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Dispelling Myths About how does a Vaccine Trial Work: Separating Fact from Fiction

how does a vaccine trial work

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Vaccines are among the most effective tools to prevent and control infectious diseases. However, many myths and misconceptions exist about how does a Vaccine Trial Work and how vaccines are developed and tested for safety and efficacy. This blog will separate fact from fiction by explaining vaccine trials\’ basic steps and principles.

What is a vaccine trial?

A vaccine trial is similar to clinical trials that aim to establish a vaccine\’s safety and efficacy before clinical researchers license it.  Identifying drugs through pre-clinical evaluation can be done through the candidate vaccine drug. The licensing includes screening and selecting antigens properly, invoking the immune response.

Some vaccine trials may take months or years, depending on the time required for the subjects to react to the vaccine and develop the required antibodies. This is how clinical research works are conducted following strict ethical and scientific standards. They are overseen by regulatory authorities such as the Food and Drug Administration of the U.S. (FDA) or WHO.

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What are the phases of vaccine trials?

Vaccine trials typically go through four phases before they are approved for widespread use:

Phase 1 

A few volunteers took vaccines (usually 20-100), and by taking vaccination, the clinical researchers assessed its safety to confirm it generates an immune response and determine its correct dosage. Vaccines are generally tested in young, healthy adult volunteers in this phase. 

Phase 2

The vaccine is given to more significant volunteers (usually hundreds) to evaluate its safety and immunogenicity further and identify any common side effects. This phase may include different populations, such as older adults or people with chronic conditions.

Phase 3 

The vaccine is given to an extensive group of volunteers (usually thousands or tens of thousands) to measure its efficacy and safety in preventing the disease under natural conditions. This phase involves a randomized controlled trial on how does a Vaccine Trial Work, where some participants receive the vaccine, and others receive a placebo or another vaccine. The participants and the researchers do not know who received what until the end of the trial. This phase also monitors for any rare or severe adverse events that may occur after vaccination.

Phase 4

The vaccine is approved for use and monitored for its long-term safety and effectiveness in the general population. This phase involves how do vaccine trials work and additional studies to evaluate the vaccine\’s impact on specific groups, such as pregnant women or children, or to compare it with other vaccines. 

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What are some common myths and facts about vaccine trials?

Myth 1: Vaccines contain many harmful ingredients


Fact 1

Different vaccines contain various ingredients allowing safe product administration. Clinical researchers may find that any substance is harmful with its high doses, even water. However, vaccines contain only tiny amounts of ingredients well below the levels that can cause harm. Some of these ingredients include:


These substances enhance the immune response to the vaccine antigen. They help reduce the amount of antigen needed per dose, lowering the cost and increasing the vaccine supply. Examples of adjuvants include aluminium salts, oil-in-water emulsions, or saponins.


Preservatives prevent microbial vaccine contamination during their use and storage. They help ensure the safety and quality of vaccines, and this is how do clinical trials work. Examples of preservatives include thimerosal (a mercury-containing compound), phenol, or 2-phenoxyethanol.


These substances protect vaccines from temperature, light, or acidity changes. They help maintain the potency and effectiveness of vaccines. Examples of stabilizers include sugars (such as sucrose or lactose), amino acids (such as glycine or alanine), and proteins (such as gelatin or albumin).

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Myth 2: Testing for the COVID-19 vaccine wasn\’t diverse.


Fact 2

Trials began with small groups before expanding to more significant numbers (tens of thousands), including a wide range of people. Clinical trials included people of different ages, races, sexes, and health conditions, including HIV, diabetes, and lung disease. For example, according to Pfizer/BioNTech\’s data submitted to the FDA for emergency use authorization, their phase 3 trial involved 43,448 participants from six countries (United States of America, Argentina, Brazil, South Africa, Germany, and Turkey), of whom 42% were from diverse ethnic backgrounds. 

Similarly, according to Moderna’s data submitted to the FDA for emergency use authorization, phase 3 is on how clinical trials work involving 30,420 participants from the United States, of whom 37% were from diverse ethnic backgrounds. These trials also included people with underlying medical conditions that put them at higher risk of severe COVID-19.

Diversity within how does a Vaccine Trial Work for a COVID-19 vaccine helps ensure safety and effectiveness across populations. It may increase confidence in getting the vaccine among people of colour who have been disproportionately affected by the pandemic. However, there are still challenges and barriers to achieving adequate representation of ethnic minorities in vaccine trials, such as lack of trust, access, awareness, and engagement. Therefore, more efforts are needed to address these issues and promote equity and inclusion in vaccine research and delivery.

Myth 3: The vaccines are unsafe because they were developed so fast. 


Fact 3

Scientists developed the COVID-19 vaccines faster than any other vaccine — in under 1 year. In the 1960s, the previous record was for four years with the mumps vaccine. However, this does not mean that the vaccines are unsafe or that any shortcuts were taken. However, there are multiple reasons why the COVID-19 vaccines developed so quickly:


      • Unprecedented global collaboration and coordination among scientists, governments, regulators, and funders to share resources, data, and expertise.

      • The availability of existing platforms and technologies that could be adapted for the new coronavirus. For example, mRNA vaccines have been studied for decades for diseases such as influenza, Zika, and rabies. 

      • The accelerated regulatory processes allowed for simultaneous testing and evaluation of vaccine candidates without compromising safety or quality standards. 

      • The large-scale enrollment and participation of volunteers in vaccine trials willing to contribute to the fight against the pandemic.

    All the approved vaccines of COVID-19 WHO for emergency use listing have been through randomized clinical trials to test their quality, safety, and efficacy. Vaccines must have a high efficacy rate of 50% or above to be approved. After approval, they continue to be monitored for ongoing safety and effectiveness in the general population.

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    Vaccine trials are essential for ensuring that vaccines are safe and effective before being used publicly. However, many myths and misconceptions exist about how does a Vaccine Trial Work, how vaccine trials work, and what they entail. In this blog, we have tried to dispel some of these myths by explaining the basic steps and principles of vaccine trials, focusing on COVID-19 vaccines. We hope this blog has helped you understand more about vaccine trials and why they matter for public health.

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