British health authorities will offer children under 10 living in London an extra dose of polio vaccine amid growing concern about a return of the disease.
Although no one has tested positive for infection with the type of polio virus that can cause paralysis, authorities have nonetheless found it in several London sewage samples recently. This suggests “there is some level of transmission of the virus” in parts of London that “has passed a close network of a few individuals”, the UK Health Security Agency said in a statement.
The UK’s expert vaccine advisory committee has recommended offering the extra polio booster to children after reviewing polio vaccine coverage in London, which is falling behind the Organization’s targets global health.
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Of the 116 polio viruses isolated from London sewage samples in recent months, the vast majority are relatively harmless versions classified as “vaccine-like” viruses. People can spread this version through their faeces after receiving a live attenuated oral version of the polio vaccine which is no longer offered in the UK.
However, if this version of the virus mutates enough, it sometimes becomes a more dangerous strain that can cause paralysis on rare occasions. On several occasions in London since February, this more dangerous strain, known as the “vaccine-derived” polio virus, has been detected in sewage samples.
Normally, surveillance would pick up only pinpoint traces of the vaccine-like virus per year, and consistent detection in recent months warrants further intervention, health officials said.
The aim of the booster program is to boost protection against polio in London and slow transmission, officials said. Nationally, the overall risk of paralytic polio is considered low because most people are protected from it by vaccination, the UKHSA said. Meanwhile, authorities are also expanding sewage monitoring in London and the rest of the country to determine if the virus has spread elsewhere.
People can often transmit the polio virus without showing symptoms, although some suffer from a flu-like illness with fever, sore throat and headache. Often these symptoms go away without intervention, but in some cases the virus attacks nerves in the spine and base of the brain, which can lead to paralysis. The virus can be life-threatening if the respiratory muscles are affected.
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The last case of wild polio in the UK was in 1984 and the country was declared polio-free in 2003.
The United States reported its first case of polio in nearly a decade in July, in an unvaccinated 20-year-old man living in New York state. Another case was reported in March in Israel when an unvaccinated young girl developed paralysis and later tested positive for polio.
British health authorities said they were working with peers in the United States, Israel and the WHO to probe the links between what is being detected in London and cases reported in those two countries.
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