The finding of the poliovirus in several samples taken of the London sewer system during 2022 is not much of a concern for communities with such high vaccination rates against this virus as the UK, where children are immune to low odds of paralysis. However, it is the reminder of a potential individual catastrophe for families with unvaccinated or incompletely vaccinated children in the British capital, unless urgent action is taken.
In these times of pandemic, it should not be necessary to remind ourselves that there are various dangerous viruses out there, and always have been. But intervening urgently to control epidemics and outbreaks with vaccines is relatively new. The devastating polio epidemic in the 1940s and 1950s, which left thousands of paralyzed children in the UK, was in the public eye at the time, with familiar images of hospitals packed with children in coffin-shaped artificial lungs. or paralyzed and forced to wear orthopedic prostheses.
The epidemic eventually died out in many countries as a result of the massive use of two different types of polio vaccines, created by Jonas Stalk and Albert Sabin. The success of the polio program led to the creation in 1963 of the Joint Committee on Vaccination and Immunization (JCVI), and the development of a coordinated immunization program that protects our children to this day.
In the 1980s, despite the invention of the vaccine 30 years earlier, there was still more than 300,000 cases of polio each year worldwide due to errors in global coordination and lack of deployment in many countries. But, as a result of great efforts, the impact since then has been remarkable. Two of the three types of poliovirus (type 2 and type 3) have disappeared thanks to immunity from the vaccine. Only type 1 remains. The virus could be completely eradicated from the world. And we are close to seeing it disappear – in the last 12 months there were hardly 16 registered cases polio with paralysis caused globally by type 1 (a decrease from 176 cases in 2019).
This success has been largely due to the use of the oral vaccine and the live Sabin virus, which anyone over the age of 18 has received through drops in the mouth or, like me, perhaps remembers with honey in the form of a dose in a sugar cube. This vaccine is especially good at preventing disease and stopping transmission of the virus. It has already stopped polio in most of the world. There are enormous efforts to eradicate it, which focus on improving vaccine coverage in the few countries where the virus is still found. The greatest attention is devoted to improving access in Afghanistan and Pakistan. It’s been 42 years since smallpox eradication. Is it time for polio? We’re not there yet, and there were some notable setbacks with cases in Malawi and Mozambican last year. But the end of another threat to history seems possible.
While polio eradication seems within reach, the path is not clear. Sabin’s live virus vaccine, which has been saving the world from polio for 70 years, can go through abnormal mutations on rare occasions, which paradoxically make the virus capable of causing paralysis in populations with low vaccination rates. However, the Sabin vaccine remains a critical part of the global program thanks to its ability to enhance the immune response, thereby reducing the spread of the wild-type virus. Now that polio is disappearing, more attention is being paid to preventing cases of paralysis caused by mutations of the Sabin virus.
don’t let your guard down
The most important part of the strategy is, perhaps counterintuitively, to improve vaccination coverage with the Sabin vaccine, since paralysis does not occur in populations with high vaccination rates. Many countries that have successfully eliminated the virus, generally using the live Sabin vaccine, have switched to using the Salk vaccine. The Salk contains a dead virus that cannot mutate or spread and has been part of the routine vaccination schedule in the United Kingdom since 2004. All children in the United Kingdom are offered five doses injectable Stalk polio vaccine during childhood.
The imported virus found in London sewers threatening children is a virus, and the risk can be eliminated if vaccination coverage is improved. Unfortunately, some of the lowest vaccination rates in the UK are in parts of London, in the same places where children are at risk of contracting this virus. The solution is simple, free and safe: Children who have missed or missed doses should be vaccinated as soon as possible.
Polio is not the only disease circulating that could be prevented with vaccines. And if we let down our guard and allow vaccination coverage to drop, it can hit us. Over the last decade, individuals with incomplete vaccinations in the UK have suffered from outbreaks of measles, mumps and diphtheria. Vaccines are immensely powerful in controlling contagious threats, but they only work if we use them.
* Professor Andrew Pollard is Director of the Oxford Vaccine Group, University of Oxford
Translation of Patricio Orellana