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What is a Vaccine? How do Vaccines Work?


Lead Academy

9 Mins Read

Vaccinations are one of the greatest public health triumphs in history. They have saved countless lives and continue to protect us from a multitude of diseases. But what is a vaccine? How exactly do these remarkable inventions work?

Here’s the brief for you: Vaccines are like training wheels for your immune system, introducing a weakened germ or part of it to teach your body to fight it off later. You can prepare yourself for the real thing without getting sick this way.

In this blog, we’ll dive deep into the world of vaccines, exploring their definition, different types, and how they train our bodies to fight off disease. We’ll also debunk some common myths surrounding vaccination.

Nurse is administering vaccine to a young woman at a vaccination centre.

What is a Vaccine?

First, let’s define vaccines. A vaccine is a biological preparation that helps your body develop immunity to a particular disease. It contains a weakened or inactive form of a virus or bacteria or parts of it that trigger your immune system to learn how to fight the infection. When you later come into contact with the actual virus or bacteria, your body is already prepared to defend itself.

Vaccines are one of the most effective tools we have to prevent infectious diseases. They have helped to save millions of lives and control the spread of diseases such as measles, polio, and diphtheria.

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How Vaccines are Made

First, scientists grow the germ responsible for the disease, like a virus or bacterium, in a lab by infecting cells in a culture.

Then, they change the germ to make sure it doesn’t cause the disease itself. They do this by:

  • Weakening the germ by growing it many times until it’s less harmful. This is how MMR vaccines are made.
  • Using a part of the germ that triggers the immune system and putting it into the vaccine. The Hib vaccine is made this way.
  • Deactivating the toxin made by the germ. That’s how the tetanus vaccine is produced.

After treating the germ, scientists mix it with other stuff like stabilisers and preservatives to make a vaccine dose. This careful process ensures the vaccine helps the immune system fight the disease without making us sick.

3d illustration of vaccination passport with Syringe And Vaccine Bottle on blue background.

Types of Vaccines

Different kinds of vaccines exist, but they all do the same thing: help the immune system make antibodies. Here are some common types of vaccine shots:

Inactivated Vaccines:

  • These vaccines have a dead form of the germ that causes a disease.
  • You might need several doses over time for ongoing protection.
  • Examples: Hepatitis A, Flu, Polio, Rabies.

Live-Attenuated Vaccines:

  • These vaccines have a weakened form of the germ, causing the disease.
  • They create a strong and long-lasting immune response.
  • Some people with weak immune systems may need special precautions.
  • Examples: Measles, Mumps, Rubella (MMR), Rotavirus, Smallpox, Chickenpox, Yellow fever.

mRNA Vaccines:

  • These vaccines, like some COVID-19 vaccines, use mRNA to trigger an immune response.
  • They have benefits like faster manufacturing and no risk of causing the disease.
  • Example: COVID-19.

Subunit, Recombinant, Polysaccharide, and Conjugate Vaccines:

  • These vaccines use specific components of the germ, like proteins or sugars, to create a strong immune response.
  • They’re suitable for many people, including those with weak immune systems.
  • Extra vaccine doses might be needed for ongoing protection.
  • Examples: Hib disease, Hepatitis B, HPV, Whooping cough, etc.

Toxoid Vaccines:

  • These vaccines use a toxin from the germ, causing the disease.
  • They build immunity to the harmful parts of the germ, not the germ itself.
  • Extra vaccine doses might be needed for continuous protection.
  • Examples: Diphtheria, Tetanus.

Viral Vector Vaccines:

  • These vaccines use a changed version of another virus to provide protection.
  • Viruses like influenza, measles, or adenovirus (common cold virus) are used as carriers.
  • Examples: COVID-19 (some vaccines in trials).

Epidemiologist is conducting coronavirus research in a laboratory.

Importance of Vaccination

Vaccines are crucial for our health, preventing diseases like smallpox and polio. They’re especially important because if enough people don’t get vaccinated, these diseases can come back fast. The World Health Organisation says that vaccine hesitancy is a big problem for everyone’s health. For example, the prevalence of measles and mumps is coming back in England despite the MMR vaccine’s effectiveness.

To stop these diseases from spreading, it’s vital for at least 95% of kids to get vaccinated. As of February 1, 2024, a news report said more people were getting sick with norovirus and flu during winter, which was putting extra pressure on the NHS. This shows how crucial it is to get vaccinated for flu and COVID-19 to help reduce pressure on healthcare services.

Overall, routine vaccinations not only protect individuals but also benefit the entire community by creating a shield against diseases.

How do Vaccines Work?

