What do vaccines do?

Vaccination helps a person’s immune defences to overcome a common disease that they may be exposed to. Being vaccinated prevents people from catching the disease in the vast majority of cases.

In some cases, a person can still get a disease after being vaccinated, but the symptoms are milder and recovery is faster.

Some of the diseases that vaccines protect against are

  • hepatitis B
  • human papillomavirus infection (HPV)
  • influenza
  • measles, mumps and rubella
  • polio
  • tetanus
  • tuberculosis

Better for everyone

A vaccinated person is less likely to pass on an infectious disease to others, so vaccination can help protect those who cannot be vaccinated themselves. This includes

  • babies
  • children
  • older people
  • people with weak immune systems such as cancer patients

These groups benefit from others getting vaccinated, because the disease cannot then spread in the community.

A high number of vaccinations is required to help create this community immunity. When a high number of people are vaccinated, chains of infections are stopped. For example, according to the European Centre for Disease Prevention and Control (ECDC) 95% of people need to vaccinate against measles to prevent further spread in the community.  

Reducing the burden on people

By helping keep more people healthy, vaccination helps reduce the social and psychological toll of illness on people and lessens the burden on hospitals and healthcare systems. This means that resources can go to fighting other diseases, such as cancer or Alzheimer’s.

How do COVID-19 vaccines work?

Vaccines work by preparing a person's immune system (the body’s natural defences) to recognise and defend itself against a specific disease.

Building immunity

Most research on COVID-19 vaccines involves generating responses to all or part of a protein that is unique to the virus that causes COVID-19. When a person receives the vaccine, it will trigger an immune response. Most COVID-19 vaccines require two doses to build immunity.

If the person is infected by the virus later on, the immune system recognises the virus. The system is then prepared to attack the virus.

Vaccines bought by the European Commission

Nucleic (mRNA) Acid vaccines

  • BioNTech/Pfizer
  • Moderna
  • CureVac

This type of vaccine contains part of the ‘instructions’ from the virus that causes COVID-19. This allows the body’s own cells to make a protein that is unique to the virus.

The person’s immune system recognises that this unique protein should not be in the body and responds by producing natural defences against infection by COVID-19.

mRNA technology explained

Protein-based vaccines

  • Sanofi/GSK
  • Novavax

This type of vaccine contains fragments of a protein that is unique to the virus.

These are enough for the person’s immune system to recognise that the unique protein should not be in the body and responds by producing natural defences against infection by COVID-19.

Viral vector vaccines

  • AstraZeneca
  • Johnson & Johnson

This type of vaccine uses a different, harmless virus to deliver the ‘instructions’ from the virus that causes COVID-19.

This allows the body’s own cells to make the protein unique to the COVID-19 virus.

The person’s immune system recognises that this unique protein should not be in the body and responds by producing natural defences against infection by COVID-19.

Inactivated virus vaccine

  • Valneva

Valneva is a European biotechnology company developing an inactivated virus vaccine, made of the live virus through chemical inactivation.

This is a traditional vaccine technology, used for 60-70 years, with established methods and a high level of safety.

Most of the flu vaccines and many childhood vaccines use this technology.

More information on COVID-19 vaccination

For more information about the vaccination programme in your country, see the ECDC vaccine scheduler and visit the official websites on vaccination of the countries of the European Union and the European Economic Area.

Vaccine success stories

Smallpox

Thanks to vaccination, smallpox has been completely wiped out. It was once a common disease that killed a third of people who contracted it. The last case of naturally contracted smallpox was in 1977 and it was eradicated in 1980.

 

Polio

Polio is an infectious disease mostly contracted by children. One person in 200 develops incurable paralysis after infection. A vaccine was developed in 1955 and widely introduced. As of 2020, the only remaining cases of polio have been found in Pakistan and Afghanistan.  

 

Measles

The measles virus was identified in 1954 and a vaccine was introduced in 1963. Thanks to vaccination, between 2000 and 2018, global deaths from measles fell by 73%. 23 million deaths were prevented. The Americas have been measles-free since 2002. However, outbreaks of measles still occur in several European countries because vaccination coverage is insufficient in certain areas.

 

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