Active Immunization- Advantages and Drawbacks
Active immunization is a process of stimulating the body`s immune system to produce antibodies and memory cells that can protect against specific infectious diseases. It can be achieved naturally by exposure to a pathogen or artificially by vaccination. Active immunization is different from passive immunization, which involves transferring antibodies from another source to provide temporary immunity. Active immunization has the advantage of being long-lasting and can be reactivated by a booster dose or a natural infection. However, it also has some drawbacks, such as requiring time to develop, being ineffective in some immunocompromised individuals, and having potential side effects or complications. In this article, we will discuss the various aspects of active immunization, including its types, routes, purpose, examples, advantages and drawbacks.
Active immunization is the process of stimulating the immune system to produce antibodies and memory cells against a specific infectious agent. This results in long-lasting immunity that can protect the individual from future infections by the same agent.
Active immunization can be acquired in two ways: naturally or artificially.
Natural Active Immunization
Natural active immunization occurs when an individual is exposed to an antigen or pathogen in the environment and develops an immune response. For example, an individual who recovers from a first case of the measles is immune to further infection by the measles-causing virus, because the virus stimulates the immune system to produce antibodies that specifically recognize and neutralize the pathogen the next time it is encountered.
Natural active immunization is usually acquired through natural infection, but it can also occur through cross-reactivity with other antigens or pathogens. For example, some individuals who have been infected with cowpox virus are immune to smallpox virus, because the two viruses share some common antigens that elicit a cross-reactive immune response.
Natural active immunization has some advantages and disadvantages. On one hand, it provides long-term immunity that is specific and effective against the pathogen. On the other hand, it can also cause severe illness or complications in some cases, especially for individuals who are immunocompromised or have underlying health conditions. Moreover, natural active immunization may not be available or feasible for some pathogens that are rare, highly virulent, or have no effective treatment.
Artificial Active Immunization
Artificial active immunization occurs when an individual is given a vaccine that contains a nontoxic antigen preparation that infers protective immunity by inducing a memory response to an infectious microorganism. The vaccine may contain live attenuated or killed microorganisms or parts or products from them capable of stimulating a specific immune response comprised of protective antibodies and T cell immunity.
Artificial active immunization is usually performed as a prophylactic measure to prevent infection by a specific pathogen before exposure to it occurs. The purpose of vaccination is to ensure that a large enough number of antibodies and lymphocytes capable of reacting against a specific pathogen or toxin are available before exposure to it occurs.
Artificial active immunization can be induced via two different routes: systemic immunization or mucosal immunization.
Systemic immunization involves injecting the vaccine subcutaneously or intramuscularly into the deltoid muscle. This route delivers the vaccine into the bloodstream and lymphatic system, where it can reach the systemic immune cells and organs. Examples of systemic vaccines include those for measles, mumps, rubella, pneumococcus, meningococcus, and haemophilus infections.
Mucosal immunization involves administering the vaccine through the mucosal route as the site of choice for immunization either orally or through the nasal associated immune tissue (NALT). This route delivers the vaccine into the mucosal surfaces and tissues, where it can reach the local immune cells and organs. Examples of mucosal vaccines include those for polio, rotavirus, cholera, and influenza.
Artificial active immunization has some advantages and disadvantages. On one hand, it provides a safe and effective way of inducing immunity against a specific pathogen without causing disease or complications. On the other hand, it may require multiple doses or boosters to maintain adequate immunity levels. Moreover, artificial active immunization may not be suitable for protection of immuno-compromised or immuno-deficient individuals who may not respond well to vaccines.
Vaccines are preparations that contain antigens derived from a specific pathogen or a synthetic substitute. They are designed to stimulate the immune system to produce a protective response against the pathogen without causing the disease. There are different types of vaccines based on the nature and source of the antigens, such as:
- Live attenuated vaccines: These vaccines contain live but weakened versions of the pathogen that can replicate in the host but do not cause disease. They induce a strong and long-lasting immune response that mimics natural infection. Examples of live attenuated vaccines are those for measles, mumps, rubella, chickenpox, and yellow fever.
- Inactivated vaccines: These vaccines contain killed or inactivated forms of the pathogen or its components that cannot replicate in the host. They induce a weaker immune response than live attenuated vaccines and may require multiple doses or boosters to maintain immunity. Examples of inactivated vaccines are those for polio, hepatitis A, rabies, and influenza.
