Introduction:
Polio is a disease that plagued the 20th century and was feared by people globally. This report will explore the vaccine for polio and discuss the benefits and risks to conclude if the vaccine is worthwhile. The SHE concept “The use of scientific knowledge may have beneficial or unexpected consequences: this requires monitoring, assessment, and evaluation of risk, and provides opportunities for innovation,” will be considered and how it applies to the polio vaccine.
Biological Background:
A disease is a disorder of a function in an organism that produces specific symptoms that affect a specific part of the body (1). Polio (also known as poliomyelitis) is an infectious and extremely contagious disease caused by a virus that attacks the central nervous system, seen in figure 1 (2). British physician, Michael Underwood provided the first description of the disease in 1789 (3). The virus infects individuals by a pathogen invading a person’s brain and spinal cord, leading to paralysis (4).
Introduction:
Polio is a disease that plagued the 20th century and was feared by people globally. This report will explore the vaccine for polio and discuss the benefits and risks to conclude if the vaccine is worthwhile. The SHE concept “The use of scientific knowledge may have beneficial or unexpected consequences: this requires monitoring, assessment, and evaluation of risk, and provides opportunities for innovation,” will be considered and how it applies to the polio vaccine.
Biological Background:
A disease is a disorder of a function in an organism that produces specific symptoms that affect a specific part of the body (1). Polio (also known as poliomyelitis) is an infectious and extremely contagious disease caused by a virus that attacks the central nervous system, seen in figure 1 (2). British physician, Michael Underwood provided the first description of the disease in 1789 (3). The virus infects individuals by a pathogen invading a person’s brain and spinal cord, leading to paralysis (4).
The poliovirus is spread through contact with the stool of an infected person, or droplets from a cough or sneeze. A person could contract polio after contacting an infected person’s stool or droplets (6). The poliovirus enters the body through the mouth, and replicates in the gastrointestinal tract and throat, then moves into the bloodstream where it is carried to the central nervous system. Poliovirus then meets the nerve cells, specifically the motor neurons, and attaches to the surface receptors (seen in Figure 2) of the nerve cell which stimulates receptor mediated endocytosis and the virus is engulfed (7).
Viral RNA from the poliovirus enters the nucleus of the nerve cell and is replicated by viral RNA polymerase which forces the cell to produce more polioviruses. Replicated poliovirus particles are then released back into the bloodstream and can then infect other cells. Poliovirus attacks motor neurons which are responsible for the muscles that control swallowing, arms, legs, respiration and circulation, leading to muscle damage or paralysis (7).
The IPV (inactivated polio vaccine) is the most common vaccine for treating polio (9). IPV consists of killed poliovirus pathogen strains of all three poliovirus types which produces antibodies in the blood and lymph fluid which leads to the development of humoral immunity (10).
The vaccine works after the killed poliovirus particles are introduced into the body via injection into the arm, by the following steps.
1. The body reacts to the vaccine by macrophages identifying the antigens in the body.
2. The macrophages phagocytose the pathogen and display the antigens attached to their own major histocompatibility complex. Contact is made between the helper T cells and the macrophage with receptors complementary in shape to the antigen molecules. The macrophage releases a cytokine (Interleukin-1) which binds to the helper T cell.
3. The helper T cells release Interleukin-2 which activates the B cells, producing plasma cells and memory B cells.
4. The plasma cells secrete antibodies which have complementary binding sites to antigens, then bind to the poliovirus which destroys the virus.
5. The memory B cells and memory helper T cells formed stay in the body. If the body is ever invaded again by the poliovirus, the memory B cells and memory helper T cells leads the response to the pathogen invasion being faster and more massive, meaning the virus can’t infect the body (11).
After two doses of the IPV, it is 90% effective in protecting people against polio and after three doses the rate of immunity is even higher at 99%-100% effective (12).
Benefits and Risks:
A major benefit of the IPV to humans is that it triggers an effective protective immune response in most people and has been extremely successful in reducing polio outbreaks. IPV is one of the safest and most sanitary polio vaccines in use and no serious negative side effects have been found after the vaccination’s development, especially as sterile injection equipment and procedures are used (13).
Another benefit to humans of the IPV is, because it is a not a live vaccine, there is no risk of VAPP (vaccine associated paralytic polio) which means that there is no chance of developing polio after getting the vaccine (13).
Polio occurrence has dropped by 99% since the launch of global polio eradication efforts in 1988 and has decreased significantly since the introduction of the IPV vaccine in 1955, seen in Figure 3 (14). It is important to ensure that all children and adults are vaccinated against polio until is it completely eradicated in other countries to ensure that polio does not re-establish itself in Australia and the world.
A disadvantage of the IPV is that it produces very low levels of immunity in the intestine. As a result, the poliovirus in an infected person may still replicate inside the intestines and be shed in the faeces, leading to the risk of continued circulation of the virus (13).
