In these times of pandemics, there should be little need to be reminded that there are some bad viruses out there, and they always have been. But emergency intervention to control epidemics and vaccine outbreaks is relatively new. The devastating polio epidemics of the 1940s and 1950s, which left thousands of children paralyzed in the UK, were very popular at the time, with familiar hospital images full of children with iron lungs like coffins or paralyzed children walking on calipers . These epidemics eventually disappeared in many countries as a result of the mass development of two different polio vaccines by Jonas Salk and Albert Sabin. Here, the success of the polio program led to the formation of the JCVI, the Joint Vaccination and Immunization Committee in 1963, and the development of a coordinated vaccination program that protects our children to this day. By the 1980s, despite the invention of the vaccine 30 years earlier, there were still more than 300,000 cases of polio each year worldwide due to global coordination failures and lack of development in many countries. But as a result of enormous efforts, a remarkable effect has been observed since then. Two of the three types of wild polio virus (type 2 and type 3) became extinct due to the immunity of the vaccine. only type 1 is left. It may be possible to completely eradicate this virus from the world. And we are very close to seeing the back – in the last 12 months there have been only 16 documented cases of paralytic polio caused by the rest of the type 1 virus worldwide (out of 176 cases in 2019). This success is largely due to the use of the live oral Sabin vaccine, which anyone over the age of 18 will have taken as oral drops or, like me, will fondly remember as a dose on a sugar cube. This vaccine is especially good at preventing disease and also at stopping the spread of the virus. It has already stopped polio in most parts of the world. Huge efforts are being made to eradicate, focusing on improving vaccine coverage in the few remaining countries where the virus is still present, with a greater focus on improving access to Afghanistan and Pakistan. It has been 42 years since the eradication of smallpox, could it be time for polio? We are not there yet and there have been some notable failures with cases in Malawi and Mozambique in the last year, but the end of another threat in history seems likely. While we are temptingly close to eliminating wild polio, it is not easy. The live Sabin vaccine, which has saved the world from polio epidemics for 70 years, can very rarely undergo horrible mutations, which paradoxically enables it to cause paralysis in unvaccinated populations. However, the Sabin vaccine remains a critical part of the global program due to its special properties in improving the immune responses in the gut and thus in reducing the spread of wild polio. Now that polio is in remission, more attention is being paid to avoiding rare cases of paralysis caused by mutated Sabin viruses. The most important part of the approach is, perhaps, on the contrary, improving vaccine coverage with the Sabin vaccine, as paralysis does not occur in populations with high immunity. Many countries that have been able to eradicate the virus, usually using the live Sabin vaccine, have switched to using the Salk vaccine. The Salk vaccine contains a dead virus that cannot be mutated or spread and has been part of the routine vaccination program in the UK since 2004. All children in the UK are offered five doses of the Salk childhood polio vaccine. It is an imported Sabin virus in sewage in London that threatens children there and the risk can be eliminated by improving vaccine coverage. Unfortunately, some of the lowest coverage vaccines in the UK are found in some parts of London, in the very places where children are at high risk for this virus. The solution is simple, free and safe: children who have not received a dose or have missed it should be vaccinated as soon as possible. Polio is not the only disease that can be prevented with vaccines and it can strike if we let go of our alertness and let the vaccine coverage fall. Outbreaks of measles, mumps, and diphtheria have been reported in immunocompromised individuals in the United Kingdom over the past decade. Vaccines are extremely powerful in controlling infectious threats – but they only work if we use them.