- Subunit vaccines: These vaccines contain purified or recombinant antigens from the pathogen that are sufficient to elicit an immune response. They have a lower risk of adverse reactions than whole-cell vaccines but may also require multiple doses or adjuvants to enhance their efficacy. Examples of subunit vaccines are those for hepatitis B, human papillomavirus (HPV), and pertussis.
- Conjugate vaccines: These vaccines link polysaccharide antigens from the pathogen`s capsule or cell wall to a protein carrier that enhances their immunogenicity. They are especially useful for inducing immunity against bacteria that have polysaccharide capsules that are poorly recognized by the immune system. Examples of conjugate vaccines are those for Haemophilus influenzae type b (Hib), meningococcus, and pneumococcus.
- Toxoid vaccines: These vaccines contain inactivated toxins produced by certain bacteria that cause disease by their toxic effects. They induce immunity against the toxin rather than the bacteria itself. Examples of toxoid vaccines are those for tetanus and diphtheria.
- DNA vaccines: These vaccines contain plasmids or circular pieces of DNA that encode antigens from the pathogen. They are injected into the host`s cells where they produce the antigens and stimulate an immune response. They have the potential to induce both humoral and cellular immunity and are easy to produce and store. However, they are still experimental and not widely used in humans. Examples of DNA vaccines are those for HIV and malaria.
- RNA vaccines: These vaccines contain messenger RNA (mRNA) molecules that encode antigens from the pathogen. They are delivered into the host`s cells where they are translated into proteins and stimulate an immune response. They have the advantage of being safe, stable, and adaptable to different pathogens. They have been recently developed and approved for use against COVID-19. Examples of RNA vaccines are those developed by Pfizer-BioNTech and Moderna.
These are some of the main types of vaccines that are used for active immunization against various infectious diseases. Each type has its own benefits and limitations depending on the nature of the pathogen, the mode of transmission, the availability of resources, and the safety and efficacy of the vaccine.
Artificial active immunization is the process of inducing immunity to a specific infectious agent by administering a vaccine that contains a nontoxic antigen preparation derived from the agent. Depending on the type and location of the infection, artificial active immunization can be performed via two different routes:
Systemic immunization: This involves injecting the vaccine subcutaneously or intramuscularly into the deltoid muscle or other suitable sites. The vaccine is then transported by the blood to various lymphoid organs, where it stimulates the production of antibodies and T cells that can recognize and eliminate the pathogen. Systemic immunization is suitable for preventing infections that affect the whole body or multiple organs, such as measles, mumps, rubella, pneumococcus, meningococcus, and haemophilus infections. Systemic vaccines are usually given in multiple doses to ensure adequate and long-lasting immunity.
Mucosal immunization: This involves delivering the vaccine to the mucosal surfaces of the body, such as the mouth, nose, or intestines. The vaccine is then taken up by specialized cells called M cells that transport it to the underlying lymphoid tissues, where it activates the mucosal immune system. The mucosal immune system consists of antibodies and T cells that can protect the mucosal surfaces from invasion by pathogens. Mucosal immunization is suitable for preventing infections that affect the mucosal surfaces or enter through them, such as polio, rotavirus, cholera, and influenza. Mucosal vaccines are usually given orally or nasally and may confer local as well as systemic immunity.
Both routes of artificial active immunization have their advantages and disadvantages. Systemic immunization can induce a strong and durable immune response that can protect against systemic infections. However, it may not be effective against mucosal infections, since the systemic immune system may not reach or respond to the antigens present at the mucosal surfaces. Moreover, systemic immunization may cause adverse reactions such as pain, swelling, fever, or allergic reactions at the injection site or elsewhere in the body.
Mucosal immunization can induce a local immune response that can protect against mucosal infections. It may also induce a systemic immune response by stimulating cross-talk between the mucosal and systemic immune systems. Furthermore, mucosal immunization may be more convenient and acceptable than systemic immunization, since it does not require needles or injections and may mimic natural exposure to pathogens. However, mucosal immunization may not be effective against systemic infections, since the mucosal immune system may not reach or respond to the antigens present in other parts of the body. Moreover, mucosal immunization may face challenges such as degradation of antigens by digestive enzymes or low uptake by M cells.
Therefore, choosing the appropriate route of artificial active immunization depends on several factors, such as the nature and location of the infection, the availability and safety of the vaccine, and the preference and compliance of the recipient. In some cases, a combination of both routes may be beneficial to achieve optimal protection against a specific infectious agent.
