What is vaccination?
Vaccination is a simple, safe, and effective way of protecting people against harmful diseases before they come into contact with them. It uses your body’s natural defenses to build resistance to specific infections and makes your immune system stronger.
Vaccines train your immune system to create antibodies, just as it does when it’s exposed to a disease. However, because vaccines contain only killed or weakened forms of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complications.
Most vaccines are given by an injection, but some are given orally (by mouth) or sprayed into the nose.
Why is vaccination important?
Vaccination is a safe and effective way to prevent disease and save lives – now more than ever. Today there are vaccines available to protect against at least 20 diseases, such as diphtheria, tetanus, pertussis, influenza and measles. Together, these vaccines save the lives of up to 3 million people every year.
When we get vaccinated, we aren’t just protecting ourselves, but also those around us. Some people, like those who are seriously ill, are advised not to get certain vaccines – so they depend on the rest of us to get vaccinated and help reduce the spread of disease.
During the COVID-19 pandemic, vaccination continues to be critically important. The pandemic has caused a decline in the number of children receiving routine immunizations, which could lead to an increase in illness and death from preventable diseases. WHO has urged countries to ensure that essential immunization and health services continue, despite the challenges posed by COVID-19.
How does a vaccine work?
Vaccines reduce risks of getting a disease by working with your body’s natural defenses to build protection. When you get a vaccine, your immune system responds. It:
Recognizes the invading germ, such as the virus or bacteria.
Produces antibodies. Antibodies are proteins produced naturally by the immune system to fight disease.
Remembers the disease and how to fight it. If you are then exposed to the germ in the future, your immune system can quickly destroy it before you become unwell.
The vaccine is therefore a safe and clever way to produce an immune response in the body, without causing illness.
Our immune systems are designed to remember. Once exposed to one or more doses of a vaccine, we typically remain protected against a disease for years, decades or even a lifetime. This is what makes vaccines so effective. Rather than treating a disease after it occurs, vaccines prevent us in the first instance from getting sick.
How do vaccines protect individuals and communities?
Vaccines work by training and preparing the body’s natural defences – the immune system – to recognize and fight off viruses and bacteria. If the body is exposed to those disease-causing pathogens later, it will be ready to destroy them quickly – which prevents illness.
When a person gets vaccinated against a disease, their risk of infection is also reduced – so they’re also far less likely to transmit the disease to others. As more people in a community get vaccinated, fewer people remain vulnerable, and there is less possibility for passing the pathogen on from person to person. Lowering the possibility for a pathogen to circulate in the community protects those who cannot be vaccinated due to other serious health conditions from the disease targeted by the vaccine. This is called “herd immunity.”
“Herd immunity” exists when a high percentage of the population is vaccinated, making it difficult for infectious diseases to spread, because there are not many people who can be infected. But herd immunity only works if most people are vaccinated. At the same time, herd immunity does not protect against all vaccine-preventable diseases. For example, tetanus is caught from bacteria in the environment, not from other people, so those who are unimmunized are not protected from the disease even if most of the rest of the community is vaccinated.
Why should I get vaccinated?
Without vaccines, we are at risk of serious illness and disability from diseases like measles, meningitis, pneumonia, tetanus and polio. Many of these diseases can be life-threatening. WHO estimates that vaccines save between 2 and 3 million lives every year.
Although some diseases may have become uncommon, the germs that cause them continue to circulate in some or all parts of the world. In today’s world, infectious diseases can easily cross borders, and infect anyone who is not protected.
Two key reasons to get vaccinated are to protect ourselves and to protect those around us. Because not everyone can be vaccinated – including very young babies, those who are seriously ill or have certain allergies – they depend on others being vaccinated to ensure they are also safe from vaccine-preventable diseases.
Vaccines protect against many different diseases, including:
Cervical cancer, Cholera, Diphtheria, Hepatitis B, Influenza, Japanese encephalitis, Measles, Meningitis, Mumps, Pertussis, Pneumonia, Polio, Rabies, Rotavirus, Rubella, Tetanus, Typhoid, Varicella, Yellow fever etc
Some other vaccines are currently under development or being piloted, including those that protect against Ebola or malaria, but are not yet widely available globally.
Not all of these vaccinations may be needed in your country. Some may only be given prior to travel, in areas of risk, or to people in high-risk occupations. Talk to your healthcare worker to find out what vaccinations are needed for you and your family.
The general stages of the development cycle of a vaccine are:
Exploratory stage
Pre-clinical stage
Clinical development
Regulatory review and approval
Manufacturing
Quality control
> Clinical development is a three-phase process. During Phase I, small groups of people receive the trial vaccine. In Phase II, the clinical study is expanded and vaccine is given to people who have characteristics (such as age and physical health) similar to those for whom the new vaccine is intended. In Phase III, the vaccine is given to thousands of people and tested for efficacy and safety.
Many vaccines undergo Phase IV formal, ongoing studies after the vaccine is approved and licensed.
Stage 1 R&D
The process which takes anything between 2 to 4 years has been very quick in the case of Coronavirus. The reason for quick breakthrough in this stage was the fact that the Chinese government had shared the genetic sequence of the virus in January itself when the virus was within the confines of mainland China only. Also most vaccine candidates are not based on the protein of the vitus but its genetic sequence.
