Vaccines aim to mimic natural immunity. By exposing the body to harmless imitations, they create an immune memory, teaching the body to recognize infections from disease-causing pathogens. When an infection is recognized, an immune response is mounted, with antibodies latching onto the invaders and preventing them from causing illness. T-cells, which can attack pathogen-infected cells, are also crucial to the body’s defences.
All vaccines, including the COVID-19 vaccines, produce an immune response, but the strength of that response, and the duration of the resulting antibodies, varies depending on the effectiveness of the vaccine.
Added to this is the extent to which the virus or bacteria mutates or evolves. A rapidly evolving infectious agent may become able to evade the body’s defences if it looks sufficiently different to previous incarnations or finds new methods of attack. And creating a vaccine against a rapidly evolving enemy is like trying to hit a moving target.
We see examples of this each year with flu season. As the influenza virus replicates, small changes can emerge in its genetic make-up. This can lead to changes in the virus’s surface proteins, which are key to our immune system’s ability to recognize infection and trigger a response. This so-called antigenic drift usually produces viruses fairly similar to their predecessors, and antibodies created against one flu virus will probably still recognize and respond to similar viruses.
However, these small changes can accumulate, hampering our immune response to newer virus iterations and making a person susceptible to flu infection once again. For this reason, flu vaccine “recipes” are tweaked each year to make them as effective as possible against the viruses circulating at the time.
This content was originally published here.
