British health authorities have advised that one-nine-year-olds throughout London receive a polio vaccine booster, after detection of the poliovirus in sewage from eight London boroughs, the U.K. Health Security Agency (UKHSA) said on Wednesday. The overall risk, nationally, of paralytic polio was low, the UKHSA added, because most people are protected by vaccination.
After type 2 poliovirus (PV2) was found in the Beckton (London) sewage treatment plant in February, further sampling was done upstream between February and July , and found at least one sewage sample with the virus in each of eight London boroughs. There was “ high genetic diversity” among the PV2 isolates, as per UKHSA, indicating that the transmission may have gone beyond a close group of persons.
The U.K. was declared polio-free in 2003, with the last known case of polio in the U.K. in 1984. Polio has been eradicated from most countries in the world, with India achieving that milestone in 2014, as per the World Health Organisation (WHO). The disease is still considered endemic in Pakistan and Afghanistan.
Of the 116 PV2 isolates that were identified in London, most were vaccine-like viruses, i.e., from individuals who have been vaccinated with an oral polio vaccine that contains a weakened polio virus, which is used in some countries. The U.K. stopped using the oral vaccine and moved to the inactivated polio vaccine in 2004.
Just a few of the isolates examined had sufficient mutations to be classified as ‘vaccine derived poliovirus’ (VDPV2). It is these few that are of “greater concern”, UKHSA said, because they behave more like the wild type (i.e., the naturally occurring virus), and could, as a rare occurrence, cause paralysis in non-vaccinated individuals.
“No cases of polio have been reported and for the majority of the population, who are fully vaccinated, the risk is low,” UKHSA Consultant Epidemiologist Vanessa Saliba said.
“But we know the areas in London where the poliovirus is being transmitted have some of the lowest vaccination rates. This is why the virus is spreading in these communities and puts those residents not fully vaccinated at greater risk,” she added.
UKHSA said it was working with governments in the U.S. and Israel where similar cases had been detected. Last month, a case of the virus was reported in the New York State in the U.S., in an unvaccinated man, the first of its kind in almost a decade. Health authorities in the State had urged people to ensure they are fully vaccinated.
