June 22, 2022
Wastewater surveillance has detected “several” closely related vaccine-derived polioviruses in London sewage, suggesting there has been some person-to-person spread, health officials said.
Outbreaks of vaccine-derived poliovirus occur when a live but weakened strain of virus included in vaccines spreads between people. The United Kingdom has not recorded a case of wild polio since 1984.
According to the U.K. Heath Security Agency (UKHSA), it is normal for routine surveillance to detect a few polioviruses every year in U.K. sewage, “but these have always been one-off findings that were not detected again.” In those cases, the viruses likely came from people who received an oral polio vaccine overseas and shed traces of the virus in their feces.
What is different about the viruses detected in London wastewater between February and May is that they are closely related, the UKHSA said, suggesting they have a common origin.
The viruses are vaccine-derived poliovirus type 2 (VDPV2), a strain of the virus that has been eradicated in the wild and has not been included in oral polio vaccines since 2016 but remains the most common cause of recent vaccine-derived poliovirus outbreaks, according to WHO.
There have been fewer than 800 reported cases of vaccine-derived polio globally in the last 10 years, according to the Global Polio Eradication Initiative (GPEI).
“The detection of a VDPV2 suggests it is likely there has been some spread between closely linked individuals in North and East London and that they are now shedding the type 2 poliovirus strain in their feces,” the UKHSA said. “The virus has only been detected in sewage samples and no associated cases of paralysis have been reported — but investigations will aim to establish if any community transmission is occurring.”
Vaccine-derived poliovirus can cause paralysis that is clinically identical to paralysis caused by wild polio, according to the CDC.
The U.K. has historically had a high level of polio vaccine coverage, but the UKHSA warned that national coverage for routine pediatric vaccines has declined, “and especially in parts of London over the past few years, so UKHSA is urging people to check they are up to date with their vaccines.” According to the GPEI, data suggest that polio vaccine coverage in London is 86.6%.
Vanessa Saliba, MD, MSc, a consulting epidemiologist for the UKHSA, said the risk for the public ls “extremely low” but warned undervaccinated communities may be at risk.
“Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower,” Saliba said in a statement. “On rare occasions it can cause paralysis in people who are not fully vaccinated so if you or your child are not up to date with your polio vaccinations it’s important you contact your [general practitioner] to catch up or if unsure check your Red Book.”
Jane Clegg, RN, MSc, the National Health Service’s chief nurse in London, said the NHS will be contacting parents of children who are not up to date on their polio vaccines.
CDC. Vaccine-derived poliovirus. https://www.cdc.gov/vaccines/vpd/polio/hcp/vaccine-derived-poliovirus-faq.html. Accessed June 22, 2022.
GPEI. Vaccine-derived poliovirus type 2 (VDPV2) detected in environmental samples in London, UK. https://polioeradication.org/news-post/vaccine-derived-poliovirus-type-2-vdpv2-detected-in-environmental-samples-in-london-uk/. Published June 22, 2022. Accessed June 22, 2022.
U.K. Health Security Agency. Poliovirus detected in sewage from North and East London. https://www.gov.uk/government/news/poliovirus-detected-in-sewage-from-north-and-east-london. Published June 22, 2022. Accessed June 22, 2022.
WHO. Staying polio free. https://www.who.int/southeastasia/activities/maintaining-polio-free-status/staying-polio–free. Accessed June 22, 2022.