Polio is perhaps the last pediatric illnesses you will think of when you have a baby since it is almost non-existent except in a few pockets of the world. Polio is capable of causing life-long complications, but it is also one of the easiest diseases to prevent.
Polio vaccines have become more pervasive than the disease itself. But what causes polio in the first place and what is the vaccine called? MomJunction tells you about polio and the schedule of vaccination to keep your child safe.
What Is Polio And What Causes It?
Polio, also called poliomyelitis and infantile paralysis, is an infectious disease that primarily affects the digestive system and the nervous system of the body (1). The disease is caused by a virus called poliovirus that transmits rapidly and only affects human beings (2).
Polio is a highly contagious disease and mostly strikes children below the age of five years. The ability of the disease to cause irreversible, life-long damage to the body is what makes it one of the most concerning pediatric illnesses.
How Does Poliovirus Transmit?
The poliovirus transmits via the oral or respiratory routes, through:
- Contaminated food and water: Food and water contaminated with fecal matter of an infected person can spread the virus. The virus can pass into the bloodstream via the intestine, from where it can travel to any part of the body.
- Poor hygiene: Not washing hands after using the toilet can transmit the virus from person to person. The poliovirus can thrive in feces for several weeks. Not washing hands immediately after coming into contact with soil contaminated with human fecal matter can also cause its transmission.
- Inhalation of sneeze or cough droplets: You can get the virus if you’re standing close to infected persons when they are sneezing or coughing, although that is less common than fecal contact. The virus moves through the body by passing into the bloodstream from the lungs.
How Long Can An Infected Person Transmit The Disease?
A person is infectious for about seven to ten days after the onset of the symptoms (3). The virus persists in the throat for about a week after the person contracts it and can be passed through feces for up to six weeks. Nevertheless, a person with polio may transmit the disease any time during the term of illness.
What Are The Symptoms Of Polio?
The majority of individuals who suffer from polio do not display significant symptoms of the infection (4). About 25% of patients, or one in four persons, may show the following early signs of polio illness:
- Sore throat
- Nausea and stomach pain
- Tiredness and chronic fatigue
These flu-like symptoms last for only two to five days. But it is the long-term symptoms, which emerge later, that cause the most discomfort to the affected person.
- Meningitis: The poliovirus proliferates the nervous system, reaches the brain and spinal cord where it infects the meninges – the layer covering the brain and spinal cord. One in 25 affected individuals displays this symptom.
- Paresthesia: It is the feeling of numbness, tingling or burning sensation in the hands and feet. Chronic paresthesia occurs due to nerve damage (5), which is quite common among those with polio.
- The chronic stiffness of muscles: About 1-2% of infected individuals display severe stiffness along with pain, primarily of the muscles in the neck and the back.
- Poor muscle control: Polio patients can also display poor control of skeletal muscles leading to limited movement of the body.
If the child displays the symptoms mentioned above, consult a doctor without delay. The doctors may suggest a blood and stool test to check for the virus. But rather than wait for the symptoms to show, take steps to prevent the disease.
How To Prevent Polio In Children?
Vaccination is the most reliable way to prevent polio infections (6). Several nations that have been polio-free for decades still administer the vaccine. An example of this is the Pulse Polio Vaccine campaign in India, which was declared polio-free in the year 2014 (7).
While good hygiene and sanitation can help minimize the spread of the virus, they are not as effective as the poliovirus vaccine in preventing the disease. Vaccination also protects your child when you are traveling to regions where the virus is still active.
How Does Vaccine Help Prevent Polio?
Polio vaccine helps build immunity by introducing a small quantity of inactive poliovirus to the body. The body then builds its antibodies that stay for a lifetime. Future infection is averted thanks to the active immunity induced by the polio vaccine.
According to the World Health Organization (WHO), vaccination has brought down the number of polio cases across the world by more than 99% since 1988, thus saving the lives of more than 16 million people (8). However, even a single unvaccinated child has the potential to cause a relapse of the polio epidemic, leading to spread of the virus across the globe in less than ten years.
