Vaccines don’t work on everyone. There are people who do not develop immunity from them. And even for those who do, immunity wanes over time.

The truth is, we simply don’t know how long a vaccine will provide immunity.

Compare that with getting ill from a “wild” strain of measles or chickenpox, wherein recovery ensures lifelong immunity. Why is that the case?

Our bodies were designed to fight infections. Each of us has a marvelous immune system that can recognize an infectious agent and produce antibodies against it.

In the case of measles, we contract the virus via exposure to infected droplets. It enters the body through the mucosal membranes where the immune system begins to produce antibodies.

Once the immune system has destroyed all remnants of the measles virus, it retains a memory of the antibody.

This memory — a stored immunity — becomes activated any time the body comes into contact with the measles virus, rendering the virus harmless forever.