Overview

Polio (Poliomyelitis) is a disease caused by the poliovirus. The poliovirus is spread from contaminated food or water or via faecal-oral routes, meaning it can spread if an infected person doesn't wash their hands after going to the toilet. It is highly infectious and tends to affect children 5 years old and under. Due to the Global Polio Eradication Initiative, polio is almost entirely eradicated, and your chances of catching it are incredibly low. Poliovirus types 2 and 3 were eliminated in 1999 and 2020, respectively, however, poliovirus type 1 still remains in Afghanistan and Pakistan. Vaccinations have been pivotal in eradicating polio and preventing further spread when cases arise.

Poliovirus

Polio is caused by the poliovirus, which spreads via contaminated food or water or from person to person via the faecal-oral route. Most people who get polio do not have symptoms, however, you can experience mild flu-like symptoms, such as headaches, fever, muscle pain, and fatigue. In more serious cases, polio can affect the brain and the nerves, which can lead to paralysis. If paralysis affects the muscles that you need to breathe, you are at risk of death. In most cases, paralysis is short-term, and you regain your movement, however, some people can be left with a permanent disability. Generally, the virus affects the gut, oesophagus (connection between throat and stomach), and pharynx (throat), where it causes fever-like symptoms. However, when the virus enters the central nervous system, including the motor neurons, a patient could experience paralysis.¹

Vaccination for the eradication of polio

In the UK, a child will receive 5 polio vaccines up until the age of 14 to ensure they are fully vaccinated against the disease. There are two general types of polio vaccines: the inactivated polio vaccine (IPV) and the oral polio vaccine (OPV).

Oral vaccine

The oral polio vaccine is a weakened form of the virus given orally to patients. Generally, two types of poliovirus, type 1 and type 3, are included in this vaccine to confer immunity against them. The weakened viruses replicate in the intestine, and the body will generate an immune response and immunological memory, which means the person is protected from future infections of polio. Importantly, the oral polio vaccine can cause passive immunisation because the virus is present in the faeces of the vaccinated individuals and can spread to others in contact. In rare cases, the weakened virus reverts to a wild form and can cause the disease again.  However, this can cause issues in areas where vaccine uptake is low.

Inactivated vaccine

The inactivated polio vaccine (also known as the Salk vaccine) contains inactivated viruses of all three polio types and is delivered via injection. Whilst this vaccine confers protection against all poliovirus types, because of its different route of administration, it does not stimulate strong immunity. Therefore, a person could be at risk of catching poliovirus because it will be able to replicate. The vaccinated person will have antibodies present to prevent the wild polio from causing any symptoms of serious infection. However, they will still shed the virus in their faeces, allowing it to spread. Therefore, this vaccine will not prevent the spread of polio, unlike the oral vaccine, which prevents wild poliovirus from infecting you.

Why did polio spread in low-vaccination areas

Polio tends to spread more easily in areas with poor hygiene and sanitation systems. Areas facing political instability and war are considered at risk of polio outbreaks.² In the summer of 2024, a case of polio was reported in Gaza, and subsequently, a WHO vaccination scheme was introduced to protect the children living in Gaza from contracting polio.

Whilst polio cases are rare in the wider world, low vaccination rates threaten this level of security. If people are not vaccinated against polio, they risk catching the virus and spreading it to people around them. 

Herd immunity arises when the majority of the population is vaccinated against viruses or bacteria that cause a specific disease. If a greater proportion of the population is vaccinated, fewer people will become infected with the disease, meaning it is less likely to spread. Therefore, herd immunity can protect unvaccinated people. The oral polio vaccine is better at preventing spread than the inactivated polio vaccine because of the type of immunity it causes and, therefore, is better for herd immunity.³ 

In areas where vaccine uptake is lower, there are fewer vaccinated people to help prevent the spread of poliovirus to unvaccinated people and, therefore, these areas are at risk of outbreaks.

Vaccine-derived poliovirus (VDPV) is a mutated version of poliovirus from the weakened virus in the oral polio vaccine. This version could spread around communities that are not fully vaccinated, in areas where hygiene and sanitation are poor, or where there is a lot of overcrowding. Vaccination is very important in this instance, as the more people VDPVs can infect, the greater the chance they have of mutating further.

Factors contributing to low vaccination uptake

So why is vaccine uptake low? There are many complex reasons behind low vaccine uptake, some of which will be discussed further; however, this is by no means an exhaustive list of reasons why people may choose not to get vaccinated. 

Misinformation has been shown to be linked to low vaccine uptake.⁴ Inaccurate information shared online and via word of mouth can cause people to be hesitant in getting themselves and their children vaccinated. Naturally, this poses a serious risk to public health. Refer to trusted information sources, such as the NHS or WHO websites, or speak to medical professionals to better understand the vaccines you are taking. 

Issues with access to healthcare could provide another reason for low vaccination uptake. In some cases, people may be too far from vaccination centres or struggle to get transport to vaccination clinics. Furthermore, childcare duties, associated costs, and physical accessibility barriers are also reasons why inaccessible healthcare can lead to lower vaccination uptake.

A global survey found that higher levels of vaccine uptake were associated with increased trust in healthcare workers compared to non-medical sources of information, including friends and family.⁵ Mistrust of health services and healthcare professionals can lead to vaccine hesitancy and lower levels of immunisation, ultimately putting public health at risk.

War and political unrest are other key reasons for lower vaccine uptake.⁶ Unrest can lead to overcrowding, poor sanitation and a loss of access to healthcare, meaning people are unable to get the vaccines they need to prevent the spread of such damaging diseases.

Summary

Although polio is a rare disease, it is still present in the modern world, and there is always a risk of outbreaks emerging. To protect yourself and those around you, it is important that you get yourself and your loved ones fully vaccinated. Whilst some types of polio have been eradicated, others remain, and it is all of our duties to do what we can to keep them at bay. Misinformation, mistrust and inaccessible healthcare can lead to lower vaccination uptake. War and political unrest are other key reasons, mainly due to their poor sanitation. If you wish to know more about polio and the polio vaccines, please consult trusted information sources or speak to a medical professional. 

FAQs

Is polio eradicated?

No, poliovirus remains in Afghanistan and Pakistan and could be imported to other countries, spreading among unvaccinated populations 

Do I need to vaccinate against polio?

Yes, vaccines are the best way to prevent an infection by the poliovirus 

Who should receive the vaccine?

Children under 5 years old are the ones receiving a vaccination scheme because they are at higher risk of catching the disease. However, adults in regions where polio is still present may require a booster

Is the polio vaccine effective?

Three doses of the IPV vaccine provide at least 99% protection