So, get your child vaccinated against polio to keep them safe and also to prevent the spreading of the virus.
What Are The Types Of Polio Vaccines?
There are two types of polio vaccine:
1. Oral poliovirus vaccine (OPV):
It is an orally administered polio vaccine that is popularly used around the world, owing to its ease of use. The vaccine is made from biologically restrained poliovirus, which is 10,000 times less potent than the wild poliovirus (9).
The weak proliferative abilities of the virus prevent it from escaping the digestive system, where it is eventually destroyed by antibodies. The immune system retains the antibodies that offer lifelong polio immunity.
OPV was earlier available as monovalent oral poliovirus vaccine (mOPV) for one strain of poliovirus or bivalent oral poliovirus vaccine (bOPV) for any two strains of poliovirus. But modern OPVs are all trivalent OPV (tOPV), which protect against all three strains of poliovirus.
2. Inactivated poliovirus vaccine (IPV):
It is also called the Salk vaccine, named after Dr. Jonas Salk, who developed the vaccine in 1955. IPV is made from inactivated viruses of all three poliovirus strains and has to be administered into the muscle (intramuscular) or below the skin (intradermal) (10).
IPV needs to be administered by a trained healthcare professional, through a sterile needle. It is the preferred polio vaccine in several developed nations and the only type available in some countries such as the US (11).
Advantages and disadvantages of OPV and IPV
|Oral Poliovirus Vaccine (OPV)|
|Low cost||Requires several doses; more the better|
|Easy and quick to administer||In rare cases, may cause paralysis if the child is severely immunodeficient|
|No syringe means less risk of other infections||In sporadic cases, the virus may mutate and cause polio epidemic|
|Can be administered by any trained person|
|Develops rapid intestinal immunity|
|The restrained virus may spread in the environment, providing passive immunity to others|
|Inactivated Poliovirus Vaccine (IPV)|
|Safest since no live viruses used||High cost; five times costlier than OPV|
|No risk of the baby developing paralysis||Has to be administered by a healthcare professional/doctor|
|First and only choice in most developed nations||Sterile equipment and environment needed for administration|
|Slow induction of immunity. Also, cannot provide passive immunity across communities|
Despite the above facts, OPV and IPV are approved by premier healthcare bodies like the WHO and US Centers for Disease Control and Prevention (12). The vaccine you get depends on what’s available in your region and the recommendation of the government.
How Often Should A Child Get Polio Vaccine?
The number of immunization doses or shot depends on the type of poliovirus vaccine you get.
Oral poliovirus vaccine (OPV)
One dose of OPV consists of two drops of vaccine given at the following ages (13):
- Birth: Zero dose
- Six weeks: First primary dose
- Ten weeks: Second primary dose
- 14 weeks: Third primary dose
- 18 weeks: Extra “+1” dose
Four OPV doses are sufficient to provide complete immunity, but children living in hot and humid regions such as the tropics, need more than four doses to ensure immunity. Therefore, the WHO recommends administering additional doses regularly even after the child gets the first four doses (14).
Inactivated poliovirus vaccine (IPV)
IPV is injected into the leg or the arm depending on the age of the child. There are only four shots of IPV:
- Two months: First shot
- Four months: Second shot
- 6-18 months: Third shot
- 4-6 years: Booster shot
Three IPV shots provide 99% immunity, and the one booster shot helps make it 100%. It is imperative that you get all shots since missing even one dose can leave the child susceptible to polio.
Is It Safe To Give Multiple OPV Doses?
Yes. You can give more than four OPV doses to a child. There is no risk of overdose, and a child can get more than ten doses of OPV until the age of five years. For this reason, it is recommended to get the child vaccinated on the National Immunization Day every year, until they are at least five years old.
What Is The Age Limit For Polio Vaccine?
