Vaccines and immunization: What is vaccination?

Thursday 21 October, 2021

What is vaccination?

Vaccination is a simple, safe, and effective way of protecting you against harmful diseases, before you come into contact with them. It uses your body’s natural defenses to build resistance to specific infections and makes your immune system stronger.

Vaccines train your immune system to create antibodies, just as it does when it’s exposed to a disease. However, because vaccines contain only killed or weakened forms of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complications.

How does a vaccine work?

Vaccines reduce risks of getting a disease by working with your body’s natural defenses to build protection. When you get a vaccine, your immune system responds. It:

  • Recognizes the invading germ, such as the virus or bacteria.
  • Produces antibodies. Antibodies are proteins produced naturally by the immune system to fight disease.
  • Remembers the disease and how to fight it. If you are then exposed to the germ in the future, your immune system can quickly destroy it before you become unwell.

The vaccine is therefore a safe and clever way to produce an immune response in the body, without causing illness.

Our immune systems are designed to remember. Once exposed to one or more doses of a vaccine, we typically remain protected against a disease for years, decades or even a lifetime. This is what makes vaccines so effective. Rather than treating a disease after it occurs, vaccines prevent us in the first instance from getting sick.

When should I get vaccinated (or vaccinate my child)?

Vaccines protect us throughout life and at different ages, from birth to childhood, as teenagers and into old age. In most countries you will be given a vaccination card that tells you what vaccines you or your child have had and when the next vaccines or booster doses are due. It is important to make sure that all these vaccines are up to date.

If we delay vaccination, we are at risk of getting seriously sick. If we wait until we think we may be exposed to a serious illness – like during a disease outbreak – there may not be enough time for the vaccine to work and to receive all the recommended doses.

If you have missed any recommended vaccinations for you or your child, talk to your healthcare worker about catching up.

What diseases do vaccines prevent?

Vaccines protect against many different diseases, including:

  • Cervical cancer
  • Cholera
  • COVID-19
  • Diphtheria
  • Ebola virus disease
  • Hepatitis B
  • Influenza
  • Japanese encephalitis
  • Measles
  • Meningitis
  • Mumps
  • Pertussis
  • Pneumonia
  • Polio
  • Rabies
  • Rotavirus
  • Rubella
  • Tetanus
  • Typhoid
  • Varicella
  • Yellow fever

Some other vaccines are currently under development or being piloted, including those that protect against Zika virus or malaria, but are not yet widely available globally.

Not all of these vaccinations may be needed in your country. Some may only be given prior to travel, in areas of risk, or to people in high-risk occupations. Talk to your healthcare worker to find out what vaccinations are needed for you and your family.

Who can get vaccinated?

Nearly everyone can get vaccinated. However, because of some medical conditions, some people should not get certain vaccines, or should wait before getting them. These conditions can include:

  • Chronic illnesses or treatments (like chemotherapy) that affect the immune system;
  • Severe and life-threatening allergies to vaccine ingredients, which are very rare;
  • If you have severe illness and a high fever on the day of vaccination.

These factors often vary for each vaccine. If you’re not sure if you or your child should get a particular vaccine, talk to your health worker. They can help you make an informed choice about vaccination for you or your child.

What is in a vaccine?

All the ingredients of a vaccine play an important role in ensuring a vaccine is safe and effective. Some of these include:

  • The antigen. This is a killed or weakened form of a virus or bacteria, which trains our bodies to recognize and fight the disease if we encounter it in the future.
  • Adjuvants, which help to boost our immune response. This means they help vaccines to work better.
  • Preservatives, which ensure a vaccine stays effective.
  • Stabilisers, which protect the vaccine during storage and transportation.

Vaccine ingredients can look unfamiliar when they are listed on a label. However, many of the components used in vaccines occur naturally in the body, in the environment, and in the foods we eat. All of the ingredients in vaccines – as well as the vaccines themselves – are thoroughly tested and monitored to ensure they are safe.

Are vaccines safe?

Vaccination is safe and side effects from a vaccine are usually minor and temporary, such as a sore arm or mild fever. More serious side effects are possible, but extremely rare.

Any licensed vaccine is rigorously tested across multiple phases of trials before it is approved for use, and regularly reassessed once it is introduced. Scientists are also constantly monitoring information from several sources for any sign that a vaccine may cause health risks.

Remember, you are far more likely to be seriously injured by a vaccine-preventable disease than by a vaccine. For example, tetanus can cause extreme pain, muscle spasms (lockjaw) and blood clots, measles can cause encephalitis (an infection of the brain) and blindness. Many vaccine-preventable diseases can even result in death. The benefits of vaccination greatly outweigh the risks, and many more illnesses and deaths would occur without vaccines.

Are there side effects from vaccines?

Like any medicine, vaccines can cause mild side effects, such as a low-grade fever, or pain or redness at the injection site. Mild reactions go away within a few days on their own.

Severe or long-lasting side effects are extremely rare. Vaccines are continually monitored for safety, to detect rare adverse events.

Is there a link between vaccines and autism?

There is  no evidence of any link between vaccines and autism or autistic disorders. This has been demonstrated in many studies, conducted across very large populations.

The 1998 study which raised concerns about a possible link between measles-mumps-rubella (MMR) vaccine and autism was later found to be seriously flawed and fraudulent. The paper was subsequently retracted by the journal that published it, and the doctor that published it lost his medical license. Unfortunately, its publication created fear that led to dropping immunization rates in some countries, and subsequent outbreaks of these diseases.

We must all ensure we are taking steps to share only credible, scientific information on vaccines, and the diseases they prevent.(source World Health Organisation)

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