Here, we’ll talk about vaccine and how it works:

  • Mimicking an Infection: Vaccines have a weakened or inactive germ or a part of it, called an antigen. When we get a vaccine, our immune system sees the antigen as a foreign invader and reacts to it.
  • Immune Response: Our white blood cells spot the antigen and make antibodies, which are special proteins made to fight that germ. These antibodies move around in our blood, ready to fight off the virus or bacteria if we come across it later.
  • Long-Term Protection: After our immune system makes antibodies and “learns” to fight the germ, it remembers what the virus or bacteria looks like. This gives us long-lasting immunity. So, if we meet the real virus or bacteria later, our immune system can quickly react and beat it before it makes us sick.

Newborn babies have some defence against diseases like measles, mumps, and rubella, passed from their moms through a special connection called the placenta. This protection lasts for a short time, maybe a few weeks or months. For measles, mumps, and rubella, it might last about a year. That’s why babies get the MMR shot when they turn one – to stay safe!

Close-up of 3d illustration of Coronavirus virus cell with COVID-19 vaccine and syringes..

Vaccine Myths Debunked: Setting the Record Straight

Vaccines are incredibly safe and effective. However, there’s a lot of misinformation surrounding them. Here are some common myths debunked:

  • Myth: Vaccines cause autism. Numerous scientific studies have thoroughly debunked this myth.
  • Myth: Vaccines weaken the immune system. Vaccination actually strengthens the immune system by training it to fight specific diseases.
  • Myth: I don’t need vaccinations because I’m healthy. Vaccines protect not only yourself but also those around you, especially those with compromised immune systems who cannot be vaccinated. These people belong to the herd community/ herd immunity group. So, immunisation and vaccination are essential for building immunity against infectious diseases.

Close-up of paediatrician giving vaccine to a little girl at the clinic.

Vaccine Safety

The MHRA closely monitors vaccines for any unusual side effects and to ensure they continue to work well, after thoroughly testing them for years before approving them for public use in the UK. Getting a shot may cause slight discomfort or soreness, but it is much better than getting seriously sick from preventable diseases.

Who Cannot Get Vaccines?

Not many people can’t get vaccines—it’s usually those who’ve had a severe allergic reaction before or are allergic to its ingredients. Also, if your immune system is weak, like during cancer treatment, some vaccines might not be safe for you.

If you’re unsure if you or your child can get vaccinated, ask your doctor, nurse, or pharmacist.

Side Effects of Vaccination

Most side effects of vaccines are mild and go away quickly. Common ones include a slight redness or swelling where the needle went in, feeling a bit unwell, or having a slight fever for a day or two. Some older kids or adults might feel a bit dizzy or tired and get a headache, mild fever, or flu-like symptoms.

And it’s okay if a child cries after a shot—that’s normal, and they’ll feel better with a little cuddle. Serious allergic reactions are very rare, and if these reactions happen, the person giving the shot knows how to handle the situation and will treat it right away. So, you or your child will recover well with quick treatment!

In addition, if you want to know can a healthcare assistant become a nurse? You should check out our informative blog.


1. How long do travel vaccinations last?

Travel vaccinations vary in duration: Regarding the Hepatitis A vaccine, you need a booster every 25 years; Typhoid lasts 3 years; Yellow fever vaccine provides lifelong protection; Dip/Tet and Polio may need boosters every 10 years for specific regions.

2. Who is eligible for the pneumonia vaccine on NHS?

The NHS offers the pneumonia vaccine to everyone over 65 and those aged 2 to 64 with specific health conditions. For most over 65, a single dose provides lifelong protection.

3. What did you expect from the vaccines?

Vaccines help our bodies make defences called antibodies, which protect us from certain diseases. This stops us from getting sick and helps stop germs from spreading to others.

4. What happens if a baby’s vaccination is delayed in the UK?

While delaying vaccination isn’t ideal, it’s best to contact your GP to reschedule. They can advise you on how to catch up on missed doses and ensure your baby receives full protection.

5. What happens if you get the COVID-19 vaccine while you are positive?

Getting the COVID-19 vaccine while positive may not be advisable as it could potentially exacerbate symptoms or cause complications. It’s recommended to wait until recovery to ensure its safety and effectiveness.

Wrapping Up

To sum it up, knowing about vaccines is really important to keep us healthy and our communities safe. Vaccines act like shields for our bodies, helping our immune system fight off dangerous diseases. They work by copying infections and giving us long-lasting protection. So, when someone asks, “What is a Vaccine?” remember, it’s not just a shot—it’s a strong tool against sickness.

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