Vaccine Efficacy
We learnt about active and passive immunity in a previous section and will be expanding on those ideas here.
Booster Doses
Passive immunity can be achieved quickly but doesn't offer long lasting protection. Injecting human immunoglobulins can be used before a vaccine has time to create an immune response. e.g. in the event of exposure to a disease. Antibody levels in the blood are temporarily raised, created short lasting immunity. This means that booster doses are needed in order to maintain this level of immunity.
Active immunity can also need booster doses. These are designed to increase both the level of the immune response and the time the immunity lasts for. The time period between the primary and secondary doses are vaccine-specific.
WARNING - Live vaccines should be deferred for 3 months after receiving any blood products. This is because the normal human immunoglobulin found in blood products could reduce the immune response. For further advice see The Green Book.
Vaccine Efficacy
Vaccines are not 100% effective and do not produce a full immune response in every patient. They can fail in 2 ways:
- Primary failure - when someone fails to make an ummunological response to the vaccine.
- Secondary failure - when an individual initially responds but protection wanes over time. Whilst they may still become infected, they may experience milder forms of the disease and are less likely to suffer severe complications than an unvaccinated person.