Every living person has trillions of microbes living in their digestive tract, and more than 400 species of bacteria in the gut, more than the number of cells in the body. The normal gut flora is ...

What Are Active and Passive Immunity? Your immunity grows stronger when there are antibodies to illnesses and diseases present. Antibodies’ purpose is to damage or kill foreign organisms that enter ...

Your immune system defends your body against infections and illnesses. It makes proteins called antibodies that counteract or kill germs, like viruses and bacteria. You get protection, or “immunity,” ...

You’ve probably heard the term “herd immunity” used in relation to the COVID-19 pandemic. Some leaders — for example, Boris Johnson, the prime minister of the United Kingdom — suggested it might be a ...

William Petri receives research funding from the NIH, the Gates Foundation and Regeneron Inc. When COVID-19 first began spreading, public health and medical experts began talking about the need for ...