
Traces of poliovirus have been detected in routine sewage surveillance in the United Kingdom. Health officials say the virus identified is vaccine-derived. There appears to be community transmission among children in the area, but the risk to the public is low. Most people in the U.K. will be protected through prior vaccination through polio; those under 5 will likely soon be vaccinated.