Simply understood, active immunity is our immune system fighting against pathogens to protect us. Passive immunity is gained from someone else that gives us protection from a pathogen. It is interesting to know that there is a third type of immunity – community immunity, which does not involve the physical components of our immune system but still provides protection. To dig deeper into the active vs passive immunity discussion, read on.
Understanding Immunity
Immunity is understood as the ability of our body to protect us from a pathogen that causes an infectious disease. When we are immune to a disease, it implies that we have developed the capability of fighting off infection causing that disease.
We are born with immunity that is natural and this is called innate immunity. We are born with this immunity and it stays and protects us for life. Our skin, our tears, and our stomach acid are the external or first-line defences that act as physical or chemical barriers. Our internal defences act immediately when a pathogen has entered our bodies. Inflammation and fever are examples of our internal defence mechanism at work.
Immunity is also acquired. This is known as adaptive immunity and protects us from a specific pathogen. This pathogen-specific immunity has two arms – active immunity and passive immunity.
How Do We Get Active Immunity and Passive Immunity?
Active immunity is acquired by us when our body is exposed to a specific pathogen. Exposure to a pathogen triggers B cells, a type of our white blood cells, to create y shaped proteins. These y shaped proteins are antibodies with the capacity to bind onto the toxins or pathogens, also known as antigens. Our antibodies attack, destroy, or neutralise the disease-producing pathogen.
Harbour no illusions! This active immunity does not happen immediately on exposure to the pathogen. It may take days or weeks for your body to acquire active immunity against a specific pathogen. However, once your body has kicked off this active immunity within itself, this is likely to last your lifetime.
Passive immunity is an antibody that is not created within our own body but outside. Thus, to get passive immunity, we need no exposure to a pathogen or disease-producing agent. Passive immunity acts on an immediate basis. On the flip side, passive immunity is temporary and does not stay and protect you for long periods.
Difference Between Active Immunity and Passive Immunity
While active immunity and passive immunity are both acquired immunities, they are different entities; both serving the same purpose i.e., protecting us from disease. The primary difference between active immunity and passive immunity lies in the presence and absence of memory cells. Active immunity is developed through the production of antibodies by our B cells, subsequent memory cells develop automatically that remain part of our immune system. This imparts lifelong protection against attacks from the same pathogen. The term ‘protection’ is what fundamentally differentiates between active and passive immunity.
Both active and passive immunities are pathogen-specific. Both are obtained either naturally within our body or from external sources.
Our active immunity comes from our own immune cells after exposure to infection/antigen. Pre-birth, as a foetus, our passive immunity [antibodies] passes on via the placenta from mother. Post-natal, it grows through breast milk [colostrum]. The difference between active and passive immunity, even naturally obtained, thus begins at their source itself.
The external source types also differ for active and passive immunity. Vaccination is the source of active immunity. Vaccines introduce an attenuated pathogen (pathogen kept live and modified to harmless form) into our body. The body mechanism performs its normal function to grow active immunity through B cells to generate antibodies and memory.
Externally, medication and injections are the sources of passive immunity. They act on the pathogens present in the body, and once withdrawn post-cure, the immunity gets over. Proteins created in a laboratory are also used for the treatment of certain diseases, especially cancer. These are known as monoclonal antibodies and have recently been used in drugs as passive immunity against COVID 19 (SARS-COV-2) virus. Animal antibodies, antibodies from infected persons, and even synthesised antibodies are introduced into our bodies to fight certain infections as passive immunity. These are generally termed ‘immunoglobins’. Passive immunity for poisonous snake bites comprises an admixture of antibodies to fight specific snake venoms.
Community Immunity – A Glance
There is nothing physical about community immunity. It is immunity provided through many protected people around us that prevent a pathogen from spreading on to us. It works best for children and those with compromised immune systems (suffering from other diseases). This is also referred to as herd immunity.
Conclusion
It is never active immunity vs. passive immunity. It is simply immunity to conquer infections and fight out the pathogens attacking our bodies. Passive immunity is an aid to active immunity and not against it. Together, they are our immunity.
