How Vaccines Work: A Detailed Exploration

Corresponding Author:

Negile Wandour
Department of Biotechnology,
University of Baraawe,
Baraawe,
Somalia
E-mail: Wandourfethoor@gmail.com

Received: 27-Sep-2024, Manuscript No. ACTVR-24-148934; Editor assigned: 02-Oct-2024, Pre QC No. ACTVR-24-148934 (PQ); Reviewed: 16-Oct-2024, QC No. ACTVR-24-148934; Revised: 21-Oct-2024, Manuscript No. ACTVR-24-148934 (R); Published: 28-Oct-2024, DOI: 10.37532/ ACTVR.2024.14(5).270-271

Introduction

Vaccines represent one of the greatest public health achievements in human history, credited with saving millions of lives by preventing serious and deadly diseases. From smallpox to polio, measles to COVID-19, vaccines have played a crucial role in controlling or eradicating many infectious diseases. But how do vaccines work, and what is the science behind them? This article will delve into the mechanisms that drive vaccine efficacy, their development process, and how they stimulate the immune system to offer protection.

Description

Understanding the immune system

Before delving into generational differences, it is essential to understand the immune system. The immune system can be broadly categorized into two types: Innate immunity and adaptive immunity.

Innate immunity: Refers to the body’s first line of defense. It is non-specific and reacts quickly to potential threats. This includes barriers like the skin, enzymes in saliva, and immune cells such as macrophages and neutrophils.

Adaptive immunity: This is a more specialized and targeted response. It involves lymphocytes (B and T cells), which recognize and respond to specific pathogens. Adaptive immunity has a key feature-memory. Once the immune system has fought off a pathogen, it “remembers” it and is prepared to respond more quickly if the pathogen is encountered again in the future.

The role of vaccines in adaptive immunity

Vaccines work by leveraging the concept of immune memory. Essentially, a vaccine trains the immune system to recognize and combat specific pathogens without causing the disease itself. Here’s how this process typically unfolds:

Exposure to antigens: Vaccines contain antigens, which are molecules that mimic parts of a virus or bacteria (such as proteins or polysaccharides). These antigens are not harmful by themselves but are enough to trigger an immune response. In some cases, vaccines contain weakened or inactivated forms of the virus (attenuated vaccines), while in others, they only contain fragments (like protein subunits or mRNA).

Activation of immune response: Once the vaccine is administered, the immune system detects the foreign antigens and mounts a response. B cells (a type of lymphocyte) are activated, producing antibodies that are specific to the pathogen in question. Meanwhile, T cells help coordinate the immune response, killing infected cells and supporting B cells in producing antibodies.

Formation of memory cells: After the initial response, the immune system creates memory B and T cells. These cells remain in the body, often for many years or even a lifetime, ready to recognize and combat the pathogen if it is encountered again. This is why people who are vaccinated are much less likely to contract the disease, and if they do, the illness is often milder.

Types of vaccines

Vaccines come in several forms, depending on how the antigens are presented to the immune system. These various approaches have different advantages and disadvantages, but they all aim to achieve the same result—an effective immune response.

Live attenuated vaccines: These vaccines use a weakened form of the pathogen that can’t cause disease in healthy people. Examples include the Measles, Mumps, and Rubella (MMR) vaccine and the oral polio vaccine. These tend to provide long-lasting immunity but are not suitable for individuals with weakened immune systems.

Inactivated vaccines: These contain pathogens that have been killed or inactivated. The immune system still recognizes the dead pathogens and mounts a response. An example is the Inactivated Polio Vaccine (IPV) or the hepatitis A vaccine. These vaccines often require multiple doses to maintain immunity.

Subunit, recombinant, polysaccharide, and conjugate vaccines: These vaccines use specific pieces of the pathogen-such as its protein, sugar, or capsid (a casing around the pathogen). Because these vaccines only contain parts of the pathogen, they are safer and can be given to people with weakened immune systems. Examples include the HPV and hepatitis B vaccines.

mRNA vaccines: A newer approach, mRNA vaccines (such as the Pfizer and Moderna COVID-19 vaccines) use a snippet of the pathogen’s genetic material (mRNA). This mRNA instructs cells to produce a protein similar to one found on the virus. The immune system then learns to recognize this protein and creates antibodies against it.

Viral vector vaccines: These vaccines use a modified version of a different virus (not the one causing the disease) to deliver instructions to cells. The cells produce a protein that triggers the immune response. The AstraZeneca COVID-19 vaccine is an example of this type of vaccine.

Preclinical studies: Before a vaccine is tested in humans, it undergoes laboratory research, often using animal models.

Phase 1 trials: A small group of healthy volunteers is given the vaccine to assess its safety, dosage, and side effects.

Phase 2 trials: The vaccine is tested on a larger group to further assess safety and immune response.

Phase 3 trials: Thousands of people are enrolled in these trials to determine the vaccine’s effectiveness in preventing the disease and to monitor for rare side effects.

Approval and post-market surveillance: Even after a vaccine is approved, it is continuously monitored for safety through systems like the Vaccine Adverse Event Reporting System (VAERS) in the U.S.

How vaccines provide herd immunity

One of the most important benefits of widespread vaccination is herd immunity. Herd immunity occurs when a large portion of the population becomes immune to a disease, either through vaccination or previous infection, reducing the overall spread of the disease. When herd immunity is achieved, even individuals who are not vaccinated (such as those who cannot be vaccinated due to medical reasons) are protected because the pathogen cannot spread easily.

For herd immunity to be effective, a certain percentage of the population must be vaccinated. This threshold varies depending on the disease; for example, measles requires about 95% of the population to be vaccinated, while for polio, about 80% coverage is sufficient.

Conclusion

Vaccines work by stimulating the immune system to recognize and combat pathogens, providing long-term protection without causing the diseases themselves. They have revolutionized modern medicine and continue to be one of the most effective ways to prevent infectious diseases. From live attenuated vaccines to the cuttingedge mRNA vaccines, the science behind them continues to evolve, offering hope in the fight against both old and emerging diseases.