A vaccine is a lab-made biological preparation that is given to healthy children or people to give them immunity to particular diseases.
Vaccines themselves are harmless and don't give people the disease they are designed to protect against, for example the flu vaccine won't give you flu. Vaccines can be made up of the following:
- parts of the germs
- killed or weakened (attenuated) germs that can't cause disease
- germs that are closely related to human ones, but which don't cause disease in people
They often contain other molecules that give the vaccine an extra boost and makes it more powerful (called adjuvant).
Vaccines can protect people against many germs, including bacteria, viruses, and parasites. They can be given as injections, a nasal spray or a drop of liquid for people to swallow.
Vaccines work by triggering an immune reaction to a harmless form of the germs. The immune system learns from the encounter and remembers it, so next time it encounters the same germ it can swiftly destroy it before the germ multiples and causes sickness.
But just like us, the immune system's memory can fade over time, which is why you might need a booster to top up immunity every now and then.
Here's a video by the Oxford Vaccine Group that explains more.
- Vaccination already prevents an estimated 2 to 3 million deaths every year. But we could do better - if more people could access or took up the offer of vaccination, an additional 1.5 million deaths could be avoided.
- Around 19.5 million babies worldwide are missing out on basic vaccines, putting them at risk of preventable illness.
- It normally takes more than 10 years to develop a vaccine.
- Vaccines are incredibly cost-effective; they cost less than treating disease, and by saving lives and improving health they boost peoples' education and work prospects, improving the overall economy of a country.
If you want to find out more, you might be interested in reading this guide from the British Society of Immunology about childhood immunisations.