Active immunity vs. Passive immunity! What’s the difference?
Active immunity is a result of exposure to a pathogen. Your body builds up an arsenal of neutralizing antibodies as well as b-cells and t-cells that allow for memory immunity. Exposure can occur either through true natural infection or through vaccination – both allow your body to mount an immune response that can react to future exposures.
Passive immunity, on the other hand, is short-term immunity that is acquired by antibodies introduced to your body, as opposed to being made by your own body. As a result, once the antibodies have been degraded (typically days to weeks) you will no longer have immunity. No b-cells or t-cells are produced with passive immunity – there is no memory. Antibody treatments (either monoclonoal antibodies or convalescent plasma) are examples of passive immunity. The antibodies in these cases are not self-produced and therefore do not result in your body building up other aspects of specific adaptive immunity. Maternal antibodies being passed to a baby (either in utero or through breastfeeding) are also examples of passive immunity.
Both passive and active immunity have a role in prevention and treatment. Active immunity through vaccination is the most robust and long-term way of protecting against a pathogen. Passive immunity can be used in severe cases of disease or in high-risk individuals who need heightened immunity after exposure.