The COVID-19 pandemic has led to a lot of questions around how the immune system works and how to support it with nutrition. While vaccines work by driving our immune response against the pathogen, a lot of its prevention strategy also depends on our own natural immunity. The efficiency of our immune system also determines how fast or good a vaccine works on us. Hence, just like we have been doing during the pandemic, we should also take earnest steps to keep our immunity up. Certain circumstances such as old age, stress or an inadequate diet affect the immune system's ability to react, making us more susceptible to infections.
One of the most studied effects on probiotic bacteria is boosting effect in immune response that is shown in a reduction of the incidence of infections, less severity, better response to vaccines, etc.