Vaccines, Vaccination and Immunisation: Definition, Overview, Types, Examples

Vaccination is a process of stimulating the body’s immune system to develop protection against specific infectious diseases. It works by introducing a harmless form of the disease-causing organism, prompting the immune system to respond. This response creates memory cells that help the body fight future infections. One important concept related to this is antigens, which trigger the immune response during vaccination.

This Story also Contains

1. What are Vaccines?
2. Types of Vaccines
3. Mechanism of Action
4. Vaccination Process
5. How Vaccination Works?
6. What is Immunisation?
7. History and Development of Vaccines
8. Importance of Vaccines and Immunisation
9. Common Vaccines and Their Uses
10. Vaccine Safety and Side Effects
11. Challenges and Future of Vaccination
12. MCQs on Vaccination
13. Recommended Video on Vaccination & Immunisation

Vaccines play a crucial role in public health by preventing the spread of deadly diseases and reducing outbreaks. They are a major part of immunology and contribute to the body's defense through the production of antibodies. It is important to understand how vaccines work to grasp how our immune system protects us from viral diseases, bacterial infections, and other serious health conditions.

What are Vaccines?

Vaccines are remarkable biological preparations that help our bodies develop some kind of immunity against specific diseases. They perform it by stimulating antibody production. In simple words, vaccines mimic infectious agents, thereby giving our bodies easier recognition and elimination of them.

Types of Vaccines

Vaccines are developed using different methods to stimulate the body’s immune response. Each type is designed to provide protection against specific diseases. They help the immune system recognize and fight pathogens effectively. The different types of vaccines are described below:

Live-attenuated vaccines

They contain live pathogens, but in a form so weakened that they can replicate within our bodies without giving rise to full-blown diseases. Examples are MMR (measles, mumps, rubella), and varicella chickenpox vaccines. They elicit strong and long-lasting immunity.

Inactivated vaccines

In these vaccines, the disease-causing pathogens are either dead or unable to perform cell division. Sometimes, multiple doses are required to fully develop the necessary immunity. The polio vaccine (IPV) and the hepatitis A vaccine are examples of inactivated vaccines.

Subunit vaccines:

The makers of these vaccines only use certain parts of the germ, such as proteins or sugars, so that they can stimulate immunity. They minimise the likelihood of side effects by giving much attention to key antigens. The hepatitis B vaccine and the human papillomavirus (HPV) vaccine are a few examples.

Toxoid vaccines:

These are formed from inactivated poisons made by the agent. Instead of the agent itself, the toxin decides to conquer. Instances such as diphtheria and tetanus vaccines are in this category.

mRNA vaccines:

This implies that the cell will now produce particular proteins, which are components of the pathogen, upon the use of messenger ribonucleic acid, or mRNA, hence calling for an immune response just in case such things happen. mRNA remains in the body for a short time as compared to the period after which synthesis has occurred. An example includes the COVID-19 vaccinations created by Pfizer-BioNTech and Moderna.

Vector-based vaccines:

A virus (not responsible for the disease) is used in these instances to introduce genetic data that tell cells to make proteins that trigger the body’s defence system. The virus that serves as a delivery mechanism is benign. One instance would be the Ebola vaccine and the COVID-19 vaccine from Johnson & Johnson.

Mechanism of Action

Vaccines work by triggering the immune system to recognize and respond to disease-causing organisms. This helps the body build memory against future infections. The process involves the activation of immune cells and the production of antibodies. Vaccines can activate our bodies’ natural defences, thus enabling them to recognise specific disease germs.

Primary Immune Response

In administering a vaccine, you inject antigens (parts of the pathogen) into the body. Thereafter, the immune system recognises these antigens as foreign and starts the primary immune response with them. The role of various immune cells like macrophages, dendritic cells and B cells during this phase is to process and present the antigens to T cells. As a result of this interplay, B cells are activated so that they may produce antibodies while memory cells form.

Memory Cells

The primary response by the immune system results in memory B cells and T cells, which stay in the body for quite a while once generated due to their capacity for recognition of antigens.

Secondary Immune Response

Memory cells are called into play if our body ever meets the real deal again. This allows our immune system to turn on a much quicker and stronger response called the secondary immune response.

