Vaccine safety and effectiveness - Frequently asked questions
Why are vaccines are important?
- Vaccines are the most effective way to prevent infectious diseases.
- Vaccines save lives. After clean water, vaccination is the most effective public health intervention in the world.
- Vaccination is the most important thing we can do to protect ourselves and our children against ill health. Vaccines prevent up to 3 million deaths worldwide every year.
- Vaccines are the only way to eradicate disease. We have eradicated smallpox and are near to eradicating polio, both through using vaccines.
- Measles vaccination alone has prevented 20 million measles cases and 4,500 deaths in the UK.
- Vaccines teach your immune system how to create antibodies that protect you from diseases. It's much safer for your immune system to learn this through vaccination than by catching the diseases and treating them. Once a vaccine has trained your immune system to know how to fight a disease, it can often protect you for many years.
- Neither HIV nor malaria have vaccines, which shows just how challenging the process of developing a vaccine can be.
How do vaccines work?
To create a vaccine for a disease, the germ which causes it is weakened, or completely inactivated so that it cannot cause the disease in question. When this weakened or ‘dead’ germ is introduced to the immune system, it trains the immune system to recognise the disease and fight it off if you come into contact with it in the future.
Are vaccines safe?
Vaccines are now safer than ever before. Any vaccine must first go through the usual rigorous testing and development process and be shown to strict standards of safety, quality and effectiveness before it can be used.
Are the vaccines safe for people with pre-existing health conditions?
The trials have involved people with chronic underlying conditions deliberately, and they have involved people from very broad age ranges and quite a lot of people in older age groups. The Joint Committee on Vaccination and Immunisation (JCVI) has looked at this, there’s no indication that there should be any difficulty in vaccinating people with chronic underlying conditions.
The JCVI has prioritised people, not just by age, but also 18 to 65 year olds with certain conditions because they are at high risk from coronavirus compared with the general population. The main risk groups identified by the committee are set out below:
- chronic respiratory disease, including chronic obstructive pulmonary disease (COPD), cystic fibrosis and severe asthma
- chronic heart disease (and vascular disease)
- chronic kidney disease
- chronic liver disease
- chronic neurological disease including epilepsy
- Down’s syndrome
- severe and profound learning disability
- solid organ, bone marrow and stem cell transplant recipients
- people with specific cancers
- immunosuppression due to disease or treatment
- asplenia and splenic dysfunction
- morbid obesity
- severe mental illness