Poliomyelitis, also known as polio, is an infectious illness caused by a virus that attacks the nervous system and spinal cord, causing muscle weakness and ultimately paralysis. The poliovirus consists of an RNA genome and a protein capsid. It belongs to the species Enterovirus C. There are three different types of poliovirus: type 1, type 2, and type 3. The virus can spread from the faeces of an infected person to the environment and in the areas where there is poor sanitization, it spreads easily. Children under the age of 5 years are prone to poliovirus. One of the types of polio infections can cause paralysis as well. Thus to avoid getting infected by the virus a vaccine has been invented by Jonas Salk. Generally, the vaccination works by improving the immune system. As a result, the improvement of poliovirus immunity will improve the efficiency of poliovirus transmission control.
Polio Vaccine - History
John Kolmer and Maurice Brodie led two teams to create a poliovirus vaccine in 1935, and the findings were published in the American Public Health Association. Both of the vaccines were cancelled due to the death of the children who got vaccinated. Another scientist, John Kolmer, invented the vaccine and gave it to around 10,000 children, five of whom died and more than ten were paralyzed. In another town where polio was not found, the children were seriously affected, causing harsh responses from other researchers, one of whom nicknamed him "Kolmer a killer". Maurice Brodie reported his findings, however, the researchers were not pleased because of the Kolmer report; nonetheless, Brodie and his team designed the vaccine and tested it on themselves and infants, and as a result, he discovered that the vaccine was successful in about 88 per cent of cases.
At the Children's Hospital Boston, a research group that was led by John Enders cultivated the polio vaccine using human tissue. Another researcher named Thomas H. Weller, tried to develop the varicella virus in lung tissue, as a result of this, he extracted the sample of the brain of a mouse that was infected with poliovirus. Where the polio cultures are grown instead of varicella cultures. Thus all of them were recognized and awarded a Nobel prize for their work. Along with the improvement in the steps of finding vaccines the identification of serotypes of poliovirus added advantage to develop the vaccine.
The first effective polio vaccine was developed in 1952 by Jonas Salk with his team. A test called Francis Field Trial which is the largest medical experiment at that time was conducted by Thomas Francis utilized the Salk vaccine.
Types of Polio Vaccine
There are two types of vaccines that are used to fight and protect against the poliovirus.
Oral Polio Vaccine:
It is given with another name after its inventor Albert Sabin thus called the Sabin vaccine, in short, it is known as OPV that was introduced in 1961. It consists of three of the live attenuated serotypes of poliovirus. The serotypes include Sabin types 1, 2, and 3. These are selected for their ability to lower neurovirulence and reduced transmissibility. When the poliovirus type 2 was declared eradicated in 2015, there was the switching of the vaccine from trivalent (tOPV) to bivalent (bOPV). Trivalent had all the three types where the bivalent had only two types that are type 1 and 3.
The following are the administration OPV strains that produce an immune response to the primary site of the poliovirus replication that is the lining of intestines. Mucosal immunity provides a potential barrier to transmission by reducing the replication and excretion of the virus. This combination along with its affordability made the OPV vaccine a choice in the global eradication program.
Inactivated Poliovirus Vaccine:
It was first introduced in the year 1955. This is produced from poliovirus strains of wild-type, where each of its serotypes was inactivated with the help of formalin. It is an injectable vaccine and it can be taken alone or in combination with other vaccines such as hepatitis B, tetanus, diphtheria, etc. In a few countries such as the Netherlands and Scandinavia, the IPV vaccine has been used to eradicate the poliovirus. As it is a killed vaccine the risk of associating live virus with the use of OPV. Even now efforts are being made to develop the more suited poliovirus vaccine for the post-eradication environment. One example of such effort is the inactivated polio vaccine that was produced by the extraction of strains from Sabin.
Poliovirus is a communicable disease affected to humans by a virus called a human enterovirus. It can spread through contaminated water or food sometimes it may transfer from the saliva of an infected person. The patient that is exposed to many hazards can be found developing paralysis. Thus getting vaccinated is the best way to prevent the effect of poliovirus. It works by producing antibodies in the body against the virus. To fight against the virus, a large-scale government of India has started to provide immunization by launching a program where the vaccine has been provided orally in the form of polio drops.