The two vaccines that brought us to the brink of eradicating polio
- July 3, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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The two vaccines that brought us to the brink of eradicating polio
Sub: Science and tech
Sec: Health
Context:
- The wild poliovirus is restricted to pockets of Afghanistan and Pakistan, and is beginning to reappear from here in big cities in these two countries.
About Polio:
- Polio is also called Poliomyelitis.
- It is a viral disease that destroys the nerve cells present in the spinal cord, causing paralysis or muscle weakness to some parts of the body.
- It is a contagious disease affecting the nervous system and is caused by Picornaviridae – a poliovirus.
- The virus is transmitted by person-to-person through the following ways –
- 1) Through the fecal-oral route.
- 2) By contaminated water or food.
- This virus primarily grows and multiplies in the intestine, from where it can attack the nervous system and will cause polio and paralysis on an advanced level.
- In 1948, microbiologists John F. Enders, Thomas Weller, and Frederick Robbins were trying to find a method to grow different viruses in cell cultures.
- The poliovirus has only one natural host — humans — and many of the early strains of the virus were isolated from humans and wouldn’t infect non-human primates.
- The inability to culture polio in non-nerve cells was a major roadblock to developing a polio vaccine.
Eradication targets:
- Polio eradication is one of the top priorities of the World Health Organisation (WHO).
- Africa was declared polio-free in August 2020; the wild poliovirus has been restricted to rural pockets in Afghanistan and Pakistan.
- The WHO’s Global Polio Eradication Initiative is thus set to miss its deadline of eradicating polio by the end of 2024.
Various Polio vaccines:
Salk:
- Salk made the first successful vaccine for polio.
- It was an Injectable Polio Vaccine (IPV)
- Salk inactivated the virus by treating it with formaldehyde, and injected it into his test subjects.
- The fragments of the inactivated virus were able to induce immunity in their bodies.
- Since the vaccine was introduced into the muscle, it generated systemic immunity.
- The immune system has two main parts: the systemic and the mucosal.
- The systemic component includes the blood, the brain, and all other organ systems.
- The mucosal component includes the inner linings of the digestive and respiratory systems, the urogenital tract, and the eyes.
- These regions are lined with mucous membranes that provide an additional layer of protection, as they frequently come into contact with the external environment.
Sabin:
- Albert Sabin developed another vaccine that contained live polio strains weakened by growing them serially in macaque cells, making them unfit for human infection.
- This was the oral polio vaccine (OPV).
- OPV went into the stomach, it induced a powerful protective mucosal immune response right where the virus would have to begin its infection.
Advantages of OPV over IPV:
- The OPV vaccine induced a protective response at the viral entry site — the gut — allowing it to provide a much greater degree of protection relative to the IPV.
- The OPV was administered orally and didn’t require syringes or trained personnel for its administration.
Challenges in OPV:
- The weakened virus in the OPV would revert, and would do the very job it was designed to prevent: cause polio.
- The IPV, while being a less potent vaccine, contained inactivated virus particles and carried no risk of causing vaccine-induced polio.
- The world has used both vaccines in the fight against polio.
- While some countries, such as Norway, Sweden, Finland, and Iceland, relied exclusively on the IPV, most countries have used a combination of the two.
- The latter countries prefer the OPV for its superior protection and ease of administration.
- When the number of natural polio cases drops to zero, they switch to IPV for its enhanced safety.