SARS-CoV-2, like many other pathogens, needs to be at a certain vaccine dose in order for it to trigger an infection and immune response in an infected individual. A low dose may allow an individual to respond to a virus successfully, while a dose that is too high can potentially make a person critically ill. Besides the amount of dose of the virus, another important factor affecting how successful a viral dose may be is the sum of the viral doses one receives over a period of time. Exposures such as in a healthcare setting can have a potential to expose a person to a higher dose of the virus over time, yet at the same time, wearing a mask may ‘lower’ the dose of the virus. Finally, a person’s pre-existing health conditions affects how much dose he or she can withstand. It is unethical to study the exact viral dose needed to make a person sick, so only animal models are used to predict viral doses. For more information, read the full article on CNN by Dr. Sanjay Gupta and Andrea Kane here.