Vaccines are one of the most important discoveries of humankind, saving millions of lives every year. In simple words, vaccines work by stimulating the immune system to fight against specific diseases. The immunity generated by the vaccine keeps the disease from affecting someone in the future. In this article, we will learn in detail about the science behind vaccines and immunity.
What is immunity?
Immunity is the body’s capability to protect itself from the onslaught of harmful viruses, bacteria, and other infectious agents. It is the body’s defense mechanism that eliminates the pathogen before it can cause damage.
The types of immunity
The immune system recognizes and attacks the pathogen with the help of two types of immunity:
- Innate immunity
- Adaptive immunity
The innate immunity is the primary response of the body to a pathogen, and it is not specific to any particular microbe. It involves the activation of white blood cells, which engulf the pathogen and destroy it. The adaptive immunity, on the other hand, is specific to the pathogen and involves the production of a specific type of protein, called an antibody, that recognizes and binds to the pathogen, making it easy for the white blood cells to identify and destroy it.
How do vaccines work?
Vaccines are made of either weakened or dead pathogens or parts of the pathogen that cannot cause the disease, but still provoke an immune response. The vaccine tricks the immune system into believing that the body has been infected with the pathogen, and thus, it produces antibodies against the pathogen. The next time the body encounters the same pathogen, it responds quickly and effectively, eliminating the pathogen before it can cause any damage.
The process of immunity through vaccination
The body’s response to vaccination involves three stages:
- Primary response
- Memory response
- Effector response
The primary response occurs when the body is exposed to a pathogen for the first time. The body identifies the pathogen and produces specific antibodies to fight against it. The memory response is the consequence of the primary response when the body ‘remembers’ the pathogen that it had encountered. The effector response is the rapid activation of the memory response that eliminates the pathogen.
Types of vaccines
There are several types of vaccines used to stimulate the immune response in the body. The following are the most common types of vaccines:
Inactivated vaccines are made by killing the pathogen with heat or chemicals. The dead pathogen cannot cause disease, but still stimulate an immune response in the body.
Live attenuated vaccines
Live attenuated vaccines involve using a weakened form of the pathogen. The live pathogen cannot reproduce or cause disease, but still provokes an immune response in the body. This type of vaccine is more effective than inactivated vaccines because it mimics a natural infection.
Subunit, recombinant, or conjugate vaccines
Subunit, recombinant, or conjugate vaccines use only parts of the pathogen, rather than the entire pathogen, to stimulate an immune response. These vaccines are often safer and better-tolerated than other types.
Viral vector vaccines
Viral vector vaccines are created by modifying a virus to express a part of the pathogen. The immune system responds to the viral vector, recognizing the pathogen if encountered in the future.
Why are vaccines important?
Vaccines are essential for controlling and preventing infectious diseases. Vaccines provide long-lasting immunity, often for a lifetime. Vaccines protect those who cannot be vaccinated, such as infants and those who are immunocompromised. Vaccination also helps in preventing outbreaks of infectious diseases.
Herd immunity is the indirect protection from an infectious disease that occurs when a large percentage of the population becomes immune to the disease. The immunity of the vaccinated individuals breaks the chain of transmission of the infectious agent, leading to a significantly reduced number of infections, with the unvaccinated individuals also benefitting from the reduced disease transmission. For herd immunity to be effective, a sufficient percentage of the population needs to be vaccinated.
What is vaccine hesitancy?
Vaccine hesitancy is the reluctance or refusal to vaccinate despite the availability of vaccines. It is a significant barrier to the global control and elimination of many infectious diseases. Vaccine hesitancy may arise from various reasons, such as religious beliefs, mistrust of vaccine manufacturers or the government, side effects of the vaccine, and more. It is essential to address the concerns of vaccine-hesitant individuals and provide them with accurate and reliable information to influence their decision to vaccinate.
Debunking vaccine myths
There are several myths surrounding vaccines that contribute to vaccine hesitancy. Here are some of the most prevalent myths:
- Myth: Vaccines cause autism
- Myth: Vaccines contain harmful ingredients
- Myth: Vaccine-preventable diseases are no longer a threat
- Myth: Natural immunity is better than vaccine-induced immunity
These are all myths. Research has shown that vaccines are safe and effective, and the risks associated with vaccine-preventable diseases outweigh the risks associated with vaccines.
Vaccines have transformed the face of global public health. They are among the most cost-effective and successful health interventions ever discovered. They protect individuals, communities, and populations from deadly infectious diseases, and are an essential tool in controlling and eliminating diseases. Vaccination is the best way to keep oneself and the community safe from infectious diseases.
 Cunha, B. A. (2019). Vaccinations. Medscape. https://emedicine.medscape.com/article/217231-overview
 Immunization basics. (2021). Centers for Disease Control and Prevention.https://www.cdc.gov/vaccines/basics/index.html
 Vaccine development, testing, and regulation. (2019). U.S. Food and Drug Administration. https://www.fda.gov/vaccines-blood-biologics/development-approval-process-cber/vaccine-development-testing-and-regulation
Here are some common questions and answers related to the topic of why do vaccines work:
- Q: Are vaccines safe?
A: Yes. Vaccines are carefully tested before being approved for use. The risks associated with vaccine-preventable diseases outweigh the risks associated with vaccines themselves. Serious adverse effects are rare.
- Q: How long does vaccine-induced immunity last?
A: The longevity of vaccine-induced immunity varies by vaccine. Some vaccines provide lifelong immunity, while others require booster doses to maintain protection.
- Q: What are common side effects of vaccines?
A: Common side effects of vaccines include pain and swelling at the injection site, fever, headache, and fatigue. Severe allergic reactions are rare.
- Q: Do vaccines cause autism?
A: No. Several studies have shown that vaccines do not cause autism.
- Q: What is herd immunity?
A: Herd immunity is the indirect protection from an infectious disease that occurs when a large percentage of the population becomes immune to the disease. The immunity of the vaccinated individuals breaks the chain of transmission of the infectious agent, leading to a significantly reduced number of infections.