LONDON — Every child in London ages 1 to 9 should be offered a booster shot of the polio vaccine, U.K. health authorities have said, as doctors warn that polio threatens to make a comeback.
The British Health Security Agency said Tuesday it had detected polio viruses from sewage water in eight of the U.K. capital’s 32 boroughs.
Although the agency has not found anyone infected with the virus, the news came as a shock in Britain, which was declared polio-free in 2003 and had its last confirmed case in 1984.
To prevent a potential outbreak, the government introduced a public health campaign this week that said booster shots should be offered to children ages 1 to 9.
The rate of vaccination for polio is lower in the capital than in the rest of the country. The World Health Organization target for polio vaccination is 95%. London is at 86.7%.
“What’s worrying is that it has been transmitting in the community,” Dr. Deepti Gurdasani, an epidemiologist at Queen Mary University of London, said Wednesday.
She said that “gives the virus opportunities to mutate.”
Gurdasani said it was “really concerning” that the Health Security Agency had “found cases of what it calls a vaccine-derived virus,” a virus that can be traced back to the oral polio vaccine. That vaccine relies on a live but weakened form of the virus to spur an immune response. The U.K. no longer uses that type of vaccine, but other countries do.
People who take the oral polio vaccine can briefly excrete the virus, and if a community has a low vaccination rate, the virus could spread.
If it circulates widely enough for long enough among unvaccinated people, it can mutate, and it “may develop properties of the original virus,” Gurdasani said.
She added that vaccination rates in Britain for polio and other viruses had been falling behind those of other developed countries and that if the virus is not suppressed, it could spread nationally. As in the U.S., all children in the U.K. are supposed to get vaccinated against polio. The new boosters will supplement that protection.
Gurdasani said it felt like there was “a level of complacency” in the U.K.
But Kathleen O’Reilly, a professor at the London School of Hygiene and Tropical Medicine, said there are likely to be many reasons the polio vaccination rate is lower in London.
Like many other large cities, she said, London “has a diverse and mobile population, which means that childhood vaccinations are sometimes challenging for parents to arrange.”
“For this reason, cities often have lower vaccination rates than other settings, and more resources are required to deliver vaccination,” she said.
Polio, or poliomyelitis, is a highly infectious viral disease that largely affects children under age 5 that is mainly spread through contact with human fecal matter. Symptoms include fever, fatigue, vomiting and muscle stiffness. Around 1 in 200 polio infections lead to paralysis.
Although polio has largely been eradicated from developed countries, the WHO says the virus is still endemic in places such as Pakistan, Afghanistan and Nigeria.
The British announcement comes less than a month after health officials in New York state reported the first case of polio in the U.S. in a decade.
The state health commissioner, Dr. Mary T. Bassett, warned last week that the case, discovered in Rockland County, north of New York City, may be the “tip of the iceberg.” She urged unvaccinated residents to get immunized against the virus, warning of the potential for “much greater” community spread.
Israel also ramped up its polio vaccination push for children ages 6 weeks to 6 years after a 4-year-old was infected in March.
If vaccination rates do not improve in the U.K., other viruses could also make comebacks, Gurdasani said.
“There’s definitely a trend in the U.K. to move away from good practices that were adopted a long time ago for a very good reason,” she said.