The main purpose of vaccination is to prevent or reduce the risk of infectious diseases by stimulating the body`s own immune system to produce protective antibodies and memory cells. Vaccination can protect not only the individual who receives the vaccine, but also the community as a whole by reducing the spread of pathogens and creating herd immunity. Herd immunity occurs when a large proportion of the population is immune to a disease, either through natural infection or vaccination, and thus provides indirect protection to those who are not immune. This can prevent outbreaks and epidemics of diseases that can cause serious complications and deaths, especially among vulnerable groups such as infants, elderly, and immunocompromised people.
Vaccination can also have other benefits, such as reducing the burden on the health care system, saving costs associated with treating and managing diseases, improving the quality of life and productivity of individuals and society, and contributing to global health security and equity. Vaccination can also prevent or eradicate some diseases that have no effective treatment or cure, such as polio, measles, and smallpox. By preventing these diseases, vaccination can also prevent the emergence of new variants or strains of pathogens that may be more virulent or resistant to existing treatments or vaccines.
Vaccination is one of the most effective and safe public health interventions that has saved millions of lives and prevented countless disabilities and sufferings. According to the World Health Organization (WHO), vaccination prevents 2-3 million deaths every year from diseases such as diphtheria, tetanus, pertussis (whooping cough), influenza, and measles. It is estimated that an additional 1.5 million deaths could be avoided if global vaccination coverage improves. The WHO also declared that vaccination is a human right and a shared responsibility that requires collective action and solidarity among all stakeholders. Therefore, the purpose of vaccination is not only to protect oneself, but also to protect others and contribute to a healthier and safer world.
Active immunization can prevent a wide range of infections caused by bacteria, viruses, fungi and parasites. Some of these infections are:
- Hepatitis A: This is a viral infection that affects the liver and can cause fever, jaundice, nausea and abdominal pain. Hepatitis A vaccine is given as two doses, six months apart, to children aged one year and older and to adults who are at risk of exposure. The vaccine provides protection for up to 20 years.
- Influenza: This is a viral infection that affects the respiratory system and can cause fever, cough, sore throat, muscle aches and fatigue. Influenza vaccine is given annually to people aged six months and older, especially those who have chronic medical conditions, are pregnant or are over 65 years old. The vaccine protects against the strains of influenza virus that are expected to circulate in a given season.
- Measles: This is a viral infection that affects the skin and respiratory system and can cause fever, rash, cough, runny nose and conjunctivitis. Measles vaccine is given as part of the measles-mumps-rubella (MMR) vaccine to children aged 12 to 15 months and again at four to six years old. The vaccine provides lifelong protection in most cases.
- Mumps: This is a viral infection that affects the salivary glands and can cause fever, swelling of the cheeks and jaw, headache and loss of appetite. Mumps vaccine is given as part of the MMR vaccine to children aged 12 to 15 months and again at four to six years old. The vaccine provides lifelong protection in most cases.
- Rubella: This is a viral infection that affects the skin and lymph nodes and can cause fever, rash, swollen glands and joint pain. Rubella vaccine is given as part of the MMR vaccine to children aged 12 to 15 months and again at four to six years old. The vaccine provides lifelong protection in most cases. Rubella infection during pregnancy can cause serious birth defects in the fetus, so women of childbearing age should be vaccinated before conception.
- Yellow fever: This is a viral infection that affects the liver and kidneys and can cause fever, jaundice, bleeding and organ failure. Yellow fever vaccine is given as a single dose to people aged nine months and older who are traveling to or living in areas where yellow fever is endemic or epidemic. The vaccine provides protection for at least 10 years.
- Polio: This is a viral infection that affects the nervous system and can cause paralysis, muscle weakness and respiratory failure. Polio vaccine is given as either an oral polio vaccine (OPV) or an inactivated polio vaccine (IPV) to children aged two months to six years old. The OPV contains live attenuated polio virus and is given as drops in the mouth. The IPV contains killed polio virus and is given as an injection. Both vaccines provide lifelong protection in most cases.
- Tetanus: This is a bacterial infection that affects the nervous system and can cause muscle spasms, lockjaw and breathing difficulties. Tetanus vaccine is given as part of the diphtheria-tetanus-pertussis (DTP) vaccine to children aged two months to six years old and as part of the tetanus-diphtheria (Td) or tetanus-diphtheria-acellular pertussis (Tdap) vaccine to adolescents and adults. The vaccine provides protection for up to 10 years.
- Diphtheria: This is a bacterial infection that affects the throat and respiratory system and can cause sore throat, fever, swollen glands and breathing difficulties. Diphtheria vaccine is given as part of the DTP or Td/Tdap vaccines to children aged two months to six years old and adolescents and adults. The vaccine provides protection for up to 10 years.
