Pastel Pathways

Vaccines are arguably one of the biggest but quietest triumphs of modern medicine. A small injection, often single dose, lasting barely seconds, can protect us against a myriad of diseases that once shaped entire chapters of human history.

It has been known for ages that the best way to prevent the spread of communicable diseases, is by herd immunity. What this means is that when a significant percentage of the population becomes immune to an infectious disease, the spread is reduced and vulnerable individuals may be protected. It is also known as population immunity.

One of the ways to achieve herd immunity is by vaccination. From small pox eradication to COVID-19 vaccine development, vaccination has transformed public health in ways that is often overlooked today. So how exactly do vaccines work? And why are they considered one of the most powerful tools in preventive medicine?

Let’s take a closer look. 🌿

What is a Vaccine? 💉

Vaccine is a prophylactic or preventive medication that helps the immune system learn how to recognise and fight a pathogen, like viruses or bacteria, without causing the disease itself.

Think of it like a training session for your immune system. Instead of encountering the dangerous infection, your body gets a safe preview of the pathogen that allows the immune system time to prepare itself and tighten its defences in advance.

Once vaccinated, the immune system can respond faster, because it has already recognised the pathogen due to the vaccine and can help in preventing or reducing the severity of an infection.

How the immune system learns 🦠

When a vaccine enters the body, it introduces molecules called the antigen, pieces of virus or bacteria that the immune system recognises as foreign. This triggers several immune responses:

1. Antibody Production: Special immune cells called B-cells produce proteins called antibodies which can bind to the pathogen and neutralise it.

2. Activation of Immune cells: T cells help co-ordinate immune response and destroy infected cells, if needed.

3. Immune memory: Perhaps the most important step, the body stores information about the pathogen through memory B and T-cells, allowing for rapid response in the future. This immune memory can last years, sometimes a lifetime and is why many infections like chicken pox, mostly only happen once in a lifetime.

Types of vaccines

COVID-19 Vaccine: A new era of vaccine technology

The recent COVID-19 pandemic marked a turning point in vaccine development. Unlike traditional vaccines, mRNA vaccines were used and their rapid development showed how quickly science can respond to global health challenges.

Unlike other types of vaccines, mRNA vaccines do not contain the virus or bacteria itself but contain the necessary instructions that allow our cells to form a harmless piece of the virus (like a spike protein) that teaches the immune system to recognise and respond if exposed to it later.

While long-term effects of this vaccine are still being studied, the rapid development of this vaccine was made possible due to the feat of modern biotechnology. It showed that global collaboration can accelerate medical breakthroughs and the mRNA vaccines provide a new technology that is currently being studied for other diseases.

HPV Vaccine: Preventing cancer before it starts

The Human Papilloma Virus Vaccine or the HPV vaccine has shown remarkable success is not only preventing infection but also reducing the rate of incidence of some forms of cancers.

HPV is a very common virus that can spread through close contact. While many strains of this virus cause infections that can clear naturally, some more high-risk strains can cause cancers like cervical cancer, oropharyngeal (throat) cancer, penile cancer, anal cancer.

Currently recommended for women and girls aged 9-45, this vaccine has been found to lower invasive cervical cancer incidence by up to 87% and has shown a 97% reduction in the rate of pre-cancerous lesions. While all initial campaigns are focused on vaccinating women due to its focus on cervical cancer, the vaccine is also approved for men to prevent HPV infection, penile cancer and forms of cancers that can affect both sexes like anal and oropharyngeal cancers.

Since this vaccine is found to be more effective prior to exposure to the virus, public health campaigns are focusing on vaccination 9-14 year old children, and might eventually grow in scale to include other populations. The HPV vaccine was the first of its kind to be designed specifically to kill a cancer-causing virus (the only exception being Hepatitis B vaccine, which can protect against liver cancer, but is not its primary purpose).

Some common vaccine misconceptions

1. Vaccines can give you the disease they protect against: Most vaccines cannot cause the disease they protect since they use either a deactivated or weakened form of the pathogen or just small pieces of the virus or bacterium. While these components are enough to trigger an immune response, they cannot cause an infection. Some vaccines may cause mild symptoms of soreness, fever or fatigue which are signs that the immune system is learning and responding to the pathogen.
2. Natural Immunity is better than Vaccine Immunity: While it is true that recovering from certain infections can produce immunity, it often comes with severe health risks, including long-term complications, sepsis and death. Vaccines can cause protection without exposing the body to the dangers of the disease.
3. Vaccines cause autism: This claim, quite possibly the most common misconception related to vaccines, arises from a paper published in 1998 which was retracted for fraudulent data and ethical violations, as published in editorials and news articles since (https://www.bmj.com/content/342/bmj.c7452.full). Since this study, several large scale studies have been conducted, involving thousands of children and have found no evidence linking vaccines to autism.
4. Vaccines contain harmful ingredients: Vaccines contain carefully tested ingredients which ensure stability, effectiveness and safety. These include preservatives, stabilisers, and tiny amounts of adjuvants which mimic danger signals that can help activation of immune responses. All ingredients of vaccines undergo rigorous testing for stability, safety and undergo regulatory review before approval. Vaccines are also continuously monitored once they are in the market and any adverse effects are noted by both the company and the regulatory authorities.

Conclusion: Protection through prevention

Vaccines are a beautiful example of how science can work with the body by teaching our immune system how to respond to danger before it even arrives, turning prevention into one of medicine’s most powerful forms of care.

From childhood immunisations to newer vaccine innovations like COVID-19 vaccines and cancer-preventing HPV vaccines, these seemingly small interventions continue to shape healthier futures for individuals and communities alike.

While conversations around vaccines can sometimes feel overwhelming, the science behind them remain simple and involve the same basic principles of preparation, prevention and progress. Each vaccine represents years of research, global collaboration efforts, and a shared goal of reduced suffering.

Here at Pastel Pathways, it is a reminder that some of the most powerful advances of biomedical science can come in forms that may sometimes be no bigger than a single drop in a syringe. ✨

References

1. Center for Disease Control and Prevention (CDC). How Vaccines work. https://www.cdc.gov/vaccines/basics/explaining-how-vaccines-work.html
2. World Health Organization (WHO). Vaccines and Immunization: What is Vaccination? https://www.who.int/news-room/questions-and-answers/item/vaccines-and-immunization-what-is-vaccination
3. Exploring natural components in vaccine delivery systems: Types, routes of administration, in-vitro and in-vivo quantification techniques. https://www.sciencedirect.com/science/article/pii/S1773224725003636
4. UK Health Security Agency (UKHSA). What are mRNA vaccines and how do they work? https://ukhsa.blog.gov.uk/2024/03/11/what-are-mrna-vaccines-and-how-do-they-work/
5. National Center for Immunization and Respiratory Diseases (U.S.). Division of Viral Diseases. Understanding mRNA COVID-19 vaccines. https://stacks.cdc.gov/view/cdc/119428
6. Center for Disease Control and Prevention (CDC). HPV Vaccination. https://www.cdc.gov/hpv/vaccines/index.html
7. World Health Organization (WHO). WHO statement on autism-related issues. https://www.who.int/news/item/24-09-2025-who-statement-on-autism-related-issues
8. Deer B. How the case against the MMR vaccine was fixed BMJ 2011; 342 :c5347 https://www.bmj.com/content/342/bmj.c5347.full