How do vaccines work?

Editorial Team

Editorial Team

April 20th, 2021

Editorial Team

‘To understand how vaccines work, we need to understand the immune system’

Vaccines help to boost the natural immune system, protecting us from some of the viruses and bacteria that can cause diseases. Understanding the immune system is essential to understanding how they do this and how long immunity lasts.

A video by the Oxford Vaccine Group explains how the body’s immune system recognises ‘foreign invaders’ such as the measles virus or pertussis bacterium.

How long do vaccines protect for?
Depending on the vaccine, some (but not all) immunisations must be repeated. For example, children who have received both of their MMR injections are likely to benefit from protection against measles, mumps and rubella for life.

However, with polio, diphtheria, tetanus, or whooping cough, experts say the initial immunisation lasts for between five and 10 years.

The protection provided by the influenza vaccine is even shorter. This is because flu viruses may change from season to season, meaning that all vaccine-eligible individuals – including the more vulnerable older people, for example – must get a new vaccine every year. Boosters can be described as a ‘reminder’ to your immune system.

It is not yet known how long immunity from COVID-19 vaccines will last: nobody has had COVID-19 – nor the COVID-19 vaccine – for much longer than a year. Over time, it will become clear whether booster vaccines would be necessary to maintain protection.

There are some signs that people who had SARS (which is a coronavirus) in 2003 still show some immunity. This may give reason to hope that natural and vaccine-induced immunity against COVID-19 will be long-lasting. Time will tell.

For information on some of the scientific terms mentioned in the video above, check out our glossary.

How are vaccines developed?

By studying the immune system, scientists have developed vaccines that prepare the body to protect itself against viruses and bacteria. New vaccines are rigorously tested before they are recommended by independent experts.

Find out how vaccines are tested to ensure they are safe and effective in this short animation.