- Pertussis: This is a bacterial infection that affects the respiratory system and can cause severe coughing spells, whooping sound, vomiting and breathing difficulties. Pertussis vaccine is given as part of the DTP or Tdap vaccines to children aged two months to six years old and adolescents and adults. The vaccine provides protection for up to five years.
- Haemophilus influenzae type b (Hib): This is a bacterial infection that affects the respiratory system and can cause meningitis, pneumonia, septicemia and epiglottitis. Hib vaccine is given as part of the DTP-Hib or Hib-HepB vaccines to children aged two months to five years old. The vaccine provides protection for up to five years.
- Hepatitis B: This is a viral infection that affects the liver and can cause jaundice, cirrhosis
Active immunization has several advantages over passive immunization, which involves transferring antibodies from an immune individual to a non-immune one. Some of the benefits of active immunization are:
- Long-lasting protection: Active immunization stimulates the production of memory cells that can recognize and respond to the same antigen in the future. This means that the immune system can mount a faster and stronger response upon re-exposure to the pathogen, preventing or reducing the severity of the disease. The duration of immunity varies depending on the type and dose of the vaccine, but it can last for years or even a lifetime in some cases. Passive immunization, on the other hand, only provides temporary protection that wanes as the transferred antibodies are degraded or eliminated from the body.
- Reactivation potential: Active immunization can be reactivated by a natural infection or a booster dose of the vaccine, which can enhance the level and quality of the immune response. This can help maintain immunity against pathogens that mutate or evade the immune system over time. Passive immunization does not have this advantage, as it does not induce memory cells or stimulate the immune system to produce its own antibodies.
- Cost-effectiveness: Active immunization is generally cheaper and easier to produce and administer than passive immunization, which requires harvesting antibodies from human or animal sources. Active immunization also reduces the need for repeated doses of passive immunization, which can be expensive and inconvenient. Additionally, active immunization can prevent or reduce the burden of infectious diseases, which can save health care costs and improve quality of life.
Active immunization has some limitations and disadvantages that should be considered before choosing it as a preventive measure. Some of the drawbacks of active immunization are:
- Delayed protection: Active immunization requires the stimulation of the immune system to produce antibodies and memory cells, which takes time to develop. Depending on the type and dose of the vaccine, it may take several days to weeks for the protective response to be established. This makes active immunization ineffective as a post-exposure remedy, as it may not prevent the infection or reduce its severity in time. For example, the rabies vaccine requires multiple doses over several weeks to confer immunity, which may not be sufficient to prevent the fatal disease if administered after exposure to the virus.
- Individual variability: Active immunization depends on the individual`s immune response, which may vary depending on various factors such as age, health status, genetic background, and previous exposure to the antigen. Some individuals may not respond adequately to the vaccine, resulting in low or no protection. Others may have adverse reactions to the vaccine, such as allergic reactions, inflammation, fever, or pain at the injection site. These reactions may be mild or severe, and may require medical attention or discontinuation of the vaccination. For example, some people may have anaphylaxis or Guillain-Barré syndrome after receiving certain vaccines, which can be life-threatening.
- Logistical challenges: Active immunization requires careful planning and coordination to ensure that the vaccine is available, accessible, affordable, and acceptable to the target population. This involves maintaining a cold chain for storage and transportation of the vaccine, ensuring adequate supply and distribution of the vaccine, training and supervising health workers to administer the vaccine safely and correctly, monitoring and evaluating the coverage and effectiveness of the vaccination program, and addressing any barriers or misconceptions that may hinder the acceptance of the vaccine. These challenges may be more pronounced in resource-limited settings or during outbreaks or emergencies.
- Ethical issues: Active immunization may raise some ethical questions regarding the safety, efficacy, necessity, and equity of the vaccine. Some people may have concerns about the potential risks or side effects of the vaccine, especially if it is new or experimental. Others may question the need or benefit of the vaccine, especially if they perceive the disease as mild or rare. Still others may object to the vaccine on religious, cultural, or personal grounds, or demand their right to refuse or consent to the vaccination. Additionally, some people may face inequities in accessing or affording the vaccine due to social or economic factors.
These drawbacks do not outweigh the benefits of active immunization in most cases, but they should be taken into account when designing and implementing vaccination programs. By addressing these challenges and respecting the rights and preferences of individuals and communities, active immunization can be a safe and effective way to prevent infectious diseases and improve public health.
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