Vaccination Process

Vaccination involves administering a vaccine to an individual, usually through injection. It follows a specific schedule based on age and health needs. The process ensures that the immune system is trained and ready. Regular immunization helps in controlling and eliminating infectious diseases. Vaccination is the practice of introducing a vaccine into the body to create immunity against certain infections.

How Vaccination Works?

Depending on the vaccine type and the disease to be awarded against, vaccines can be given by injection, by oral drops, or even by nasal sprays. The job of the vaccine is to present antigens to the body, harmless parts of a pathogen, so that our immune system will learn to recognize them and be ready to attack.

Technology has advanced to the point where immunisation can be done effectively in very simple steps. A good reason why we need to do this is because it helps protect us from many serious infections that cause diseases.

What is Immunisation?

Simply put, immunisation is shielding an individual from a disease with a vaccine that triggers an immune response, developing immunity. Therefore, this is important for lowering the spread of communicable diseases and keeping people healthy

Natural vs. Acquired Immunisation

Natural Immunisation:

This is a situation where an individual gets immune to a specific disease when he contacts it naturally. During the presence of a pathogen, for example, microbes or viruses, inside our bodies, the immune system is activated, leading to an attack against it. If such an attack is victorious, then one does not suffer from any similar diseases afterwards, due to the resistance developed by one’s whole system from that particular sickness outbreak.

Acquired Immunisation:

When someone receives a vaccine and is vaccinated, they become immune to a disease, which is what we call acquired immunisation. Vaccines can contain the pathogen's whole live attenuated dead attenuated or specific antigens, e.g., proteins, sugar. Therefore, subsequent vaccination of the same person with a weakened form is necessary. Oother infections could occur at this point, so the strength of the antigens needs enhancement through subsequent vaccinations.

History and Development of Vaccines

Centuries have passed since the first attempts at vaccination when cowpox was transmitted to the public as a way of making them immune to smallpox. Nonetheless, there were grave dangers associated with this technique.

Edward Jenner's Smallpox Vaccine:

In 1796, the first effective smallpox vaccine was developed by the English physician Edward Jenner. This happened in England, which had a greater population density than any other place; therefore, it was easier for one person to infect another. He found out that when people get infected with cowpox, they do not contract smallpox, which is more lethal. This was observed by Edward Jenner, who was an English physician at the time. He tested it out by inoculating an eight-year-old boy with pus from a cowpox pustule and later exposing him to pus from a smallpox pustule. As a result, the boy did not suffer from smallpox. This discovery marked the initiation of vaccines.

Modern Vaccine Development

Process:

Modern vaccine development is active in all these stages: research, clinical performances, regulatory review, and mass production. Scientists first identify the pathogen-causing disease and then develop vaccines that invoke the immune system to recognise and fight pathogens.

Clinical Trials:

During Phase I, some patients volunteer simply as a way of ensuring that they are indeed safe before taking the right dose. When it comes to drugs like vaccines, they go through both preclinical and clinical trials before finally undergoing human trials aimed at testing them. It is carried out to make sure they are safe and effective. Meanwhile, Phase II encompasses large-scale experimental designs intending to determine efficacy and monitor harmful reactions.

Regulatory Bodies:

Agencies such as the World Health Organisation (WHO) are instrumental in the approval and surveillance of vaccines. This is done via research data analysis for safety and efficacy standards at the general population level before approval can be granted for their use.

Importance of Vaccines and Immunisation

Vaccines play a crucial role in preventing the spread of infectious diseases. They help protect individuals by building immunity and the immune system. Immunisation has significantly reduced the prevalence of deadly diseases. It is a key component of public health programs worldwide.

Reduction in Disease:

Many infectious diseases have been prevented or mitigated greatly by vaccines, leading to less suffering because the use of vaccines has increased everywhere. For example, thanks to vaccination for smallpox, it was possible to eradicate this disease in the 1980s making it one of the greatest successes of public healthcare ever. Polio, measles, and diphtheria are also some other diseases whose incidence has reduced considerably through vaccination whilst many deaths and disabilities have been avoided.

Mortality Rates:

Vaccinations have led to a substantial fall in worldwide death rates, especially among children, due to our ability to prevent these fatal diseases. Immunisation initiatives have averted serious illnesses affecting defenceless members, such as newborns or old people, besides patients on immune-suppressing drugs.

Economic Benefits: Cost-Effectiveness

Preventing diseases saves money on medication, hospitalisation, and long-term care because vaccines stop diseases. Also, the cost to society of disease prevention via vaccination is reduced through decreased absenteeism and lost productivity.

