Types of Vaccines
Vaccines can be divided into two main types.
1. Live attenuated vaccines
- Contain whole bacteria or viruses which have been “weakened”.
- Create a strong and lasting immune response
- Do not cause the disease in healthy people but not suitable for people with a weakened immune system as the bacteria or virus can multiply too much and cause the disease
2. Inactivated vaccines
- Contain whole bacteria or viruses which have been killed / or small parts of bacteria or viruses, such as proteins or sugars
- Don’t always create as strong or long-lasting immune response as live vaccines.
- Usually needs repeated doses and/or booster doses.
- Adjuvants often added to help strengthen and lengthen the immune response.
- Cannot cause disease even in people with a weakened immune system
A. ‘Whole killed’ vaccines - These vaccines contain whole killed bacteria or virus – There are currently no ‘whole killed bacteria’ vaccines used in the UK.
B. Subunit vaccines - Most vaccines in the UK NHS schedule are subunit vaccines. They don’t contain whole bacteria or viruses. They contain only polysaccharides (sugars) or proteins from surface of the bacteria or viruses. These polysaccharides or proteins are recognised as foreign antigens by the immune system.
- There are different types of subunit vaccines :
- Toxoid vaccine - Some bacteria release toxins when they infect the body. The immune system recognises these as foreign antigens, Vaccines can be made with inactivated toxins to trigger a string immune response
- Conjugate vaccines - In most conjugate vaccines, the polysaccharide (sugar) is attached to a toxoid protein (see ‘Toxoid vaccines’ above). Helping to generate a stronger immune response to the polysaccharide alone.
- Recombinant vaccines - A small piece of DNA is taken from the virus or bacteria for which the vaccine will protect against. The DNA fragment is inserted into other bacterial or yeast cell. These cells then produce large quantities of antigen - usually just a single protein or sugar. These are purified and used as the active ingredient in the vaccine.
For more information on the types of vaccines and which are currently within the NHS vaccination schedule or travel vaccinations