Another disadvantage is that the IPV is over five times more expensive to produce than other polio vaccines such as the OPV (oral poliovirus vaccine). OPV was previously the main vaccine used to treat polio, however IPV is more widely used today as it is more effective and safer than the OPV (16).
A minor risk of the IPV is the possibility of a serious allergic reaction to the vaccine resulting in anaphylaxis. Side effects of the vaccine may include redness, swelling, pain or discomfort in the area that was injected with the vaccine, however these should pass in 2-3 days (17).
Conclusion:
The benefits of the inactivated polio vaccine are worth the risks, as it is a reliable, safe and effective vaccine for polio that has prevented the further spread of polio since its development and use. The side effects possible from the IPV are minor and serious allergic reactions are not likely to occur (18). This relates to the SHE concept as the innovation and evaluation of risk of the polio vaccines has led to the use of IPV being more common, compared to the IPV.
The poliovirus is spread through contact with the stool of an infected person, or droplets from a cough or sneeze. A person could contract polio after contacting an infected person’s stool or droplets (6). The poliovirus enters the body through the mouth, and replicates in the gastrointestinal tract and throat, then moves into the bloodstream where it is carried to the central nervous system. Poliovirus then meets the nerve cells, specifically the motor neurons, and attaches to the surface receptors (seen in Figure 2) of the nerve cell which stimulates receptor mediated endocytosis and the virus is engulfed (7).
Viral RNA from the poliovirus enters the nucleus of the nerve cell and is replicated by viral RNA polymerase which forces the cell to produce more polioviruses. Replicated poliovirus particles are then released back into the bloodstream and can then infect other cells. Poliovirus attacks motor neurons which are responsible for the muscles that control swallowing, arms, legs, respiration and circulation, leading to muscle damage or paralysis (7).
The IPV (inactivated polio vaccine) is the most common vaccine for treating polio (9). IPV consists of killed poliovirus pathogen strains of all three poliovirus types which produces antibodies in the blood and lymph fluid which leads to the development of humoral immunity (10).
The vaccine works after the killed poliovirus particles are introduced into the body via injection into the arm, by the following steps.
1. The body reacts to the vaccine by macrophages identifying the antigens in the body.
2. The macrophages phagocytose the pathogen and display the antigens attached to their own major histocompatibility complex. Contact is made between the helper T cells and the macrophage with receptors complementary in shape to the antigen molecules. The macrophage releases a cytokine (Interleukin-1) which binds to the helper T cell.
3. The helper T cells release Interleukin-2 which activates the B cells, producing plasma cells and memory B cells.
4. The plasma cells secrete antibodies which have complementary binding sites to antigens, then bind to the poliovirus which destroys the virus.
5. The memory B cells and memory helper T cells formed stay in the body. If the body is ever invaded again by the poliovirus, the memory B cells and memory helper T cells leads the response to the pathogen invasion being faster and more massive, meaning the virus can’t infect the body (11).
After two doses of the IPV, it is 90% effective in protecting people against polio and after three doses the rate of immunity is even higher at 99%-100% effective (12).
Benefits and Risks:
A major benefit of the IPV to humans is that it triggers an effective protective immune response in most people and has been extremely successful in reducing polio outbreaks. IPV is one of the safest and most sanitary polio vaccines in use and no serious negative side effects have been found after the vaccination’s development, especially as sterile injection equipment and procedures are used (13).
Another benefit to humans of the IPV is, because it is a not a live vaccine, there is no risk of VAPP (vaccine associated paralytic polio) which means that there is no chance of developing polio after getting the vaccine (13).
Polio occurrence has dropped by 99% since the launch of global polio eradication efforts in 1988 and has decreased significantly since the introduction of the IPV vaccine in 1955, seen in Figure 3 (14). It is important to ensure that all children and adults are vaccinated against polio until is it completely eradicated in other countries to ensure that polio does not re-establish itself in Australia and the world.
A disadvantage of the IPV is that it produces very low levels of immunity in the intestine. As a result, the poliovirus in an infected person may still replicate inside the intestines and be shed in the faeces, leading to the risk of continued circulation of the virus (13).
Another disadvantage is that the IPV is over five times more expensive to produce than other polio vaccines such as the OPV (oral poliovirus vaccine). OPV was previously the main vaccine used to treat polio, however IPV is more widely used today as it is more effective and safer than the OPV (16).
A minor risk of the IPV is the possibility of a serious allergic reaction to the vaccine resulting in anaphylaxis. Side effects of the vaccine may include redness, swelling, pain or discomfort in the area that was injected with the vaccine, however these should pass in 2-3 days (17).
Conclusion:
The benefits of the inactivated polio vaccine are worth the risks, as it is a reliable, safe and effective vaccine for polio that has prevented the further spread of polio since its development and use. The side effects possible from the IPV are minor and serious allergic reactions are not likely to occur (18). This relates to the SHE concept as the innovation and evaluation of risk of the polio vaccines has led to the use of IPV being more common, compared to the IPV.