How much protection do you currently have against COVID-19? The answer depends on so much: whether you’ve already had COVID-19 (and if so, how long ago); whether you’ve been vaccinated (and if so, how ...

A complement C4 (also known as a complement component 4, or simply C4) is a test to measure the level of C4 proteins you have in your blood. These proteins play a role in how your immune system ...

Complement component 3, often called C3, is an essential protein of the immune system. This protein plays a vital role in the body’s innate immune system, providing: the first line of defense against ...

With new COVID cases in Florida on the rise, taking an easy-to-get rapid test can give you quick results. But the timing has become tricky. If you have COVID-19 symptoms, such as fever, cough, ...

Federal regulators have authorized a new at-home test that can detect COVID-19, the flu, and other respiratory ailments. They say the test can help prevent the spread of these illnesses. They note, ...