Economic Burden

Vaccines prevent diseases with significant economic impacts, including healthcare costs and lost productivity in terms of economic development, and this is a very good way to reduce healthcare expenditure and promote economic prosperity.

Social and Ethical Considerations:

Requiring immunisation raises key societal and ethical concerns, particularly concerning compulsory vaccine programs and personal freedoms. To safeguard the well-being of society as well as attain “herd immunity,". Notwithstanding their contentious nature sometimes, these laws serve to avert epidemics and stop sickness among people who cannot get vaccinated because of other medical reasons like allergies or pregnancy.

Common Vaccines and Their Uses

Several vaccines are routinely given to protect against diseases. These vaccines are part of the national immunisation schedule. They are important for children, adults, and high-risk groups. Their use has led to the control and near-eradication of many infections.

Childhood Vaccines

MMR (Measles, Mumps, and rubella):

The MMR vaccine is used to prevent measles, mumps, and rubella, which are all highly infectious viral diseases. It is usually given twice in childhood and has played a significant role in decreasing its occurrence.

DTaP (Diphtheria, Tetanus, Pertussis):

The vaccine DTaP helps protect against diphtheria, tetanus or pertussis (childhood whooping cough). It is administered as a series of shots that begin in infancy and go into the early years of childhood, with additional doses as booster shots recommended later on.

Polio Vaccine:

There are two forms of the polio vaccine, which include, inactivated poliovirus and oral poliovirus. In both cases, these forms protect people from the virus that causes it; it is known as poliovirus and can lead to paralysis., At present, global immunisation campaigns have put an end to polio.

Hepatitis B Vaccine:

This remedy guards against the hepatitis B virus, a condition whereby the liver remains infected over a long period and eventually causes either cancer or collapse. It starts from birth, one usually gets it in between three and four dosages.

Adult Vaccines

Influenza (Flu) Vaccine:

To shield adults against the seasonal influenza virus, it is advised that they be vaccinated every year, also known as the flu vaccine. This reduces the chances of flu-related complications, which are more dangerous among elderly people along with individuals with chronic unhealthy conditions such as asthma or diabetes.

Shingles (Herpes Zoster) Vaccine:

Adults over fifty years of age are advised to take immunisation against shingles, a painful skin rash that results from reactivation of the chicken pox virus. This vaccination also lessens the chances of getting chronic nerve pains that are related to this disease.

HPV (Human Papillomavirus) Vaccine:

The vaccine is used to protect people against the virus, which leads to cancer of the cervix as well as genital warts and some other cancers, though less common ones. It is recommended that those who are yet to be teens get inoculated, but adults up to 26 and, at times, even older age groups should take it.

Special Vaccines

Travel Vaccines:

Individuals require travel vaccines when they travel to areas with common diseases. An instance would be the yellow fever vaccine which is a must-have in parts of Africa and South America. Such travel vaccines are against typhoid, cholera, and Japanese encephalitis.

Vaccines for Immunocompromised Individuals:

Individuals with immunodeficiency, such as cancer patients during chemotherapy or individuals living with HIV/AIDS might need individualised vaccination timetables. These are extra doses or specific vaccines required to provide full immunity. For example, an individual could be given pneumococcal vaccination to prevent pneumonia and other types of pneumococcal infections.

Vaccine Safety and Side Effects

Vaccines go through rigorous testing before approval to ensure safety. Most side effects are mild, like fever or soreness at the injection site. Serious reactions are rare and monitored closely. Overall, the benefits of vaccination outweigh the risks.

Safety Monitoring

We rigorously monitor the safety of the vaccine by using a combination of protocols covering both pre- and post-licensure phases. Before they are approved for use, vaccines must pass through very intensive clinical trials aimed at determining how safe and efficient they are. By doing so, such systems are instrumental in ensuring the continued safety of vaccines and immediate action if need be.

Common Side Effects

Side effects induced by most vaccines are usually mild and short-lived. They may include the following symptoms: Pain, redness or swelling at the place where an injection was given generally disappears within a few days. A mild fever can be experienced when one’s immune system is reacting to the vaccine. The other common side effect is fatigue or mild malaise, which disappears within a few days without any medication.