Your child should get the booster shot by the age of six years. However, if you have missed any of the IPV shots or the IPV booster shot, you can get the child vaccinated even after the age of six years. There is no limit on the dosage of OPV, which means you can get as many doses as deemed necessary, even after the child is older than six.
Can A Child Have Polio Vaccine When Sick?
Yes. You can get a dose of OPV or IPV even when your child is unwell. The two vaccines are safe even for newborn infants. However, if the child is infected with HIV, then it is best to stick to IPV since OPV uses live viruses, and the vaccine elicits a poor response from an HIV-infected immune system (15).
There is also a risk of polio infection and paralysis in HIV-infected individuals. For these reasons, the WHO and the US Department of Health and Human Services recommend using IPV for children who have HIV (16) (17).
Does Polio Vaccine Have Side-effects?
The side-effects of oral and inactivated poliovirus vaccines are rare and often occur in specific situations.
Side-effects of oral poliovirus vaccine (OPV)
- Vaccine-associated paralytic poliomyelitis (VAPP): VAPP happens when the weakened poliovirus mutates to a toxic form of the virus causing a polio infection and subsequent paralysis. But VAPP is rare and occurs in about one in 2.4 million OPV immunizations (18). VAPP is mostly seen in immunodeficient children and adults who get immunized with OPV.
- Circulating vaccine-derived poliovirus: In rare instances, the weakened virus in the OPV may mutate and take a potent virulent form that rapidly transmits like wild poliovirus. This usually happens in communities that are under-immunized, with individuals who have skipped several OPV dosages. Vaccine-derived poliovirus is also mostly observed in regions with poorest sanitation practices (19).
Inactivated poliovirus vaccine (IPV) side-effects
- Soreness and pain at the injection site: Since the injection is intramuscular or intradermal, the child may experience pain and discomfort for several days after the vaccination. Sometimes, the entire limb may feel painful. But the pain subsides after some days and does not cause any long-term problems.
- Risk of wild poliovirus infection: Since IPV induces low immunity until the third dose, a child can still contract poliovirus despite getting a couple of IPV shots. Therefore, it is vital to remember that your child is vulnerable to polio at least till they complete three doses of IPV, which is between the ages of 6-18 months.
Is Polio Treatable?
No. There is no treatment for polio. Prevention is the only way to avoid the disease (20).
Are There Long-Term Complications Of Untreated Polio?
Yes. Polio can cause long-term complications when left untreated. The following are the acute complications of the illness:
- Paralysis: About one in 200 (0.5%) cases of polio result in irreversible paralysis. Those who survive the illness live with a damaged nervous system, which is unable to replace the nerve cells damaged by the virus (21). It can also lead to paralysis in the long-term.
- Joint and muscle deformities: Muscle and joint deformities are perhaps the most instantaneously recognizable signs of polio. Destruction of neurons causes abnormal muscle contraction that eventually leads to deformities of the joints. In the long term, there is also progressive muscle loss, which restricts movement (22).
- Post-polio syndrome: Polio survivors can develop excessive muscle loss, pain in muscles and joints, breathing and swallowing problems, and chronic fatigue. This condition is called post-polio syndrome or progressive post-polio muscular atrophy (PPMA) (23). PPMA symptoms may emerge years, even decades, after surviving polio and living a stable, healthy life. PPMA is most likely to occur in old age; after crossing the age of 70 years. As the name suggests, the condition is progressive and usually deteriorates the health of the individual.
About 5-10% of polio patients may not survive the illness due to paralysis of the breathing and swallowing muscles. In spite of the permanent complications, polio is easily preventable.
When everyone in the society is immunized, the poliovirus has no chance of survival (24). The OPV or IPV doses are not very expensive and are often provided for free or at subsidized prices by the public health departments.
So the next time there is a polio vaccination drive, make sure to take your child. In case you missed the date, you can always ask your healthcare provider for an immunization.
Have anything to share about preventing polio in children? Tell us in the comments section.