Stage 2: Pre Clinical
After the conclusion of the Research and Development, the vaccine is tested on animals and plants to analyse their efficacy and functioning. The scientists check whether the vaccine is inducing an immune response in the animal or plant body. If the answer is negative then the development turns back to stage 1 again which elongates the process.
Stage 3: Clinical trials
This is the most critical and significant stage in the development of vaccines as its efficacy is tested on humans. Out of the large number of candidates who succeed in reaching stage 2 fail to enter stage 3. This stage alone has the potential to take up to 90 months or close to over 7 years. This stage has 3 sub-stages or phases involved.
a) Phase 1: The vaccine is administered to a small group of people and they are tested to check whether antibodies have developed inside their bodies or not. This can take upto 3 months.
b) Phase 2: The number of people who are given the vaccine is enlarged to several hundreds and it may take upto 6-8 months on an average. The subjects are analysed to ascertain whether they develop the immune response against the disease. The ability of the vaccine to produce common and adverse reactions among the subjects called reactogenicity is also analysed. This stage has been shortened in the case of Coronavirus as several candidates which were in phase 2 some days back have now reached clinical trials phase 3.
c) Phase 3: Thousands of people are administered the vaccine and an attempt is made to see how the vaccine works in larger populations. This can again take another 6-8 months.
Stage 4: Regulatory review
After having succeeded in various stages and phases of human trials, the vaccine candidate seeks regulatory backing before embarking on the manufacturing of the vaccine. It usually takes a long time but in public emergencies like these, the time frame could be shortened.
Stage 5 : Manufacturing and Quality Control
This stage needs well oiled infrastructure of the vaccine producing company and financial resources to begin the process of manufacturing of the vaccine on a large scale.
Development of Vaccination
The most commonly used vaccines have been around for decades, with millions of people receiving them safely every year. As with all medicines, every vaccine must go through extensive and rigorous testing to ensure it is safe before it can be introduced in a country.
An experimental vaccine is first tested in animals to evaluate its safety and potential to prevent disease. It is then tested in human clinical trials, in three phases:
In phase I, the vaccine is given to a small number of volunteers to assess its safety, confirm it generates an immune response, and determine the right dosage.
In phase II, the vaccine is usually given hundreds of volunteers, who are closely monitored for any side effects, to further assess its ability to generate an immune response. In this phase, data are also collected whenever possible on disease outcomes, but usually not in large enough numbers to have a clear picture of the effect of the vaccine on disease. Participants in this phase have the same characteristics (such as age and sex) as the people for whom the vaccine is intended. In this phase, some volunteers receive the vaccine and others do not, which allows comparisons to be made and conclusions drawn about the vaccine.
In phase III, the vaccine is given to thousands of volunteers – some of whom receive the investigational vaccine, and some of whom do not, just like in phase II trials. Data from both groups is carefully compared to see if the vaccine is safe and effective against the disease it is designed to protect against.
Once the results of clinical trials are available, a series of steps is required, including reviews of efficacy, safety, and manufacturing for regulatory and public health policy approvals, before a vaccine may be introduced into a national immunization programme.
Following the introduction of a vaccine, close monitoring continues to detect any unexpected adverse side effects and further assess effectiveness in the routine use setting among even larger numbers of people to continue assessing how best to use the vaccine for the greatest protective impact.
Testing of vaccines
Once a promising vaccine is identified, it will firstly undergo scrupulous laboratory testing. This includes careful examination and testing of the vaccine and its ingredients. These tests evaluate the safety of the vaccine, and how well it prevents a disease.
If positive results are achieved in the lab, a manufacturer can then apply to do clinical trials. These trials typically involve several thousand healthy volunteers participants on a voluntary basis, whose safety is ensured by national regulatory authorities, and last for many years. The trials are bound by strict regulations and take place across three main phases:
During Phase I, small groups (approximately 20-50 people) receive the vaccine. This phase will assess the safety, side effects, appropriate dosage, method of administration and composition of the vaccine.
If it is successful, it will proceed to Phase II. At this stage, the vaccine is usually given to several hundred people. This group will have the same characteristics (e.g. age, sex) as the people for whom the vaccine is intended to be given.
In Phase III, the vaccine is usually given to thousands of people to help ensure it is safe and effective for broader use.
The results of all these studies will be assessed when regulators decide whether to approve a vaccine.
Studies may also take place after a vaccine is introduced. They enable scientists to monitor efficacy and safety among an even larger number of people, over a longer timeframe.
Vaccine Approval
In countries where vaccines are manufactured, national or regional regulators oversee a vaccine’s development. This includes approving clinical trials, evaluating their results, and taking decisions on licensing. In deciding, regulators must refer to very strict international standards on acceptable ethical clinical practice.
Once a vaccine has been developed, national regulators decide whether to introduce a vaccine in their countries. WHO provides information to support this process, through a comprehensive evaluation of the available evidence, and its regularly updated position papers on vaccines.
Read: AstraZeneca: COVID-19 vaccine provides up to 90% prevention