Rare Adverse Events

Although vaccines are mostly safe, they can sometimes cause severe but uncommon adverse effects. For example, these are very uncommon reactions and usually happen in about 1 out of every million doses of the vaccine. Severe allergic reactions (anaphylaxis). However, prompt medical attention can help control these reactions if they occur.

Challenges and Future of Vaccination

Despite success, challenges like vaccine hesitancy, misinformation, and access issues remain. New diseases and virus mutations demand continuous research. Future vaccines aim to be more effective and easier to distribute. Innovations like mRNA vaccines show promising potential.

Global Vaccination Coverage

In developed versus developing countries, vaccination coverage differs, which is one of the major problems facing global health. Robust healthcare systems and ready vaccine availability have traditionally ensured high levels of vaccination in rich countries. But poorer communities face logistical constraints, inadequate infrastructure and limited healthcare services, resulting in lower vaccination rates.

Emerging Challenges

In the same way, antibiotics can become ineffective against bacteria strains due to resistance development, some infectious agents may grow up being able to withstand vaccines. Although it may occur rarely, these occurrences have serious implications for the efficacy of immunisation programmes all over the world. There are also practical challenges like the need for cold chain facilities during the storage and transit of vaccines which are hard to transport into these places because they are too far off from civilization.

Innovations in Vaccinology

• The COVID-19 vaccines that rely on mRNA technology are a major milestone in vaccine development. Unlike traditional vaccines, mRNA vaccines are easier to make and can be quickly produced in response to new disease outbreaks.
• Improvements in genetic modification along with improvements in immunology have opened up avenues for the customisation of vaccines depending on an individual’s genetics, thus leading to potentially more efficient vaccinations with fewer ill effects.
• Programs such as COVAX are aimed at making sure that all regions can access the vaccines fairly regardless of their economic status.

MCQs on Vaccination

Q1. Read the following statements and select the correct ones.

i) Vaccine is a preparation (or suspension) of a dead/attenuated pathogen of a disease which on inoculation(or injection) into a healthy person, provides temporary/permanent active/passive immunity by inducing antibody formation.

ii) Immunisation is the process by which the body produces antibodies against vaccine-preventable diseases through the administration of specific vaccines.

iii) The principle of immunization or vaccination is based on the property of 'memory' of the immune system.

iv) If a person is infected with some deadly microbes to which a quick immune response is required; in that case, we need to directly inject the preformed antibodies or antitoxins e.g., in case of tetanus.

1. (i) and (ii)

2. (iii) and (iv)

3. (i), (ii) and (iii)

4. (i), (ii), (iii) and (iv)

Correct answer: 4) (i), (ii), (iii) and (iv)

Explanation:

Vaccination involves introducing a preparation into the body that contains antigenic proteins of a pathogen, or inactivated/weakened forms of the pathogen, known as a vaccine. This stimulates the immune system to produce a defensive response which includes the generation of memory cells, without causing the actual disease.

Hence, the correct answer is option 4) (i), (ii), (iii) and (iv).

Q2. Passive immunization includes:

1. Introduction of antibodies directly

2. Transfer of maternal antibodies across placenta

3. Transfer of lymphocytes directly

4. All of these

Correct answer: 4) All of these

Explanation:

Prepared antibodies, antitoxins, or antivenoms are injected for immediate protection against diseases. It is very useful in emergencies, such as after exposure to toxins or infectious agents. For example, tetanus exposure can be treated with tetanus immunoglobulin, and snake bites can be treated with antivenom. It gives rapid immunity but does not induce long-lasting immune memory; hence, it is a temporary measure for immediate health threats.

Hence the correct answer is Option 4) All of these.

Q3. The principle of vaccination is based on the property of

1. Specificity

2. Diversity

3. Memory

4. Discrimination between ‘self’ and ‘non-self’

Correct answer: 3) Memory

Explanation:

A vaccine is a biological preparation that provides active acquired immunity against infectious disease. It is prepared from the killed form or weakened microbe, its surface protein, or its toxin. The agent is used to stimulate the immune system of the body to identify the agent as a threat and destroy it and develop a memory for further recognition and destruction of any microorganism that is associated with the same agent which may be encountered in the future. So, a vaccine contains an agent resembling a disease-causing microbe.

Hence the correct answer is Option 3) Memory.

Also Read:

• MCQs on Vaccination

• Plasmodium Life Cycle

• Human Health and Disease

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