But the oral vaccine also came with a small risk: It can cause new cases of the disease. But if immunization is spotty, and if sanitation is lacking as the virus is often passed through the gut into sewer systems , vaccine-derived polio can continue to spread for years. Transmission of vaccine-derived polio works like this: A person swallows the oral vaccine, which contains a live, weakened virus.
That virus can live in the gut for a while, and then pass from person-to-person, developing mutations along the way. In , the Polio Global Eradication Initiative phased out the use of the polio type-2 oral vaccine. The Eradication Initiative would like to ideally phase out all oral vaccines by , and replace them with injectable vaccine. The injectable vaccines contain a dead virus that cannot cause polio, but they are more expensive and harder to administer.
Compare that to the numbers of wild polio virus cases: Afghanistan has seen eight this year, and Pakistan, three. In , there were 96 cases — globally — of vaccine-derived polio and just 22 cases from the wild virus. The outbreak just needs to attract enough attention and political will.
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Infected people who don't have any symptoms can still pass polio on to others. There have been rare cases where polio has been caused by being vaccinated with a live version of the polio virus. This is no longer a risk in the UK because the vaccine used nowadays contains an inactive version of the virus. As a result of routine vaccination programmes, polio has been largely wiped out in most parts of the world.
This includes Europe and the Americas. You can use the country guide on the Travel Health Pro website to check if there's a risk of getting polio in a country you plan to visit.
There's currently no cure for polio. Treatment focuses on supporting bodily functions and reducing the risk of long-term problems while the body fights off the infection. This can include bed rest in hospital, painkillers, breathing support and regular stretches or exercises to prevent problems with the muscles and joints.
If you're left with long-term problems as a result of a polio infection, you'll probably need ongoing treatment and support. This may include physiotherapy to help with any movement problems, devices such as splints and braces to support weak limbs or joints, occupational therapy to help you adapt to any difficulties, and possibly surgery to correct any deformities.
The polio vaccination is offered as part of the NHS routine childhood vaccination programme. If you're planning to travel to a polio-affected country, you should get vaccinated if you've not been fully vaccinated before, or have a booster dose if it's been 10 years or more since your last dose of the vaccine.
You can also get vaccinated at any point if you haven't been fully vaccinated before, even if you're not travelling somewhere where there's a risk of infection. If you've had polio in the past and haven't been vaccinated, it's still recommended that you get fully vaccinated. This vaccine, a decade in the making, has been tested for safety and efficacy, but is not yet licensed and still has to undergo further trials. The WHO is in the last stages of considering whether to approve it more quickly, under what is called an emergency-use listing — a procedure that was created during the —16 Ebola outbreak in West Africa, and which the agency is also preparing to use for coronavirus vaccines.
Most cases of cVDPV are caused by mutations in a strain of poliovirus called type 2. Right now, outbreaks are being tackled using the old vaccine for type 2 polio — which risks seeding further outbreaks. The initiative is a partnership between the WHO and international donors.
Results from phase I trials of the vaccine were published last year 1. Two phase II trials have been completed, but results are as yet unpublished. However, manufacturer Bio Farma, headquartered in Bandung, Indonesia, has produced million doses in anticipation that the WHO will grant an emergency-use listing while further trials are in progress.
Medical researcher Albert Sabin developed the conventional polio vaccine in the s and s, by growing the virus in non-human primates and cell cultures, until it adapted to those environments and was no longer good at infecting humans. The vaccine must be taken by mouth, and recipients excrete the live virus in their faeces for a period afterwards. If this virus is ingested by other people, for example in contaminated drinking water, it can infect them. This is usually harmless, because the virus is attenuated.
And it could even boost immunity against polio, just as it does for those who receive the vaccine directly. But what Sabin never knew, says Raul Andino, a virologist at the University of California, San Francisco, was that his attenuation of the virus hung by a thread. And this happened — possibly as early as , when an outbreak of polio derived from a vaccine began in Egypt.
More cases emerged in later years, even though wild polio was on its way to being eliminated in most countries. A crucial moment came in , when wild polio type 2 was declared to have been eradicated, 16 years after the last case was reported.
And for a bacterial pathogen, antibiotic treatments can target the disease itself. For a sense of what actually works, smallpox provides the perfect case study: It turns out to be almost ideally suited to eradication. Second, the disease makes its presence clearly and unambiguously known. These traits make it easier to track new cases and quickly stop outbreaks. Third, smallpox has a highly effective vaccine, made from a virus closely related to smallpox called the vaccinia virus.
Because the vaccine contains a live virus, the immune system produces a rapid, strong and lasting response. The vaccine can even stop a smallpox infection in its tracks. The vaccine made it easier to halt new transmissions and protect healthy people, even if responders arrived at a smallpox outbreak that was already underway. The fourth reason — and an increasingly relevant one — is not a biological consideration, but a psychological one: Smallpox was a feared disease. People knew it was deadly, and even survivors could be scarred for life.
This translated to political support from world governments and local support among populations receiving the vaccination. But if a disease is missing just one or two of these attributes, it can prove much harder to eradicate. Like smallpox, polio is a disease that only affects humans, and we have an effective vaccine for it.
In fact, we have two.
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